My '99 V6 S-10 is losing MPG like crazy

This summer there was something obviously wrong with the AC. Loud noise came up everytime I used it, so we stopped using it until we could find a good mechanic. I noticed that my city MPG dropped from the usual 19 to 16.5 to 14.5 the last couple of fillups. Can't really afford a trade-in right now. Anybody have any idea what might be happening? I'd like to know what might be the story before approaching any mechanic.

Might be or could be any number of things.
But with out any more info than you have gave us you guess is as good as anybody's.
If you are going to a mechanic to get it fixed the worst thing you can do is to try to do his job for him.
Let him check it out and fix it for you.

The first thing I would check is the tune up end.
How many miles on last tune up?
Plugs filters and wires and so on?
What engine?
Any check engine lights or codes?

THe S-10 has about 92k miles on it. It's the V6 engine. There are no engine lights on. I'm not trying to fix the car, I'm trying to do what I can before seeing a mechanic. I'm surprised you mention wires as I wouldn't think that would give a progressive deterioration of MPG. Thought of plugs, of course, but didn't know those could go out like this. Can't remember last tuneup, if ever.

THe S-10 has about 92k miles on it. It's the V6 engine. There are no engine lights on. I'm not trying to fix the car, I'm trying to do what I can before seeing a mechanic. I'm surprised you mention wires as I wouldn't think that would give a progressive deterioration of MPG. Thought of plugs, of course, but didn't know those could go out like this. Can't remember last tuneup, if ever.

At 92 K it is about ready for a good tune up.
I would do that first.
As said it can be many things,
If you are going to a mechanic let him check it out.
Good Luck

Don't forget the simple things also like air filter, Leaking pressure regulator, low tire pressure.

If your decrease in mileage was sudden, you might have bought an ethanol blended gas. Your reduction in mileage is right in line with a 10% blend. Consumers report has a good story:

Quote:
"That’s because ethanol has a lower energy content than gasoline: 75,670 British thermal units per gallon instead of 115,400, according to the National Highway Traffic Safety Administration. So you have to burn more fuel to generate the same amount of energy."

http://www.consumerreports.org/cro/cars/new-cars/news/2006/ethanol-10-06/overview/1006_ethanol_ov1_1.htm

Our state AAA site lists ethanol free stations, but they are becoming fewere and arther away. See if you can find one and see if your mileage goes back up before you tear out your hair chasing a non-problem.

Might also want to check the AC compressor. Pull off the belt, or just loosen it, and spin all the pulleys to make sure all spin freely. You say you had AC problems already, maybe the compressor or compressor clutch is the culprit.

Might also want to check the AC compressor. Pull off the belt, or just loosen it, and spin all the pulleys to make sure all spin freely. You say you had AC problems already, maybe the compressor or compressor clutch is the culprit.

Nonsense, if the AC compressor or clutch failed as to such an extreme to cause that kind of a mileage drop there would have been a noticeable energy transference into something as simple as a loud noise or something more catastrophic such as a belt failure.

Might also want to check the AC compressor. Pull off the belt, or just loosen it, and spin all the pulleys to make sure all spin freely. You say you had AC problems already, maybe the compressor or compressor clutch is the culprit.

Nonsense, if the AC compressor or clutch failed as to such an extreme to cause that kind of a mileage drop there would have been a noticeable energy transference into something as simple as a loud noise or something more catastrophic such as a belt failure.

Nonsense, if the AC compressor or clutch failed as to such an extreme to cause that kind of a mileage drop there would have been a noticeable energy transference into something as simple as a loud noise or something more catastrophic such as a belt failure.
Yeah, ok. Tell that to the owner of the 2005 Taurus that just had it happen. Additional draw on the engine can and will kill your mileage and/or power. The Taurus I spoke of was driven 5 months before it wore out the belt.