Need advice on how to get better MPG.

[General Stalin]

People make up waaayyy too many myths about high octane fuel. High octane means one thing and one thing ONLY:

High octane fuel is just gas that better withstands pre-ignition. Performance engines have advanced timing and high compression ratios than normal engines. Because of this, normal octane gas (or 87) would actually ignite too early because the high performance engine compresses it too much. This causes knocking/pinging and all that fun stuff. High octane gas has compounds in it that resist ignition, so it can be compressed more before igniting.

That's it.

 

[cam3439]

Yes this is true, but if you have ANY pre-ignition/detonation before the piston is all the way up then you have WORK AGAINST the engine and thus less fuel economy. A higher octane will lessen, if not eliminate, the pre-ignition/detonation that happens before the piston's full compression stroke. BEFORE the BB tune my truck ran more efficient at 89 than at 87, so that's what I used. The engine's idle smoothed out quite a bit and I noticed more miles per tank than with 87. I haven't tested the mpg's since my 93 BB tune, but we'll see what happens.

 

[General Stalin]

Well, these engines in our trucks were all engineered and designed to run efficiently on 87 octane fuel. They are not high compression engines, and the reason why BB tune requires the use of higher octane fuel is because he advances the ignition timing so the spark comes just a LITTLE bit later to compress the fuel/air just a LITTLE bit more to get a tad more power out of the power stroke.

 

[WoldD90]

Other than driving responsibly, keeping your tires inflated properly and keeping your speed down, there is not much you else you can do.

The e-fans did not do much for me on my 6.0, but they did on my LR Defender. The K&N helps the breathing a bit, but I have not noticed any huge gains.

 

[Fyrcaptain]

Absolute best hiway I have ever gotten was 19.8....I say 20 cause it makes me feel good. That's using regular gas, resetting the mileage computer right as I get on the hiway, a/c on, fully loaded, 38psi in the tires.
I drive it 95% hiway but my 5% round town is in the 14's.

It's a battleship, I don't give a shit what the fuel mileage is, I didn't buy it for that as my daily driver beater gets 27 city. Even if gas goes to $7, I'll still keep it cause it ain't my daily ride.

 

[Eagle]

narrower tires, lighter wheels.
I picked up about 1-2 mpg CITY when I switched down to 20s, I bet I'd pick up another 1 on 17s.
I get a little better MPG on 88 vs 86. I run about 1/2 a tank and then alternately fill up with 86 or 92 at Sams... their premium is the same price as 86 elsewhere so it isn;t costing me anything extra to run premium or a mix.

Honestly it feels a little dead on 86, I think it is pinging slightly and going to a very conservative "poor fuel" map. I'm already 10% down on power at 3500 ft. ASL.

 

[gtbigup01]

It seems like it doesn't matter what people drive they always ask what to do to get better gas mileage. I traded in an 04 Infiniti G35 to get this truck and i got 18 MPG agressive city driving on tthat car (rated 20/27) and was pissed I didn't get 20MPG, now driving like miss daisy I get 15MPG on my truck. Man do I miss my G35. Well not for the gas mileage, just that this is my first automatic I ever owned, I went test driving sticks last week just for the fun factor Mazdaspeed3, VW GTI, Subbie WRX, oh man!!!!!!!!

 

[JoeOmerta]

Things to ask yourself...

Is your mileage above 80,000?

If so,
When was the last time you replaced your:
o2 sensors?
spark plugs?
spark plug wires?
air filter?
gear oils?

Changing all of those can potentially help your fuel economy. I say potentially b/c every vehicle is different and results may vary.

What are your driving habits?
Heavy foot, light foot, do you let the car warm up before driving anywhere?
(by warmed up, i mean the car switching to closed loop)

What size rims do you have?
A smaller rim size is easier to turn compared to a larger wheel.

What pressure do you keep your tires at?
For ideal ride conditions and overall longevity of the tires, 34psi is recommended. On long highway trips it can be pushed to 40psi+ but be wary of load ratings and what the tire is capable of handling.

When was the last time you cleaned your MAF and throttle body?


I would say for a once over great tune-up(if these things haven't been taken care of already)...
1) Put a bottle or 2 of sea foam in a full tank of gas and run it down to 1/4 tank or so.
2) Clean the MAF with an electrical component safe cleaning solution(i use crc)
3) clean throttle body with throttle body cleaner(i use an old tooth brush to scrub it)
4) Run a can of sea foam in the intake system
5) change oil
6) change spark plugs + wires
7) change all 3 gear box fluids
8) change trans fluid/filter
9) make sure tires are properly inflated
10) change forward o2 sensors

If you have a vehicle with 80,000+ miles on it and those things haven't been done, you will notice a nice difference in mpg and performance

 

[blrmkrl83]

2005 Denali XL. 9.6 MPG at 100MPH. How's that. Speed does make a HUGE difference. I get 18 MPG at 70 and about 14.5 at 85.