Gas mileage decrease on M20?

[CharlesAFerg]

Lately I have been noticing a significant decrease in gas mileage, without changing my driving habits. Are there any common issues in a high mileage M20 that could potentially cause such changes? I have gone from ~15.5avg to 12.9 in a matter of a few weeks.

I know there are many, many things that can affect gas mileage, but if anybody has thoughts, PLEASE share them. I'll be selling to car soon, and eventually replacing it with another E34. (Don't worry, I still love 'em.)

Help!

[ahlem]

Are you using your OBC to come to that conclusion? You need to take an actual calculation based on actual miles and actual gallons. Then you need to check your fuel pump to see if it's dying. When mine was starting to go I went from 18.7 to 15.7 around town on the OBC but was actually getting 18.7. Have you done a compression test? You should be getting much better mpg than 15.7

[CharlesAFerg]

Hmm, I need to perform a compression test. Do I have to take it to the mech to have this done?

[CharlesAFerg]

I'm going to be doing some educational engine work myself this weekend now that finals are over.

Here are some things you all should know.

*For months now, I have been fouling plugs up front, oil fouling. Within a few months, they would be fouled again.

*I have a lot of oil/dirt on my intake manifold cover, and some drop lines running down below my oil cap.

*I am planning on just taking the dive and getting much of this figured out on my own, while I'm at it, at least.
eg.. adjust valves, replace the intake manifold gasket, what else? What about the valve guide seals?

PS.. does anybody have a "lachsilber metallic" drivers side fender? I have an extra one, but it's slightly darker silver, which isn't what I need...