This is my first ECM car so I am very new to computer controlled cars. My other car is a 74 Pontiac SD455 Trans AM. No ECM there!

I am getting about 22mpg with mostly highway driving. My goal is to get around 27mph highway. What can I do to get the millage up?

I bought one of those "performance chips" things that are really a potentiometer. I have not installed it because I cannot find out where the IAT wires are. Does this thing even work?

Are there any REAL performance chips on the market for my car? My G35 is an early 2003.

 

Get an Osiris tune from UpRev

 

that "chip" does nothing. Return it if you can, otherwise throw it in the trash. replacing your spark plugs and getting a tune will be the best bang for your buck MPG-wise, but with the early 03 its very possible that your ecu isn't supported by uprev's reflash program. Check your ecu and if its black its good to go, grey no good. There was just a thread on this a little while ago and I posted pictures comparing the two..

 

That "chip" will likely fry your ECU like coke did to Chris Farley's nostrils.

 

On the old motor whcih had 220k+ miles & before my new motor swap i was getting an average between 26-28mpg's in my 03 sedan, running Mobil 1 5w30 oil, Motul rear diff fluid, and with ngk iridium plugs, Injen Cai, and Megan Ypipe, with Coupe Mid pipe & stock Sedan muffler. This was just back in April 2012 on a trip from Pensacola, Fl to Oklahoma City on cruise control 77-78mph on Interstate driving, and was getting 19.5-21 mpg's in the city.

 

32mpg for me.

 

^^ the digital fuel eco is not accurate..

 

Alignment and tire pressure could affect your MPG, but I don't think you'll get another 5MPG from that.

I've found that really having good control of your throttle helps quite a bit. Aggressive driving = poor gas mileage.

 

I'm getting 27-28 highway after doing the exhaust

 

I had a neighbor with a laptop and program to increase my total ignition advance to an additional 2 degrees...I get consistently 27.2 mpg driving 71mph turnpike over a 200 mile range...I do this all the time and figure if I drove slower I could do even better.
In the future if gas prices continue to move up I will be buying 255-45-18 REAR tires which will effectively reduce my rear axle ratio for a slight increase in mileage...I think we are looking at $4.00 gal (reg.) in the future
and last I run one tank of 89oct. when half full I then fill with 93. and back an forth...the car never pings and runs like a bandit.

 

^the "program" you are referring to is Cipher by Uprev.

 

Maybe if you cleaned the dust off your dash you'd get another 1 mpg

 

The only really accurate way to calculate mpg is to keep track of gallons filled vs miles driven and doing some good old fashioned math... the computer isn't that accurate and can be manipulated. Especially since yours is showing 458 miles till empty means that you just filled up and are probably going downhill or with a big tail wind.

My on board computer shows 50-60mpg consistently. Oh wait, I don't have stock injectors LMAO

 

Using this method I am averaging anywhere between 25 and 27 MPG per tank. It's possible. The best I ever averaged was 29 MPG on a whole tank.

 

That "chip" is just a resistor that overrides the sensor, sending a signal that tells your ECU that it's constantly a low temperature outside, probably something around 66°. This in turns changes how the car will run, mainly dealing with the timing.

http://www.gassavers.org/showthread.php?t=2831

Get the Uprev Osiris and get a real tune.