New Motor Oil Geek: Transmission and Gear Oil Analysis at 5000 miles on Tacoma

[Andrace]

The interesting part is how “physics and chemistry” always get cited as proof, while actual measured durability improvements remain mostly theoretical.

Nobody disputes that a thicker oil can provide a thicker film under certain conditions.

The debate is whether that translates into meaningful real-world durability gains in this engine beyond what Toyota already validated.

That’s the part still missing.

I can't think of anyone, or a company, that would front the bucks to quantify that. So it's an easy position to take because there will never be evidence to "disprove" the logic, but absence of evidence isn't evidence of absence.

I remember my high school auto teacher saying Ford would change the tooling on a part if it would save ten cents each. So I asked a GM development engineer if that was true, and he said "idk about 10 cents, but if I could save 25 cents I'd go from being on a team to managing a team"

I asked for an example, and he said they determine how much aluminum is needed in a radiator by loading the vehicle to full gross weight rating and running it under full load up a long grade in the california desert at 105 degrees plus. They go thinner and thinner on the radiator cores. After the engine overheads and blows up, they go back up one size and if it passes the test, boom that was the minimum amount of aluminum they would have to use in the radiator for production.

The idea that the OEM performs exhaustive testing and recommends based on the customer's interest is la la land.

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[DENNISD]

I can't think of anyone, or a company, that would front the bucks to quantify that. So it's an easy position to take because there will never be evidence to "disprove" the logic, but absence of evidence isn't evidence of absence.

I remember my high school auto teacher saying Ford would change the tooling on a part if it would save ten cents each. So I asked a GM development engineer if that was true, and he said "idk about 10 cents, but if I could save 25 cents I'd go from being on a team to managing a team"

I asked for an example, and he said they determine how much aluminum is needed in a radiator by loading the vehicle to full gross weight rating and running it under full load up a long grade in the california desert at 105 degrees plus. They go thinner and thinner on the radiator cores. After the engine overheads and blows up, they go back up one size and if it passes the test, boom that was the minimum amount of aluminum they would have to use in the radiator for production.

The idea that the OEM performs exhaustive testing and recommends based on the customer's interest is la la land.

I don’t think anyone is claiming OEMs are altruistic or that cost engineering doesn’t exist. Of course it does.

But there’s a pretty big leap from:
“manufacturers optimize costs”
to
“their oil recommendations are basically meaningless.”

Your radiator example actually proves the opposite point. They tested to failure, established the minimum acceptable durability threshold, then added margin back in until it survived the defined operating conditions.

That’s engineering.

And importantly, they didn’t just say:
“Physics says thicker radiator cores are better, therefore thicker is automatically superior.”

They validated where the performance threshold actually was.

That’s exactly the missing piece in a lot of these oil discussions.

Nobody disputes that higher HTHS can theoretically increase film thickness under certain operating conditions. The question is whether that translates into meaningful measurable durability gains in this specific engine versus the tradeoffs Toyota already evaluated.

And that’s where the conversation usually shifts from measured outcomes to assumptions.

Also, “absence of evidence isn’t evidence of absence” cuts both ways.

It also means the absence of proof that 0W-30 materially improves long-term durability is not evidence that it does.

 

[BLtheP]

I don’t think anyone is claiming OEMs are altruistic or that cost engineering doesn’t exist. Of course it does.

But there’s a pretty big leap from:
“manufacturers optimize costs”
to
“their oil recommendations are basically meaningless.”

Your radiator example actually proves the opposite point. They tested to failure, established the minimum acceptable durability threshold, then added margin back in until it survived the defined operating conditions.

That’s engineering.

And importantly, they didn’t just say:
“Physics says thicker radiator cores are better, therefore thicker is automatically superior.”

They validated where the performance threshold actually was.

That’s exactly the missing piece in a lot of these oil discussions.

Nobody disputes that higher HTHS can theoretically increase film thickness under certain operating conditions. The question is whether that translates into meaningful measurable durability gains in this specific engine versus the tradeoffs Toyota already evaluated.

And that’s where the conversation usually shifts from measured outcomes to assumptions.

Also, “absence of evidence isn’t evidence of absence” cuts both ways.

It also means the absence of proof that 0W-30 materially improves long-term durability is not evidence that it does.

Can we cut through all this and discuss what you think the real world result of running 0W-30 would be? Even if it didn’t improve durability, does it matter? Surely you don’t think it will hurt durability?

Increasing HTHS and the resultant film strength increase that comes from doing so is exactly what improves protection. There is a point of diminishing return like anything else in life, but in most use cases going to 0W-30 will ONLY help.

The OEM already “validated” 30 grade oil for the rest of the world, so there is really no need for this discussion to endlessly go on and on and on about it.

 

[JayTech]

I get everyone has their own opinion on what oil they think they should run but do we really know better than the people that design these engines? If it is just your daily driver/commuter to work, I see no reason or real benefit in running anything but the recommended oil viscosity. Changing the interval is up to you, and there are no real demerits to changing oil sooner other than costing you a little extra money in maintenance.

Now where I think running a thicker oil might be better, is if you are constantly putting the engine under high load or operating in hotter climates that never see freezing temps. Is it more likely to shear out of grade than 0w20? Sure. Is it a concern? Not really. Just use high quality oils and keep up on your maintenance schedule and everything should be just fine. My rule of thumb has always been, "go up in grade, reduce service interval." If you do your oil changes every 5k anyways, unless you are getting that engine extremely hot ALL the time, you are not likely to shear out of grade. Also, 5w30 is thicker than 0w20, so even if it shears out of grade, it is still thicker than 0w20.

 

[BLtheP]

I get everyone has their own opinion on what oil they think they should run but do we really know better than the people that design these engines? If it is just your daily driver/commuter to work, I see no reason or real benefit in running anything but the recommended oil viscosity. Changing the interval is up to you, and there are no real demerits to changing oil sooner other than costing you a little extra money in maintenance.

Now where I think running a thicker oil might be better, is if you are constantly putting the engine under high load or operating in hotter climates that never see freezing temps. Is it more likely to shear out of grade than 0w20? Sure. Is it a concern? Not really. Just use high quality oils and keep up on your maintenance schedule and everything should be just fine. My rule of thumb has always been, "go up in grade, reduce service interval." If you do your oil changes every 5k anyways, unless you are getting that engine extremely hot ALL the time, you are not likely to shear out of grade. Also, 5w30 is thicker than 0w20, so even if it shears out of grade, it is still thicker than 0w20.

Isn't that contradictory? Do what the owner's manual says, except when you decide not to do what the owner's manual says? Driving at high load and/or operating in warmer climates that don't need 0W-20 is pretty much the entire point of all these conversations - making an educated decision on when following the owner's manual doesn't make sense.

 

[JayTech]

Isn't that contradictory? Do what the owner's manual says, except when you decide not to do what the owner's manual says? Driving at high load and/or operating in warmer climates that don't need 0W-20 is pretty much the entire point of all these conversations - making an educated decision on when following the owner's manual doesn't make sense.

I never said anything about the owners manual. After saying the engineers know best I gave my personal opinion. My opinion not being based on the oil itself but on how the engine would be protected. There really isn’t any need to change viscosity, but if you operate under “extreme conditions”, switching to 5w30 can provide the engine with better protection. That isn’t saying 0w20 can’t be used, or that it won’t be able to protect the engine, it’s just in that instance, 5w30 is better. 0w20 is more than acceptable as the engine was designed to use it, but it’s proven science that thicker oil is better in hotter conditions. It’s why before emissions made engines all run these thinner oils, owners manuals used to have operating ranges and different viscosities for different temperatures. That’s why in my opinion, if you just daily drive it there’s no need to bother with changing the viscosity but if you operate your truck in more extreme conditions, switching to a thicker oil wouldn’t hurt and can actually help. Especially with things like oil deposits in your turbo.

 

[DENNISD]

I never said anything about the owners manual. After saying the engineers know best I gave my personal opinion. My opinion not being based on the oil itself but on how the engine would be protected. There really isn’t any need to change viscosity, but if you operate under “extreme conditions”, switching to 5w30 can provide the engine with better protection. That isn’t saying 0w20 can’t be used, or that it won’t be able to protect the engine, it’s just in that instance, 5w30 is better. 0w20 is more than acceptable as the engine was designed to use it, but it’s proven science that thicker oil is better in hotter conditions. It’s why before emissions made engines all run these thinner oils, owners manuals used to have operating ranges and different viscosities for different temperatures. That’s why in my opinion, if you just daily drive it there’s no need to bother with changing the viscosity but if you operate your truck in more extreme conditions, switching to a thicker oil wouldn’t hurt and can actually help. Especially with things like oil deposits in your turbo.

This is probably one of the more reasonable takes in the thread because you’re no longer arguing that 0W-20 is inadequate — just that a thicker oil might offer advantages under certain severe operating conditions.

That’s a much narrower and more defensible claim.

Where I still disagree is the jump from “theoretically advantageous” to “better protection” as if it’s already been demonstrated in this engine.

Yes, thicker oil generally maintains viscosity better at elevated temperatures. Nobody disputes that. The missing piece is evidence showing that translates into measurably improved wear, durability, or reliability here in the real world.

If 0W-20 were struggling in these trucks under normal hot-weather use, towing, or highway operation, we’d expect to see a pattern emerge — failures, TSBs, revised specs, warranty actions, etc.

That’s exactly what happened in the GM example people keep bringing up.

So I think the more accurate position is:
5W-30 may be acceptable, and possibly beneficial in certain edge-case operating conditions — but it has not been demonstrated to be broadly superior to the validated spec.

That’s a very different argument than what a lot of this thread has been claiming.

 

[JayTech]

This is probably one of the more reasonable takes in the thread because you’re no longer arguing that 0W-20 is inadequate — just that a thicker oil might offer advantages under certain severe operating conditions.

That’s a much narrower and more defensible claim.

Where I still disagree is the jump from “theoretically advantageous” to “better protection” as if it’s already been demonstrated in this engine.

Yes, thicker oil generally maintains viscosity better at elevated temperatures. Nobody disputes that. The missing piece is evidence showing that translates into measurably improved wear, durability, or reliability here in the real world.

If 0W-20 were struggling in these trucks under normal hot-weather use, towing, or highway operation, we’d expect to see a pattern emerge — failures, TSBs, revised specs, warranty actions, etc.

That’s exactly what happened in the GM example people keep bringing up.

So I think the more accurate position is:
5W-30 may be acceptable, and possibly beneficial in certain edge-case operating conditions — but it has not been demonstrated to be broadly superior to the validated spec.

That’s a very different argument than what a lot of this thread has been claiming.

Has it been proven on this engine? No not yet and probably not likely, so you are right that this may not apply. But why I mentioned the whole under “extreme conditions” thing is simply because the oil itself will begin to break down once it reaches a certain temperature, which it can then leave deposits or protect the engine less causing more wear. 0w20 being a thinner oil, will begin to break down sooner than 5w30 at extreme temperatures. But I’d wager to say 99% of people are never operating their trucks at those kinds of temps and loads for sustained periods to where it would ever be necessary. At that point it’s just peace of mind really.

 

[DENNISD]

Has it been proven on this engine? No not yet and probably not likely, so you are right that this may not apply. But why I mentioned the whole under “extreme conditions” thing is simply because the oil itself will begin to break down once it reaches a certain temperature, which it can then leave deposits or protect the engine less causing more wear. 0w20 being a thinner oil, will begin to break down sooner than 5w30 at extreme temperatures. But I’d wager to say 99% of people are never operating their trucks at those kinds of temps and loads for sustained periods to where it would ever be necessary. At that point it’s just peace of mind really.

That’s a much more reasonable position, honestly.

I don’t disagree that, in a purely theoretical sense, a thicker oil may maintain its viscosity margin better at extreme temperatures and loads. That’s basic tribology.

Where I’ve pushed back is when that gets presented as if it has already been demonstrated to produce measurably better outcomes in this engine under real-world use.

And I think you just clarified that pretty well:
for the vast majority of owners, 0W-20 is likely entirely sufficient, and moving thicker is more of a personal “peace of mind” choice than something supported by clear durability data.

That’s a very different claim than “Toyota only recommends 0W-20 because of CAFE” or “5W-30 is objectively better.”

I think that distinction matters.

 

[GSPHerder]

Well Dennis there's those who believed fauci and took all the vaccinations and are still probably driving around with covid masks, same peeps who believe everything that is in the manual in addition to what jackass Texas Toyota engineer who was all over utube touting the new 4th gen until axles started snapping then he disappeared.

Then there's those that aren't afraid to think out of the box and rely on data instead of what another bean counter is feeding them.

 

[DENNISD]

Well Dennis there's those who believed fauci and took all the vaccinations and are still probably driving around with covid masks, same peeps who believe everything that is in the manual in addition to what jackass Texas Toyota engineer who was all over utube touting the new 4th gen until axles started snapping then he disappeared.

Then there's those that aren't afraid to think out of the box and rely on data instead of what another bean counter is feeding them.

And now we’ve officially left the oil discussion and entered political meme territory.

For the record, I’m not arguing that manufacturers are infallible. Axle issues, recalls, and spec revisions absolutely happen. The GM bearing example already proved that point.

What I am saying is that “thinking outside the box” still requires evidence.

Right now, the argument for thicker oil in this engine mostly comes down to theoretical advantages at extreme temperatures, personal preference, and anecdotal reports. That’s fine, but it’s very different from proving Toyota’s validated spec is inadequate or inferior.

Ironically, the “trust the data” crowd keeps presenting assumptions, pressure screenshots, one-off UOAs, and regional charts while dismissing the largest real-world dataset available: hundreds of thousands of engines successfully operating on the specified oil.

That’s the disconnect I’ve been pointing out this entire thread.

 

[BLtheP]

I never said anything about the owners manual. After saying the engineers know best I gave my personal opinion. My opinion not being based on the oil itself but on how the engine would be protected. There really isn’t any need to change viscosity, but if you operate under “extreme conditions”, switching to 5w30 can provide the engine with better protection. That isn’t saying 0w20 can’t be used, or that it won’t be able to protect the engine, it’s just in that instance, 5w30 is better. 0w20 is more than acceptable as the engine was designed to use it, but it’s proven science that thicker oil is better in hotter conditions. It’s why before emissions made engines all run these thinner oils, owners manuals used to have operating ranges and different viscosities for different temperatures. That’s why in my opinion, if you just daily drive it there’s no need to bother with changing the viscosity but if you operate your truck in more extreme conditions, switching to a thicker oil wouldn’t hurt and can actually help. Especially with things like oil deposits in your turbo.

I agree with every bit of this. What I took issue with in the first comment was saying to trust the engineers who designed it and saying you see no real reason to change viscosity. Then in the next paragraph it said mentioned possibly upping the viscosity based on conditions (which I do agree with and which is what me and most others in these discussions have these discussions for). Anyways, that was the contradiction I was talking about.

To me trusting the engineers and running the recommended viscosity generally means running only what’s in the owner’s manual, which is why I brought the manual into the discussion.

My opinion is that “the engineers” don’t make most of the decisions and it comes down to the marketing department to decide what actually goes in the book. The engineers allow a range of what will work and the marketing team elects what actually is recommended based on the other criteria (fuel economy, emissions, ownership cost, expected durability, etc.)

The viscosity temperature chart that they used to put in the manual was far too logical. These days the one size fits all approach makes much less sense, but that’s what we get for letting the governments call all the shots.

 

[BLtheP]

This is probably one of the more reasonable takes in the thread because you’re no longer arguing that 0W-20 is inadequate — just that a thicker oil might offer advantages under certain severe operating conditions.

The distinction you’re trying to make is smaller than you think. If a thicker oil offers additional thermal stability and film strength under load, then by definition the thinner oil offers less margin in those same conditions. That doesn’t automatically make 0W-20 inadequate, but it does mean there are tradeoffs involved that should be considered.

Yes, thicker oil generally maintains viscosity better at elevated temperatures. Nobody disputes that. The missing piece is evidence showing that translates into measurably improved wear, durability, or reliability here in the real world.

If the oil gets hot enough that viscosity and film strength fall below what the engine needs, the damage is already occurring. You don’t wait until failures become widespread to acknowledge that margin matters. There is nothing to dispute about that. You are not maintaining proper durability if the oil thins out too much to do its job. IF the cooling system is good enough to prevent that from happening, then we probably won't see too many problems in the long run. But that's the thing, too many manufacturers these days, including Toyota, ride a very thin line as far as margin of protection goes.

If 0W-20 were struggling in these trucks under normal hot-weather use, towing, or highway operation, we’d expect to see a pattern emerge — failures, TSBs, revised specs, warranty actions, etc.

Again, you don't want to actually get to this point. If 3 years from now Toyota proclaims that oops, 0W-20 turned out to be inadequate, go ahead and switch to 5W-30, wouldn't you be concerned about the long term damage that was done over those years? This is NOT how the system should work, because at that point the damage is already done. This is not me saying damage WILL happen on 0W-20, but it is me saying that if it were to get to that point, it wouldn't be good for owners that had been using what Toyota all of a sudden decided was no longer good enough.

So I think the more accurate position is:
5W-30 may be acceptable, and possibly beneficial in certain edge-case operating conditions — but it has not been demonstrated to be broadly superior to the validated spec.

That’s a very different argument than what a lot of this thread has been claiming.

I say again, does it really matter if we prove this? We don't need to prove it. The whole point of oil is to provide a margin of protection. How much margin? Well, choose your viscosity for that. It's not about "better," it's about how much margin you want. 0W-20 provides the level of protection Toyota deemed acceptable for balancing durability, fuel economy, emissions, and operating conditions. That doesn't mean it's ideal for the owner long term. Is it ideal for the owner? We don't know until years down the road and we see how reliability panned out. Many people will make it well beyond the warranty period, because 0W-20 is not totally inadequate. However, there will be people who fall outside of that boundary and they won't know until it's too late. Because of that, some people want to ride a bit further away from the line between adequate and inadequate, which is why they run a higher viscosity.

Nobody towing a heavy trailer in extreme heat has ever been told: “you should probably switch to a thinner oil for extra protection.” Why? Because viscosity margin under heat and load matters. That’s basic lubrication physics, even if we can’t produce a 300,000-mile controlled study proving exactly how much benefit a thicker oil provides.

Nobody is claiming 0W-20 is instantly destructive or incapable of protecting the engine. The point is simply that increasing viscosity increases film strength and protective margin under heat and load. Toyota already approves thicker oils for this engine in other markets, so the idea that we need to prove anything for 5W-30 is silly and unnecessary. Some owners are comfortable running the minimum acceptable viscosity for efficiency reasons, others prefer a little more protection margin for towing, heat, or long-term ownership.

 

[DENNISD]

The distinction you’re trying to make is smaller than you think. If a thicker oil offers additional thermal stability and film strength under load, then by definition the thinner oil offers less margin in those same conditions. That doesn’t automatically make 0W-20 inadequate, but it does mean there are tradeoffs involved that should be considered.



If the oil gets hot enough that viscosity and film strength fall below what the engine needs, the damage is already occurring. You don’t wait until failures become widespread to acknowledge that margin matters. There is nothing to dispute about that. You are not maintaining proper durability if the oil thins out too much to do its job. IF the cooling system is good enough to prevent that from happening, then we probably won't see too many problems in the long run. But that's the thing, too many manufacturers these days, including Toyota, ride a very thin line as far as margin of protection goes.


Again, you don't want to actually get to this point. If 3 years from now Toyota proclaims that oops, 0W-20 turned out to be inadequate, go ahead and switch to 5W-30, wouldn't you be concerned about the long term damage that was done over those years? This is NOT how the system should work, because at that point the damage is already done. This is not me saying damage WILL happen on 0W-20, but it is me saying that if it were to get to that point, it wouldn't be good for owners that had been using what Toyota all of a sudden decided was no longer good enough.


I say again, does it really matter if we prove this? We don't need to prove it. The whole point of oil is to provide a margin of protection. How much margin? Well, choose your viscosity for that. It's not about "better," it's about how much margin you want. 0W-20 provides the level of protection Toyota deemed acceptable for balancing durability, fuel economy, emissions, and operating conditions. That doesn't mean it's ideal for the owner long term. Is it ideal for the owner? We don't know until years down the road and we see how reliability panned out. Many people will make it well beyond the warranty period, because 0W-20 is not totally inadequate. However, there will be people who fall outside of that boundary and they won't know until it's too late. Because of that, some people want to ride a bit further away from the line between adequate and inadequate, which is why they run a higher viscosity.

Nobody towing a heavy trailer in extreme heat has ever been told: “you should probably switch to a thinner oil for extra protection.” Why? Because viscosity margin under heat and load matters. That’s basic lubrication physics, even if we can’t produce a 300,000-mile controlled study proving exactly how much benefit a thicker oil provides.

Nobody is claiming 0W-20 is instantly destructive or incapable of protecting the engine. The point is simply that increasing viscosity increases film strength and protective margin under heat and load. Toyota already approves thicker oils for this engine in other markets, so the idea that we need to prove anything for 5W-30 is silly and unnecessary. Some owners are comfortable running the minimum acceptable viscosity for efficiency reasons, others prefer a little more protection margin for towing, heat, or long-term ownership.

This is actually a much better argument than most of the thread because you’ve finally narrowed it down to “margin” instead of trying to claim 0W-20 is outright inadequate.

Where I still disagree is the assumption that “more margin” automatically translates into meaningfully better long-term outcomes in this engine.

Yes, thicker oil generally maintains viscosity better under extreme heat and load. Nobody disputes the physics behind that. But engines are engineered systems, not isolated viscosity charts. The relevant question is whether the specified oil already maintains sufficient protection margin under the overwhelming majority of real-world operating conditions the engine was validated for.

You keep framing it as though Toyota is balancing right on the razor’s edge of catastrophic failure, but there’s still no evidence that these engines are broadly struggling on 0W-20 in towing, heat, highway use, or daily operation. That matters.

And I think this is the key distinction:
you’re treating the absence of widespread failures as “we just haven’t seen it yet,” while I’m treating the absence of widespread failures after large-scale deployment as evidence that the validated spec is likely doing its job.

Those are fundamentally different assumptions.

You also said “we don’t need to prove it,” but once someone claims a different viscosity provides better protection, more durability, or better long-term outcomes, then yes — at some point evidence does matter. Otherwise every viscosity increase could simply be justified as “more margin,” indefinitely.

At the end of the day, I think your current position is much more reasonable than earlier claims in this thread:
0W-20 is likely sufficient for most owners, while some people prefer extra viscosity margin for peace of mind under sustained heavy load and heat.

That’s a far more defensible argument than claiming Toyota’s recommendation is fundamentally wrong.

 

[32spoke]

Not surprised at all. Careful though, I’m sure Mr Dennis d will be running along at any minute to tell you how you can’t prove anything else is better.

Yup, you ain’t wrong!! he came to defend his opinion with an ad hominem

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