Any ideas on increasing fuel economy without adversly effecting performance on my 2003 4.2 automatic? I have all pm up to date,drive conservatively. I teach auto for a living, I am wanting yo know what others have tried that I may have overlooked. I am not a big fan of reflash without dealer level equipment as I have seen many problems created with aftermarket tuners. I am currently averaging aprox.17 city, 20 highway

 

That's about as good as it gets. Just keep up with maintenance. EPA says 16 city 20 highway, if you are equaling that you are doing well, especially with ethanol in the gas.

 

Seriously, your doing about as well as the truck can do.
Review the thought that the computer system runs on a program that is self adjusting with feedbacks from sensors that do a compare to software tables where logic decisions are made then returns output control signals to the hardware as the corrections.
You can't break into the system from the outside with modifications that are detected by the PCM.
The usual result is the program makes changes trying to get back to the program 'table values' as the self correction that takes place.
The system largely negates the changes your trying to make.
Note that when corrections fall outside the table limits is when the codes are set to indicate the system is out of normal operating limits.
Only way to influence fuel mileages from 'outside' is to reduce weight, lessen rolling resistance, reduce parasitic losses that all result in less throttle being used to move the vehicle weight.
Only other way is to make changes to reduce the amount of fuel metered and advance the ignition timing within limits to fudge things a bit but it requires program changes to the tables, as mentioned above..
Good luck

 

Buy a Civic! LOL

 

I run 40 psig in my 265/70x17 stock size energy Michelins. It makes a difference. I also noticed an increase in mileage when I installed my Superchips 87 tune. The last time I checked my mileage carefully was right after a plug change and driving 800 miles from Wilmington NC to Homestead FL. Most of the trip I was on the interstate or turnpike with the cruise set on 80mph and I got 16mpg running it that hard, with a 5.4 and 4x4.

 

Increase aerodynamics (reduce drag)

 

Lower it. 3/5 drop

 

lower it!

went from about 14-15mpg in my 4x4 at stock height, to about 17-18mpg when lowered 4/6. I have seen 20mpg ONCE on the highway with my 87 performance tune.

 

Thats what I'm talking about! 4/6 drop getting 24 hwy

 

Lowering really is the best way in my opinion, even if you "use it as a truck."

Whodathunk I'd suggest lowering?

 

Get an Ultragauge or Scangauge. Actively watching your "instant" MPG and learning how it effects your average can make a huge difference in your driving habits and overall efficiency. Just by actively watching the gauge in my lifted '99 5.4 4x4 I'm able to get 18 mpg on average.

 

i wish.....i gotta keep outa the boost....

i get around 18 usually with a 2" drop all the way around...

 

I have the full ground kit which helps in the aerodynamics of better mileage..lol