What affects MPG the most?

Mythbusters did an episode on this a while back. They took 2 identical vehicles with identical amounts of gas and drove them around a track until one ran out. The one that ran out first was less efficient, and was the truck with the a/c on, windows up.

So is it more efficient? At least under some conditions, yeah, probably. But at a certain point your personal comfort needs to play a role, too. And not just the temperature, but the noise. Personally, I don't like to have to crank my radio to be able to hear it, so if I'm on the freeway, windows are up, no matter what the temp is outside. If it's 75 or 80 and I'm just cruising around town, yeah, windows are down.

If I'm out wheeling, windows are usually down, a/c off, but that's for other reasons, like being able to stick my head out and see obstacles or lessening the risk of overheating (slow speed, high ambient temps, a/c on = more risk of overheating).

If you're worried about trying to make your vehicle as efficient as possible, I would start by replacing your 4x4 pickup truck with a hybrid or a Tesla or something, lol.

 

Mythbusters has done a bunch of interesting tests for mpgs.

I have the 100% solution for improving my mpgs by double!

I either drive my car or my motorcycle everywhere I go and only drive the truck for truck stuff.

Between all three I average 35mpg.

 

The myth busters test only really works for the specific vehicle that they used. Being that the AC system in my truck was designed 20 years ago with longevity in mind, not exactly efficiency.

 

I believe the one thing that will affect mileage the most is any tire larger than stock.

Adding more weight with the cool stuff will just worsen the mileage.

Between A/C and windows being down, I’m going with windows being down on highway driving. Stop n go traffic, I’d go with A/C.

 

I was thinking something similar about my car.

I used to have a 2003 Honda Civic Sedan 5 Speed Manual, 110 torques, 115HP, 2500 pounds. When you turned the AC on you could feel the power drain.
I now have a 2016 Scion IM Hatchback 6 speed manual. 126 torques,137 HP, 2950 pounds When you turn on the AC you feel no power drain at all.

Could be that they're totally different cars or could be technology has changed or the focus is fuel efficiency vs longevity or all three or something totally different.

 

Myth busters did a show on this.

 

The specific vehicle is arbitrary. All they wanted to find out was if the a/c made a difference in efficiency, and if the loss in aerodynamics from open windows was enough to balance the decrease in parasitic drag on the motor. Any change is relative, all they want to show was it more or less efficient. The actual amount of change would depend on your vehicle.

Now, if your vehicle has an a/c system that functions fundamentally different, like on an electric car, then yes those tests are not valid. However that wasn't the point.

 

I can't remember if it was this forum, or another one, but I remember many years ago, people were getting all hot and bothered about hypermiling their vehicles and bragging about getting 25mpg out of their tacomas (for example). Someone chimed in with "I get 70mpg while doing 0-60 in 4 seconds"

Yeah, that was a motorcycle.

Anytime one of those hypermiler threads shows up on a tacoma forum, I just have to giggle a little bit.

 

Ok ladies and gents,

Just wanted a thought conversation regarding what people think, not myth busters. I know they have shown some cool stuff but just wanted to see what people thought

I also prefer the windows down, ac on, music loud, and ear plugs in. Gotta hear later in life.

 

inflate those tires, give it a full tank and see where it takes you
they are the 'normal' size tire for your truck?

 

Every test I ever saw states AC is the best just because of the turbulence with windows open.

I have a Truck it pretty always has a load.

Come to think of it I have never closely checked fuel mileage of any vehicle I owned big truck got about 7mpg pick up around 10 to 12 was as close as I checked

 

You're right, the vehicle was arbitrary,b that doesn't change the fact that older AC systems aren't as efficient as a newer system. I can definitely feel a power drain when my AC is on. I don't feel the same slowing as when my windows are down.

 

The truck came with 275/75R16 tires.

New spark plugs a couple weeks ago.


And after this picture I realized the plastic cover is cracked. Fun!

 

my truck has 15s ... so your's are the proper size for a 2oo4 model?

i am approaching 350 miles on my current tank of gas of approximately 16 gallons, which is about average i have always normally gotten

 

does anybody know if 'tire brand' plays any particular role in MPG
or are all tires basically the same as far as efficiency goes

 

Depends on your speed. At lower speeds the A/C affects milage more. At higher speeds windows will affect milage more. Not sure where they cross over, but definitely at freeway speed you will be better off with A/C on.

 

This list came from the owner manual:

 

Not sure if brand makes a difference but definitely tire type (summer vs winter vs off road), comparing similar sizes.

 

I was quite upset when I got these winter/mud/highway combo tires in December and then could barely manage 280 miles on a tank of gas in January/February/March

but it could've been a combo of being in 4wd more than normal, breaking new tires in, more stop and go driving in 4wd than usual, under inflated, or really crappy gas at the BP/Shell, which are 'supposed' to have quality fuels

 

That is a substantial difference! I know winter has changes to meet EPA emission standards which effect those mpg's.