What am I not understanding about MPGs ?

[shackley]

You’re 100% right. Everything is out of wack with anything other than the OE size. The average mpg is just an estimate anyway. More like a shameful reminder of what my mileage could have been before the upgrades. Just using a rough 2-8 mph addition to what the speedometer reads. If it reads 50, Im actually doing about 54. 60, I’m going about 65. And 65, I’m probably knocking on 72.

To calculate MPG with different tire sizes, first determine the old and new tire diameters. Then, use the formula: New MPG = Old MPG × (Old Tire Diameter / New Tire Diameter) to find the adjusted miles per gallon,

This is why I went from Trailhunter OEM = 265/70/18 to 285/70/17 and lighter wheel but same diameter and ultimately lighter unsprung weight and have about the same mpg = 18.6 in town and 19.5 highway if I keep my speed at or below 75 mph.

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[shackley]

Higher rpm/lower gear/ more efficient? I feel that lower gear ratios generally get better gas mileage because it requires less throttle. (to a point of course)

What's with that with Tacomas? I had a Jeep Gladiator Rubicon with 4.10s, but most increased it to 4.56 or 4.88 or more. No one seems to be doing that at least with Trailhunters and Pros with 3.58. Would my TH get better mileage with 4.10s or are we so computer bound that it wouldn't work? Sorry for going off on a tangent, but coming from a Rubicon I find it vexing.

 

[shackley]

You’re 100% right. Everything is out of wack with anything other than the OE size. The average mpg is just an estimate anyway. More like a shameful reminder of what my mileage could have been before the upgrades. Just using a rough 2-8 mph addition to what the speedometer reads. If it reads 50, Im actually doing about 54. 60, I’m going about 65. And 65, I’m probably knocking on 72.

Use this: https://tiresize.com/wheel-offset-calculator/

 

[shackley]

I imagine it would have to do with the efficiency of the engine under various loads vs time. Yes, you're using more fuel when accelerating quickly but accelerating slowly for a much longer period may not be as efficient as quickly for a short time. An example would be that V8 engines are far more efficient than a 4 cyl when you measure mpg vs hp. A 400 hp V8 may get 20 mpg while a 4 cyl engine half the size would not get 40 mpg, more like 30 mpg. So in this example the V8 is 50% more efficient than the 4 cyl. when comparing cubic inch or hp. vs mpg.

I've had 6 Tacomas since 1999. Varying my driving habits on the 1 Gen DID make a difference, but then the computer contribution was essentially nil. I keep wondering if it's fighting the computation in these 4th Gen Tacomas.

 

[Ironhide]

Use this: https://tiresize.com/wheel-offset-calculator/

Thanks! That’s my go-to site for info and a visual comparison.

 

[GSPHerder]

What's with that with Tacomas? I had a Jeep Gladiator Rubicon with 4.10s, but most increased it to 4.56 or 4.88 or more. No one seems to be doing that at least with Trailhunters and Pros with 3.58. Would my TH get better mileage with 4.10s or are we so computer bound that it wouldn't work? Sorry for going off on a tangent, but coming from a Rubicon I find it vexing.

I agree, spent the morning trying to source a gear set for the 9.5" rear and 8"ifs front. I can find 4.3's for one but not both. Definitely gonna be my first mod before a tune. I'd might even go lower but cant find a set with matching ratios for both front and rear.

 

[shackley]

Thanks! That’s my go-to site for info and a visual comparison.

And why I chose the tire/wheel combination. OEM wheel/tire weight was about 73 lbs. With my Black Rhino Etosha at 24.6 lbs, and Nokian Outpost nAT at 46 lbs (Discount says 47) = about 70-71 lbs, and diameter about equal, BUT my MPG didn't increase measurably, but I only have about 1500 miles on it, so I'll keep tracking. I've always used E series tires, so I'll be interested to see what airing down will do.

 

[shackley]

I agree, spent the morning trying to source a gear set for the 9.5" rear and 8"ifs front. I can find 4.3's for one but not both. Definitely gonna be my first mod before a tune. I'd might even go lower but cant find a set with matching ratios for both front and rear.

With my Rubicon, I could change the diff ratio with a computer. I assume you could do that with Tacomas, but I've never done that with them. Otherwise, the mileage will be way off going from 3.58s to say 4.10s. Let me know what you do, and who in ABQ/Rio Rancho does that.

 

[GSPHerder]

I dont think changing the ratio with a computer will help. The stock 3.5's is way to high for my tastes and pretty convinced its for their ratings than more for real world. Soon as you put some real world NM wind and hills on it your mpg tanks.

I'll do the math after the change and dont really care what the dash says. I'll have it figured in my head.

 

[shackley]

I dont think changing the ratio with a computer will help. The stock 3.5's is way to high for my tastes and pretty convinced its for their ratings than more for real world. Soon as you put some real world NM wind and hills on it your mpg tanks.

I'll do the math after the change and dont really care what the dash says. I'll have it figured in my head.

Sounds good.

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