alright last wk i had flushed out the radiator to put new coolant in, and before i did any of that, on a full tank of gas i would get around 300 miles or more, now after i did all the work of cleaning out the coolant and putting new coolant, i now get around 280 what happend? i used prestone dual formula antifreeze/coolant? plzz help what did i do wrong??

 

Dude you need a tune up. Mine gets over 400 on a full tank. Spark plugs, fuel filter and air filter should do it. Oh and some good fuel injector cleaner.

97 Maxima GLE

 

The only good fuel injector cleanoer you can get is either paying $60+ to get the injectors cleaned or buying new injectors. Don't waste money on any of that crap they sell at autozone or stores like that. I also really doubt you replacing the coolant had ANYTHING to do with the change in gas mileage. Also a difference of 20 miles to a tank is nothing to worry about. Hell, you could've just gotten hard on the gas pedal a few times and cause that change.

 

Dude... you had a difference of 20 miles per tank. Do you realize that that is about 1mpg difference then what you had? Which probably means you got on the gas two or three times more than you did in the previous tank.

There is no way you're going to drive exactly the same from tank to tank, fluctuations happen. You also have to realize that changing coolant has NO RELATION TO GAS MILEAGE.