91 or better octane highly recommended (as stated in the owners manual). A cold air intake and tune may help with MPG as long as you can resist the urge to keep your foot off the gas.

 

24miles per gallon. CITY (2004 limited auto, 95oct)

I live in Iceland and there are no straight roads, it's all up and down hills with traffic lights on all corners...
I think i might get it to 26/7/8mpg if i ease my foot on the pedal a little bit, change my 8yr old spark plugs and clean my throttle body.

I've used STP Fuel Injection cleaner a couple of times since i bought the car back in september 2011 and i've found little-ish improvement
in mpg both times. Maybe its just in my head :l

 

I'll have to give an honest try for mileage some day... all my gas mileage goes out the window between 2nd, 3rd and 4th. 2004 Silver blue 6spd Coupe. Annnnd........Loving it!!

 

Using 89 will it cause any knocking ? First thing I do when i get it gotta put in gas so I'm just wondering

 

Might, but the computer will probably just dial the power back until the detonation stops...

 

Unleaded premium is the recommended fuel for the XFire. I have a cousin that bought a Vette some time back and after owning it for a few years he called me & said it was running really lousy. I asked what gas was he using. He stated regular unleaded. Told him the Vette was suppose to use unleaded premium. Then I told him if he couldn't afford the gas, then he shouldn't have bought the Vette.

Logic holds true for the XFire, too! Not trying to give you a hard time - just passing along advice that will keep your newly acquired XFire performing like it was designed to do. Engine problems on these cars typically turn the XFire into a "throw away".

 

By the way, I typically get 22-23 mpg around town with the 07 Coupe. Highway performance is usually around 26-27 mpg. My XFire has the 5-speed Autostick. Originally rated at 21/28 mpg. I'm happy!!!

 

I dot see how you guys are getting these numbers, especially when these cars are only rated at 15 city from the factory (which is usually optimistic compared to actual on most cars). I get about 17 avg but thats about it no matter what I do. Oh well, its a fun 17 miles for each gallon! lol

 

These are the official window stickers.

 

Here's a copy of my 2007's original window sticker. You'll see the EPA ratings somewhat different than onehundred80's.

 

My second one lists the same mileage ratings.

 

He owned a vette a high performance car and didn't know he had to use premium?
That's kinda funny but i understand your not giving me a hard time , I knew it would take premium just was wondering what grade and if by chance I did put regular unleaded(which i never will) would knock occur
But thanks for the response , the engine stayed the same from 04 to 08 in the NA crossfire correct? Then how come the epa mpg ratings changed after comparing 180s pic to yours it doesn't make sense to me haha

 

fueleconomy.gov shows another different rating too, lol. I guess it just depends on the car, even from the factory. How's that for quality control??? haha This is definately a strangely quirky little car. Maybe a bit too quirky? Edmunds shows 15 city.

 

I just drove over the rocky mountains from Calgary Alberta to Vancouver British Columbia which is about 1,100 km each way. It is totally highway with very steep grades and averaged 110 km or 65 mph. I carefully logged the mileage at each fill and the car got 35 mpg. (Imperial gallons) That converted is about 29 US. mpg.
Cannot complain about that. The engine has a lot of torque which was very good on the steep long grades and never had to kick down from Drive. This is a far cry better compared to what it likes to suck up in the City. In the City I am lucky to break 20 mpg.

 

Something's wrong with your car gunner, you're either driving around in 1st gear all the time, driving 130 mph all the time, or one of the mods you or the previous owner did to the car is killing the mpgs.

Do you do most of your driving somewhere where you have to stop for stop lights every 30 seconds?

 

Usually a mix of stop and go and hwy. More hwy adds up to closer to 19 mpg more city 16. Usually avg about 17-18. Maybe I need a plugwire replacement? Car seems to run good though. I cant even seem to baby 20 out of her if I try so I just quit trying. I drive her like I want to now and try not to think too much about it. I do miss my Rumble Bee though, lol. I traded it partially because of the low mpgs of 14 city/18 hwy, which turns out to be what I get with the xfire. Oh well, live and learn.

 

There's definitely something wrong if you're averaging 17-18mpg in mixed driving. How many miles?

 

+1 I'd start with the simple things...air filter, for example, followed by a plug examination then a change, if needed...

 

Car just rolled 50K and has new plugs and air filter installed by me about 2K ago. I did notice when I washed my car that my right exhaust tip was a little sooty and black and the other was clean and shiny. I have true duals now, so maybe an issue on pass side bank with plug wire or ????. Definately need to check into it, but car is running good so unsure where to go from here. Any suggestions???

 

I've got the same thing going on, after a plug change about 2K miles ago...is there an answer?