need help with gas milage
Thread Starter
Teching In
Joined: Jan 2011
Posts: 5
Likes: 0
From: Crystal River Florida
need help with gas milage i have an 01 stock z28 and i usually fill up at about 1/4 tank. When i first got the car i would get about 210 to 220 miles (from full to 1/4). I changed the spark plugs at about 95000. I put in bosch platinum plus 2 plugs and almost right away i noticed i was only getting about 160 to 170 (from full to 1/4) and straight highway driving wasnt much better. A few weeks ago i put in acdelco irridium plugs and changed the fuel filter and im still getting the same bad milage. any suggestions as to what else might be killing my milage?
I would not suspect two different plugs would give you poor mileage. If you have access to a scanner, you might look into how healthy your O2 sensors are. They usually degrage over time, and at 95k, may be a good place to start. Other ideas:
1) Cold weather, cold start enrichment, idling to warm the car
2) Oxygenated / Winter Blend Fuels
3) 1/4 Tank on the gauge isn't entirely accurate. Have you actually calculated your mileage from the distance traveled/gallons consumed?
4) Driving Style
All the combined changes may be just enough to drag your mileage down a few MPG's
1) Cold weather, cold start enrichment, idling to warm the car
2) Oxygenated / Winter Blend Fuels
3) 1/4 Tank on the gauge isn't entirely accurate. Have you actually calculated your mileage from the distance traveled/gallons consumed?
4) Driving Style
All the combined changes may be just enough to drag your mileage down a few MPG's
Thread Starter
Teching In
Joined: Jan 2011
Posts: 5
Likes: 0
From: Crystal River Florida
its been doing this since about may 2010 and i live in florida so there isnt a lot of cold weather. I even filled up with ethenol free gas a few times and still no difference, and my driving style is a little bit easier then it used to be, and when it gets to 1/4 tank it usually takes about 10 to 10.5 gallons to fill back up every time. so i guess the only thing left to do is check the o2 sensors. if they were bad would my check engine light come on?
Staging Lane
Joined: Nov 2005
Posts: 52
Likes: 0
From: Knoxville, TN
It all depends on the level of degradation. You should fill up your tank, reset your trip counter, drive until 1/4 tank. Fill it back up to full, take what your trip counter says and divide by how much you put in to get a more accurate measurement in miles per gallon. I know you're waiting until a 1/4 of a tank but 1/4 tank is very qualitative.
