Hi I have really bad gas mileage. It's been cut in half. I've taken it to the dealer and they can't find out whats wrong. Any ideas?! No engine light. Car runs smooth. Doesnt need a tune up. Spark plugs are fine. But still getting really bad gas mileage. Help Please!!!

Asked by Feb 17, 2016 at 04:28 PM about the 2009 Pontiac G6 GT

Question type: Maintenance & Repair

Hi I have really bad gas mileage. It's been cut in half. About 14 miles per
gallon. I've taken it to the dealer and they can't find out whats wrong. Any
No engine light. Car runs smooth. Doesnt need a tune up. Spark plugs are
fine. But still getting really bad gas mileage. Help Please!!!

12 Answers


Could be your coil is failing. My 98 Civic started to have rotten gas mileage and then just died on me after a stop sign stop. After the coil was replaced she ran just fine and dandy and got better gas mileage. Have your coil checked. It could be something real simple like that.


How many miles on the car? Check the engine compression and the catalytic converter. If your dealer can't figure it out, find a competent mechanic.

twinkiedooter. i dont think its the coil because i read on the internet a bad coil will just take the gas mileage down a little. Mines cut down by over 50%

full_of_regrets. i have about 43,000 miles on the car. the catalytic converter is fine. i got that checked out. how do i check engine compression?


Bad and/or failing coils mean gas not being properly ignited. I had really rotten gas mileage and not just 15% when mine went tits up. Whatever your problem is....it's definitely in the ignition spark area as the gas is not burning properly. Steer clear of dealers. Ask your friends to recommend a competent mechanic who has done work for them at a reasonable price. I have a guy who has a shop behind his home that fixes any and anything brought to him and he fixes it right. A good honest mechanic is VERY hard to find.. Did you buy this new or used?

i bought the car used a couple of years ago. so do you think dealer mechanics are a bad choice. it would seem to me that they would be the most reliable. whats ur opinion? how low was ur gas mileage when u were having problems and what should u have been getting mpg?

whats strange is the car seems to be running fine and no engine light on or anything. i asked another mechanic besides the dealer and he said he wouldnt even know where to start since the car is running smoothly.


This sounds weird but what brand of gasoline have you been using lately? Here in ohio they sell really crappy gas full of water. Marathon sells the worst gas but if you got a tank of bad gas your car would run shitty AND get horrible gas mileage as well I am not a big fan of dealership mechanics. Had a 74 brand new Toyota Celica and the manifold bolts would fall out every 500 miles or so and the dealer mysteriously could not fix but kept putting in more bolts. Ugh. Then my 76 Dodge B200 van had a main seal oil leak and only had less than 10K on it. Bought new. Took back to dealer TWELVE times before they really fixed it as they kept using some kind of cheapo "instant fix" i.e. gasket maker vs take the actual gasket/seal off and put a new one on. I'd get the van back and less than 50 miles would have to add a quart of oil....and you wonder why I a) don't buy new cars and b) don't take my car to a dealer. Ask your friends who they take their cars to and try to find someone who works on your model of car. My private mechanic has worked on lots of Hondas and he knows my car. I had a Jeep GCL and he fixed and changed just about everything on the SUV for me and did a good job until I sold her. Typical Jeep Money Pit. My gas mileage is usually near 24 or 28 and dropped down to less than 20 around town stop and I go less than 10 miles one way. I knew something was wrong but couldn't figure out what as I am a stickler for keeping gas tickets and writing my mileage down every time I fill up. A habit I've had since the 70's that has served me well over the years. My 94 Jeep GCL was a honey and gave me little problems over the 14 years I had her until she rusted out in the frame the summer of 14 and I got the money pit special a 97 jeep GCL. Had that for 15 month and bought my Civic around Halloween last year. I don't drive much - just around town and do maybe 250 miles a month now since I am retired. I always insist on WATCHING any mechanic work on my car. Dealers won't let you watch so I don't trust them one bit. I suggest you find the good mechanic in your area and watch him like a hawk when he fixes your car. Don't be the lazy man who just drops off the car and comes back later when it's done. Great way to have the shop rip you off for stuff not done or stuff done wrong to your car. I am 68 y/o and had a lot of expensive car repair lessons from a master mechanic that would let me watch him work. I spent many happy hours and a lot of money on the cars I had him work on in South Florida for 16 years before I moved. He didn't overcharge me and sometimes didn't even charge me for little stuff.....that's what an honest guy does. He is more interested in keeping a good customer vs rip off everyone that walks into the dealership and who cares if they ever come back.

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Sorry for the long post but I DID use paragraphs but apparently they don't show up on this site.

i use gas at murphys gas station. my uncle uses the same gas and doesnt have any problems. im not sure what other mechanic to ask . i've already talked to the two main mechanics in my town

do you think it could be a bad 02 sensor. i hear sometimes a bad 02 sensor doesnt cause the engine light to come on


02 sensor will always shoot a code. They're an emission requirement. And they never affect the way the car runs.

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