What am I not understanding about MPGs ?

[Deleted User 412290]

So I obviously I lost a lot of efficiency moving from stock 245s to 275/70R18 with a 1.5" / .5" lift, but if I drive around like my grandma all week in town I average maybe 14+. Yet today when I was running errands I decided to test it driving like a 19 year old with a WRX and I got 16.1. What gives ?

(mostly just an excuse to post another photo of my truck)

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[GSPHerder]

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)

 

[EatMyTaco]

Were you driving a different mix of driving types? Colder or warmer outside? That kinda thing.

im getting 19-20mpg mixed driving average, and it has less than 400mi on it. I dunno what I’d need to be doing to get 14 unless I was driving uphill in wind with a heavy load in the bed.

 

[Deleted User 412290]

All controls have been the same around here. No highway driving. I get 19-20 there. Tires are big, but not huge, and they're SL, so not too heavy either.

 

[StreeTaco]

Thanks!! We almost forgot what it looked like

 

[Deleted User 412290]

Thanks!! We almost forgot what it looked like

 

[EatMyTaco]

Could be less fuel used due to less turbo if you’re putting more foot in it and causing a higher gear to be picked by the transmission.
I’ve noticed when I put it in manual mode on a hill, as the rpm goes up, turbo output goes down. Less forced air requires less fuel to keep it from being too lean. Higher gear 7 vs 6 for example, more turbo output = more gas sprayed per ignition to keep the mix from being too lean.

im just theorizing here. Not stating facts, more just an educated guess based off of what I know about turbos.

 

[MJB4450]

Some organization, I forgot which, did a study on acceleration about ten years ago. They discovered that getting up to speed from a stop slowly actually uses more gas than getting up to speed quickly. Not drag race quickly but a lot faster than lollygagging up to speed.

 

[Deleted User 412290]

Some organization, I forgot which, did a study on acceleration about ten years ago. They discovered that getting up to speed from a stop slowly actually uses more gas than getting up to speed quickly. Not drag race quickly but a lot faster than lollygagging up to speed.

This checks out because I've been doing HELLA lollygagging trying to get good numbers. Let's see how some more spirited acceleration changes things

 

[theDLR]

Some organization, I forgot which, did a study on acceleration about ten years ago. They discovered that getting up to speed from a stop slowly actually uses more gas than getting up to speed quickly. Not drag race quickly but a lot faster than lollygagging up to speed.

to add to that I'd imagine once up to speed, you're coasting.

So visualize between 2 points that are 1/4mi apart from each other.

Point A, you're stopped.

Point B, you're 1/4 away.

First time you take the whole 1/4mi to progressively get to coasting speed. The whole time your vehicle is accelerating, constant change in your velocity and effort the engine/turbo is outputting.

A second time you go WRX style, and 50ft later you're already at coasting speed. so you've let your foot off the gas, and engine isn't needing to work as hard and shifts into a lower gear.

So then...

turbo output goes down. Less forced air requires less fuel to keep it from being too lean.

 

[trailhunger]

to add to that I'd imagine once up to speed, you're coasting.

So visualize between 2 points that are 1/4mi apart from each other.

Point A, you're stopped.

Point B, you're 1/4 away.

First time you take the whole 1/4mi to progressively get to coasting speed. The whole time your vehicle is accelerating, constant change in your velocity and effort the engine/turbo is outputting.

A second time you go WRX style, and 50ft later you're already at coasting speed. so you've let your foot off the gas, and engine isn't needing to work as hard and shifts into a lower gear.

So then...

I’m not buying the study. Michu Kaku: takes the same amount of energy to cover that distance in the exact same amount of time. The variable is air resistance, if the engine is to temp, time (perceived faster but in reality took longer), braking, etc

Albert Einstein is rolling in his grave. From a complete stop to crossing the end point at the exact same elapsed time, explain how the laws of physics can be defied & you get free gas by goosing it off the line vs driving like grandma.

 

[theDLR]

I’m not buying the study. Michu Kaku: takes the same amount of energy to cover that distance in the exact same amount of time. The variable is air resistance, if the engine is to temp, time (perceived faster but in reality took longer), braking, etc

Albert Einstein is rolling in his grave. From a complete stop to crossing the end point at the exact same elapsed time, explain how the laws of physics can be defied & you get free gas by goosing it off the line vs driving like grandma.

I see what you mean, fair point. So factoring that which i missed. I'd say then the lower MPG on the granny style run would point more to the truck staying in a lower gear whereas in WRX mode the tranny might upshift sooner getting into a taller gear + convertor lock where the engine is then able to cruise at the lower rpm. There's definitely a lot more variables take into account like someone else mentioned air temp or wind speed, road grade, tire temps, traffic, etc. We're really just identifying surface level explanations in a non-controlled testing environment.

We didn't even identify driver weight, maybe I ate at a buffet for thanksgiving and swallowed 300lbs (losing approx 1 mpg / 100 lbs of weight) of food, and the tryptophan from the turkey is why i caught myself granny driving.

 

[oxi]

Well, I have the 6MT. I notice when running granny or short shifting into gear, the turbo kicks in more to get up to speed. Also, when I get to highway speeds and lock it into 6th gear, I hear the turbo constantly kicking on as soon as I even touch the throttle.

I'd like to run in 6th gear to lower overall rpm's but turbo input is more frequent. Though, keeping it in 5th gear runs a higher rpm but less turbo input at speed. Such the dilemma on the highways. So, for highway speeds, I am still trying to master the difference between running 5th and 6th gear with the turbo.

On commuting to work and back, mostly back country roads, I have learned to just run it normal shift patterns, no short shifting keeping rpm's higher up so I am not catching gears thus turbo input. I try to minimize any unnecessary turbo input.

I actually hit 18 to 20 mpg depending on wind and winter conditions with larger and heavier 265/70 KO2's.

Looking at my legendary Camry for reference, during the long below zero cold spell, I dropped down to around 36 mpg for the hybrid/gas combo due to the extreme cold with soft WS-90's.

Now that some warmer weather popped up, I gained all the way back up to 42 mpg, thus gained 6 mpg alone with temps outside. Weather plays a huge role. In the summer with factory 18's and stiffer Continental's the Camry should be between 46 to 48 mpg.

Results are: weather and wind play huge roles in mpg's, your tires are next and then driving habits. Though with a handicap transmission, more difficult to overcome vs a manual I would suspect. With these trucks we will never figure out the mpg's and that is why I typically do not bother with it. I focus more on using the turbo less with my driving.

 

[franx]

With my Limited Hybrid I have been averaging 20-23mpg on my 30 mile commutes to work. Once in a while I hit 25-26mpg, but thats not too common. Only 5200 miles on it so I am hoping it gets a little better once broken in.

 

[Ironhide]

So I obviously I lost a lot of efficiency moving from stock 245s to 275/70R18 with a 1.5" / .5" lift, but if I drive around like my grandma all week in town I average maybe 14+. Yet today when I was running errands I decided to test it driving like a 19 year old with a WRX and I got 16.1. What gives ?

(mostly just an excuse to post another photo of my truck)

Similar situation. Leveled the truck and went to a 275/70R18, my mileage took a massive drop to 15.1. At the time I didn’t change my driving habits. This past week I got to thinking perhaps the difference of tire size change to speed ratio might be playing a part in it. I reduced my speed following a ratio calculator and I’m back up to 16.5.

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