xxxcnhxxx

I need help. When I first got my a4 I was about 50% hwy driving and getting 330 mi per tank. Now I'm lucky to get 245. I installed a new fuel filter a few months ago. I cleaned off my maf and ait sensors with alcohol. I just put on a test pipe w nonfoulers thinking I had a clogged cat and realized white smoke from tailpipe. I don't think my head gasket is bad with no milky or foamy oil.

What other things should I check for my gas mileage.

ILovemyDula

Check your valve seals. Having the same issues @ 185k mi. seen it most on start up and at idling also in and out of first gear.

Zeca

Look into the PCV System...In my 2001 1.8T there were some issues with clogged/gummed up/"mushy" hoses and PCV pressure relief valve "thingy"....

It is said that this could cause bad gas mileage along with increased oild leakage through gaskets, and seals...

Just got done with the job...

Good luck

hellbringer

i noticed fuel improvements when making sure tire pressure and changed my front/middle and rear gear oil. I believe I had previous postings on this. But one warning, a few months after i changed my rear gear oil the new oil started to leak - since it's not as thick as the old fluid. I needed a rear diff seal replaced which cost me approx $500. But the car drives EXTREMELY smooth and I feel like I'm always hitting the brakes to slow the car down. Love it!

You can always try to draft

hellbringer

also assuming you checked spark plugs

mtroxel

How long have you had the white "smoke"? I don't have to tell you that's a big clue. I'm thinking compresson test.

Past that, these are all just guesses, and parts are really expensive. You want to get to the bottom of this you could have a VAG-COM for less than $200...or for about the price of your average Audi part.

4Driver4

Coolant Temp sensor.

Any codes?

4Driver4

How to check these and how would they contribute to poor fuel economy?

xxxcnhxxx

No codes .... Vagcom is telling me nothing. Coolant temp sensor replaced last year. Any way to test the occasion system?

Reggie

So you need to provide more info. Miles /years on plugs?
Have you tried BG44K?

If you suspect the engine then a compression test and leakdown test will tell you about the mechanics.