re: Ot mechanics: gas mileage issue

Don't you have a bunch of kids?

Do you put them all in that focus?

If you are not going 100+ MPH, you are doing it wrong

You are basically getting -0.000 MPGs right now

A thicker oil requires more mechanical energy to pump it through the engine(which uses more gas) but it should only use maybe 1-2 mpg more. I'd get gas somewhere else and continue to monitor it.

My guess is the loss is due from switchover to summer blends.

Run a different brand of gasoline, assuming you use the same brand all the time.

Another issue may simply be wear, or your cats are getting more restricted.

Summer blend would make a change,
also may have to do with the oil,
no change in drive habits, more city?
Warmer weather lately running the a/c much?
check the air filter too...

My guess is a combination of using the AC more and possibly a shitty O2 sensor.

And as a hijack, I'm happy to report that my TDI is still improving at 27k miles. 49mpg average and climbing

Check to see what they filled you with.

0W20 is probably spec. Quicklube places used whatever they have on hand.

On small motors an extremely thick oil can knock an mpg or two off.

More than likely, it's in your head.

I can't remember if that motor has vvti or not. If oil actuated... Thick oil can make them run a little ... off.

quote:

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TDI is still improving at 27k miles

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First off, if you changed to a "high mileage" oil for no other reason than you thought 129k is high mileage, you done fricked up. High mileage oil just has extra seal swelling additives that might help with slight leaks around valves and front or rear main seals. You should notice that the API Service symbol on the bottle probably does not say "energy conserving" or "resource conserving" too. That's because these oils use additive packages that are outside the API service spec, usually more EP, VII's, and detergents. All good stuff if you care more about reducing engine wear than peak fuel economy and catalytic converter life. Problem is the seal conditioners will expand the seals a little and they will wear in to that condition, meaning you are stuck using a high mileage oil to maintain the seals in that new state. That's why you should not use such an oil unless you suspect a problem with oil control that could be helped using it. All that said, 50 miles in one tank means nothing if you changed fuel brands or a number of other factors. Keep checking for another few months.

Im no expert but I've heard oil can do that (not sure to what extent). If its running smoothly otherwise, try a different oil next time and see what happens I guess.