How does your real MPG compare to the cluster display?

I’m running stock size Toyo AT3 on my truck, but you bring up an interesting point. I know many have had their speedometers recalibrated for larger tires, anyone here know if recalibrating the speedo affects the rate that the odometer will log miles?

Also, no need to run the truck to empty to calculate your MPG, just set a trip odo when you fill up, and divide the miles from that trip by how much gas it takes to fill back up next time you hit the pump. I rarely worry too much about my daily driving miles, but I always track it when I got for a longer trip for my own curiosity.

 

My Tacoma is too old to have that feature, but I've used it on 3 other vehicles. The 2009 Honda was consistently optimistic and by a significant amount. 3-5 mpg was the norm. It would show 38-40 mpg and the actual mpg would be closer to 35 mpg.

My wife's 2020 Ford Explorer is much closer. It is consistently 1-2 mpg optimistic. It will typically show 26 mpg but hand calculated it is usually 24-25 mpg.

My 2014 F150 is pretty accurate. I've owned the truck for 8 years and I've put 140,000 miles on it. The truck was 2 years old with 17,000 miles when I bought it. I used to manually calculate every tank, but I generally trust the readout now. Occasionally I still double check, but the readout as never been wrong by more than 1 mpg. And most of the time it is either exactly right or within 1/2 mpg. That's close enough.

Ford has a feature that will let you calibrate the readout to be more accurate. If you are consistently getting mpg readings that are off by 5%-10% etc. you can recalibrate the setting by whatever percentage the readout is incorrect. I've never done it because both of my Ford's are close enough.

 

24 and 25 mpg?might?? Really? If I average 15 to 18 I feel extremely lucky. My 21 off road has always been extra thirsty.
What's your secret to that mileage?

 

My 2016's dash estimate is pretty close running stock tires, usually less than 1 mpg off when I do the math.

The distance to empty is off my 15-25 miles though... I can run that far past 0/please refill. But I still feel like I'm rolling the dice running that low...

 

MPG claims vary so much with the Taco. I think since it's already piss poor economy, location and conditions have a far larger impact that other vehicles.

While I've never seen 24, 20 is doable if you're on county roads, don't use cruise control, and stay under 60mph. I also see far better mpgs in the mountains vs the flatlands, mostly from lower speeds and more coasting.

 

You know, now that you say that I noticed on our last trip to Colorado that my MPG Avg was better according to my indicator, than when driving around at home. I think you're right. I wonder if its because they were designed or geared for that type of environment or is it the coasting, or some third thing? It is interesting though.

 

It’s actually the rolling resistance of the tires that affects fuel economy. When a tire rolls, it flexes, and the flexing causes the tire to heat up due to internal friction. This heat is lost energy that reduces efficiency.

There are also aerodynamic losses.

It is true that a heavier tire requires more energy to accelerate, but the added weight (including rotational “weight”) is small compared to the total weight of the truck. Also the extra energy is only lost when using the brakes, thus it is even less significant on the hiway.

 

I have only checked mine on long runs between fill ups when pulling our travel trailer on trips. My display is generally slightly under what my fill up to fill calculations were. The display indicated less than a gallon worse mileage than the fill up calculations. Close enough for me not to bother with fill up calculations when traveling.

 

The original post is a fair bit higher than my typical MPG, daily driving I’m usually seeing more like 18 to 20 or so. My everyday conditions are a mix of city streets, usually without a ton of traffic given my schedule, and short distances (1-12 miles) at a time on the highway in between to get across town or run errands before work. I run a restaurant in Detroit and there’s never any shortage of random trips to make constantly to pick this or that up from whoever.

This particular trip in my post was mostly lower speeds off the freeway, where I was covering serious miles on my way up to a pretty rural/remote area, while also having flexibility to coast at least a good third of a mile to intersections/lights/stop signs regularly. Add in the very few vehicles on the roads, and coming up to speed more slowly than when driving in more congested areas, and it really adds up. If I didn’t live in the city I’d baby it like this on the daily but I don’t see any need to impede traffic to squeeze out an extra 65mi +/- per tank.

I think my tires being factory size helps a lot here, I will say I’m also pretty aware of my tire pressure and tend to check all the way around manually once every couple weeks, and every time I go on a trip that’s over a couple hundred miles.

Back to tire size, I have no reason to go larger currently, being that all the trails I run in my state are more roots and sand/logs than rocky, boulder-littered areas like I see out west.

Literally a case of YMMV, and not trying to flex on anyone but really just curious what everyone else is getting here relative to their built-in display, or how much variation others see.

 

I would agree that bigger tires, heavier tires, wider tires, not to mention increased wind-drag from lift, increased weight from sliders, a different unsprung weight (sometimes better/sometimes worse), stock gears, all play a factor in MPG.

I guess what I am wondering, and my theory, would be that the truck calculates MPG based on axle rotations x diameter of tires to get a distance. So I would guess, that by lifting, adding weight, and putting on "taller" tires, you are getting worse MPG than stock, but probably not as bad as the truck is telling you because it thinks you are still on stock/shorter tires. I mean... that's not profound or anything, but comparative MPG is rarely apples to apples. There are a gajillion different truck configurations and as many environmental factors that come into play.

Whenever I start thinking too much about all the above, I just remind myself that I didn't buy it for the amazing MPG. Hahahaha.

 

My 2018 is pretty damned close to actual measured mpg - usually within .3 to .5 mpg. After a bunch of manual calculations I came to the conclusion that was close enough for me. I regularly get 22-24 mpg on road trips, but wind, speed and hills are the biggest mpg killers. Highest ever was just over 28mpg on a ten hour drive going over three mountain passes but with the speed being limited generally to 40 to 50 mph for the entire trip due to heavy rain. After several hours it sort of became a contest with myself to see where I would end up by the time we got back to L.A.

 

You would be correct, and from my understanding speedometer corrections for tire size changes does not fix odometer readings, so you're pretty much stuck with it. Your average mpg readout on the truck is always going to be based on OEM tire sizes. This is also why so many folks hand calculations are still incorrect, because they still use the odo for their travelled miles. You need to run a GPS trip tracker or hand calc your mileage from a map if you want to accurately, or at least more accurately hand calc mpgs.

I do know that your estimated range is NOT based on your current mpgs and is instead based off your average mpgs since your last fillup. So if you were getting an average of 20mpgs on your last tank but now you're towing a trailer your estimated range is going to be a ways off. It does try to correct itself as you go through the tank, but it doesn't get it "right" until your next tank.