IRSmart

the mods that would affect gas mileage on my car are pypes longubes, off-road h, flowmaster super 40 stainless catback, and a canned tune. in my tune, my rear O2's are turned off and are not plugged in anymore. after my tune, i was getting around 15-17 mpg in the city. on my last tank, mixed highway and city (more city) i averaged 12.9 mpg. the car is driving normally, and the only thing that i notice that is different is that my exhaust smells different. i can't explain it, it just doesn't have the same smell to it anymore. i checked my oil and the level was good. i'm due for an oil change soon, so i was just going to go ahead and do it. my car has 99,800 on it right now. what do you guys think, just needs a tune-up or what?

DreamerGT

A tune up would be a good start.

IRSmart

just new plugs and wires, or what else would be involved? i was told by a buddy this weekend that i don't need to mess with my COPs until they break, is this true?

bluovalguy

Did you change the brand of gas you bought? Some stations refuse to use the 10% ethonal mix, and some do use it. If you were running straight gas before, and got a tank with ethanol in it, you would see a drop in mileage.

WannaBeGearHead

You did state that you drove more in town on this last tank of gas. More stop and go traffic could be the cause in your drop of MPG.

IRSmart

but i haven't changed my mix of driving. if anything, i've had more highway driving on that tank than anything else. i've been noticing a drop in fuel economy lately. i'm already down below 3/4 of a tank with 70 miles on the trip.

most stations around here use E10, so i don't know if that's the cause or not. i don't even know if the smell of the exhaust is related, i just figured it was worth meantioning. i have an XCAL-3, would it help to datalog the car? i've never done that before, and i don't know if logging the car will show that it is not running properly.

hpwrestler220

i was getting around 14-15mpg with city driving and maybe 17 with a mix.... i did a tune up (oil filter, air filter, changed the oil) and now im seeing 16mpg city..ill take it i guess. idk what im getting highway bc i rarely drive the highway. i dont need to

oh and you dont have any wires to change... that's why we have COP's. and no you do not need to change the COP's.. there is no need

MJH78

Well down here I get at least 2mpg less, on average, in the fall and winter months than I do in warm weather months. The reason being is I do a lot of short trips to work and back and an engine that's running "cold" is one of the big reasons for more gas consumption. So I reach my destination before the engine has reached full operating temp. Cold weather in general will cause a decrease in fuel mileage, even if the motor is at normal operating temp.

03BottleFedGT

check for an exhaust leak it could cause you to burn rich and smell worse. also bad gas milage

IRSmart

i do have an exhaust leak as a matter of fact. i asked the guy that put them on to use RTV sealant at every joint, he said he did, but it still leaks up at the driver's side. how can i fix that so that the leak goes away, other than tightening the bolts? is there like a caulk i can put around them to seal them up?