Greetings group,

I have a bone-stock '94 Z28 automatic that I've had since new. I've only used premium since I've had it and average mileage as of 2005 was between 250 to 310 miles per tank, depending on driving conditions.

I had to store the vehicle for 2 years for various purposes, and ever since it came out of storage it has been getting terrible gas mileage. On average, I'll see between 160-180 miles per tank, almost half the mileage I had before! Before I put the car in storage, I did a tune up changing the plugs and wires. The car otherwise drives perfectly fine. My mechanic says this could be caused by the additional ethanol in gas, but not sure if that's what it is. What else could this poor gas mileage be attributed to?

Thank you,

- Nes

 

Have your driving habits changed? Were you doing mostly highway driving before you put it in storage, and mostly city driving now?

 

What did you do to the fuel system before you put the vehicle in storage?

Have you ever changed the O2 sensors?

 

Negative; driving habits have not changed, I'm driving the same as before, just to work and highway on weekends.

Nothing done to the fuel system, nor I have never changed the O2 sensors on recommendation by the mechanic. He mentioned that if there was something wrong with them I'd get a check engine light. I suspected these should be changed at some point but not sure. I've only changed the fuel filter once on the vehicle.

 

I'd swap the fuel filter ASAP, and put some Berryman's fuel system cleaner in the tank. The gas that sat in it for those 2 years probably gunked it up pretty good. I've had my car sitting for 2.5 years until a month ago when I started a full drivetrain/engine build. When I replaced the fuel pump in the tank, I could see very clearly how nasty the old gas was from sittting. On a side note, I kept my tank low on fuel during it's storage period, and started the car at least every 2 weeks, but gas isn't made to last too long. Good luck!