Hello everyone I have 07 coupe. My car is averaging just over currently 13mpg. I've had that car since November. When I got it it was averaging about 15mpg but since then I put an exhaust on the car and noticed that decrease. I feel like this is low sense most people on here claim about 19 mpg. I do mixed city and highway driving. I do get on the car at times and I understand that but I also have babied it at times to test my mpg and get basically the same mpg only about 1 mpg difference. And I do measure my mpg by miles driven/gallons burned using the odometer. Anybody have any ideas of what could cause my mpg to be so low? Also is this something any shop could check or should I go to the dealer?

 

A shop could check but I would start with a few basics. Air filter cleaned, check spark plugs for wear, are you using premium, are you putting the correct oil in it, scan for error codes. this should at least give you a starting point.

 

Winter gas uses ethanol partially so you get less MPGs but it is cheaper...

 

Thanks I appreciate it. I don't have any codes. I plan on changing my spark plugs soon just because it's a used car but im sure these arent worn the car doesn't miss at all. I only use shell 93 octane gas and I used mobil 1 motor oil when I changed it last month.

 

Yea im not really worried about the 2mpg drop im more so concerned with me getting 13 consistently where other people average 19 especially since I don't really beat the car on the regular

 

Your low gas mileage issue is common and obvious since it has resulted since you installed the exhaust system. What I'm posting is fact, there is no guessing here! You like the way the exhaust sounds, it's music to your ears so when you're driving your brain is controlling the throttle. You might be staying in gear a little longer or leaving a stop sign quicker but it's costing you gas mileage. Sure you could change spark plugs or do other maintenance but that will change little! Turn up you tunes and try to ignore that beautiful sound your ride is making..."Good Luck!"
Gary

 

Another mpg thread makes me a sad panda.

 

Thanks and I definitely understand that part but even before the what I was averaging about 15 without beating the car while other people claim 19 when beating it. So I was wondering if I could have a bigger problem like cats or o2 sensors

 

Yea I saw the different ones on here already but I couldn't find one that was an actual list of parts that cause low mpg mainly just pages and pages of people saying your driving too aggressively get off of the throttle

 

Have you had the ecu tuned. That's one thing ppl don't mention when they ramble on about their low mpg.

 

I had the same issue and im still trying to fix my mpg issue. These car are very finicky to gas mileage IMO thats why their are so many different gas mileage reading vary from different people.

Are you warming your car up in the morning? If so these cars guzzle gas at idle. Try to warm up the car for no more than 30 seconds then drive lightly until engine temp rises up.

Check if your car is slightly running too hot or cold. Are you fans on all the time? My car had a aftermarket thermostat that crapped out and i was running 30-40* over stock temps. After changing my stat my car ran less sluggish and my mpgs went up about 1-2.

Winter grade gas sucks *** for city drivers. Expect a 2-5 mpg loss in the city for that. My Acura TSX mileage dropped 3mpg due to the winter gas so its not just the G35s.

Are you running winter tires? More drag from tires can cause mpg to drop also.

Also (which I need to check on mine) check to make sure you dont have a stuck or frozen brake caliper. This can cause drag and lower hwy mpg.

 

You will receive error codes if there's anything not working correctly. One thing that helps mileage is using your cruise control whenever possible. You didn't post the number of miles on your G, if it's close to 100K you could be ready for plugs and all the other maintenance suggested at that mileage. Claims of 19 mpg probably include city/highway mileage and a close calculation of mileage from a full tank to the next.
Gary

 

Check it out:

All these weird things people talk about that are out of the ordinary are not things people do normally to get good mpg. Getting goof mpg has to do with maintenance and driving style.

Make sure you're up to date with differential, transmission and engine oil changes, keep your spark plugs changed every 40-50k (I don't care what anyone else says), keep your tires properly inflated, your air filter clean and don't drive 80 everywhere you go. Also, no red light romps on the gas, or excessive passing.

O2 sensors DO progressively degrade, but you wouldn't see a significant decline in mileage unless they were actually broken, so changing them now wouldn't result in much.

 

I haven't personally and I doubt the previous owner did the car is doesn't have any aftermarket parts except my exhaust

 

Wow thanks I actually warm my car up for about 15 minutes almost everyday. And no my temps are good and I have nankang ns2 Tires on the front and idk what tires are on the back but they look like performance tires