Oil consumption Q

[bazar01]

MY 93 with 94k miles after two years of ownership. I finally have been driving since springtime and have been monitoring the oil consumption. Consumption is about one quart for 1500 miles. Does this mean I do not have to worry about the valve guide problem these cars are well known for? If there is a valve guide problem, what mileage do they normally appear?

I will keep the car for a long time since I do not know when I could afford my dream 993TT.
Thanks.

[aigel]

It's tough to predict at what mileage valve guides may let go. 1 quart ever 1500 is pretty good. Once you get to 500 per quart, you'd start planning on new valve guides. Besides consumption, smoke will be obvious (at start up, idle, deceleration) and you will know when to rebuild. At this point, keep monitoring the consumption but don't worry about it.

Cheers, George

[bazar01]

Well, I hope the 500 miles per quart may be a long while. Relief.

What kills the valve guides anyway? Lack of lube, heat, horizontal valve stem wearing on guides faster compared to vertical stems or poor choice of material by Porsche?

[aigel]

I'd say all of the above but heat is probably a huge factor. It just gets a bit more toasty on an air cooled engine. It's a tricky balance to get a valve guide that has enough clearance to let enough oil through for proper lubrication but is tight enough to avoid burning lots of oil. At any rate, todays valve guide materials are superior to what was out there even 10 years ago, so if you ever have to redo the guides, they should last longer than factory.

Good Luck,

George

[aigel]

PS:

Buy Wayne's engine rebuild book. It has a long section about "when is it time to rebuild". It's a good coffee table book until you have to move it to the garage.

George