I have been getting 250 miles a full tank until the low fuel warning comes on for the past 3 tanks now. Its kind of upsetting knowing that i should be getting 360 AT LEAST! I have a 2004 5AT coupe, and i drive in mid city, highway conditions. I think the ecu revs high because i floored it at 50 miles when i got the car. I wanted to know if resetting the ECU help me save gas.

 

The mass airflow sensor measures the mass of air coming in and sends a signal to the ECU (which is also receving signals for a dozen other things) and sends a signal to the injectors telling it how much fuel to deliver. When you step on the gas, it sends a signal to the throttle body telling it how much to open it, which will determine how much air comes in.....which delivers the proper amount of fuel...etc. etc. Resetting the ECU will have absolutely no bearing on your fuel mileage. The ECU does not care how you drove it 50 miles ago. The tranny will care, but only to determine your shift points.

When your needle is buried on E, you still have 2 gallons left. Mid city, mid highway should give you somewhere between 15-20 mpg depending on your driving habits. Keep in mind that your mileage may improve and stabilize somewhere around 3000 miles-ish and that your gas gauge is lying to you. When they light comes on you still have around 4 gallons left.

If you have the Nav, look at your average speed. When my average speed is 22.5 mph, I get 14.8 mpg. When it is 24 mpg, I get around 16 mpg. 1.5 mph makes a big difference.

 

thanks this was very help ful, so i will test this out and go past the E, also i noticed when i start my car, say the needle is directly on the half mark it will go down halfway beetween the half mark and the next line, but after about 2 minutes of driving it will go back up, what is this phonemenon, i know it has to do with the gas resting at one place, but this is weird ot me since my 2000 maxima did not do this and they are both VQ's

 

What could possibly make you think resetting the ecu would make you save gas?

You should fill up the tank before it gets to E. Going lower stresses the fuel pump and could cause you too suck up crap if there is any in there.

The phenomenon you are talking about is how to engineer how to tell a driver how much fuel is in the tank in a moving vehicle. It's not simple. The fuel gage is an indication, it's not absolute.

2004 G35C 6MT Black. Sweet.