968norway

Hi, when I bought my car 2 years ago it had 182,000 km on it. The motor had been rebuilt at 171,000 km, so that seemed good. During the last year the car has been using increasing amounts of oil, to the point that this last week it used almost 3/4's of a liter for 750 km, quite a bit. The car is now at 203,000 km, no obvious leaks or smoke, could it be the valve guides? If they were ok when then engine was done, it is not likely they would have changed them.
Cheers,
Tore

Mondrian

Was it a proper rebuild or just a reseal? At that sort of mileage valve guides should have been replaced.

968norway

As far as I know it was a proper rebuild, piston rings, heads, head bolts and such, it was the previous owner who had it done. I have to dig up the paperwork and see if it mentions valve guides, though they may not be specified. The first year I had it, it used very little oil.
Though back to the question, if everything else is ok, the valve guides would the most likely suspect?

Steve Weiner-Rennsport Systems

I would pull the lower valve covers and measure the side-play in the valve spring assemblies. If its excessive, it sounds like the guides need replacement.

The other thing is performing a leakdown test to make sure there are no ring sealing issues.

968norway

Ok, thanks. I would hope the rings are ok since they are only 30,000 km old, but you never know.

Earlydays

My understanding is that Porsche considers an oil consumption of 1 liter per 1000 km. to be not abnormal....

968norway

That is correct, but I have tended to see it as a limit, sort of 'up to'. I may have exceeded that last week. As it is, I have the car booked in next week to have it checked out. One of the reasons I bought it was the rebuilt engine, thought it would be ok, this is a rather disappointing development.

Saab96

What kind of oil do you use? My oil consumption dropped drastically after I switch to 10w-60 oil. Used earlier 5w 40 oil and the consumption was 0.5 liters per 1,000 kilometers, now the consumption is less than 0.5 liters on 2,000 kilometers, which is quite ok. I also fixed some small oil leaks on the engine.

968norway

Oddly I just switched from mobil 1 5w-50 to classic 10w-60 last week, though the increasing oil usage thing had started before that. It might have something to do with it though.

LM964

"Approx. 1.5 liters per 1000km (1.6 US qt per 621 miles)" is the Technical Data reference.

140k miles and I'm using less oil than the factory allowance above, so quite happy. Swapping over to 10W-50 from a 40 has also seemed to have reduced consumption further (even after 3 days of tarmac rallying)!

bweSteve

I switched from M1 20w-50 to the Classic 10w-60 earlier in the summer...

And I am currently noticing a significant drop in oil consumption AND a lot less smoke puff upon initial startup (esp after it has been sitting for weeks).

Personally my opinion is that the formula Porsche has used for the Classic has better degree of Film Strength, and thus less leakage across the rings or past the guides.

People have stated that they think the Classic has a lower degree of Phosphorous & Zinc (compared to the M1 20w-50 V-Twin),... but I am not convinced that those highest %'s are absolutely the golden rule for choosing your oil.

Time will tell. I plan to send my oil samples to Blackstone after my next oil change for analysis.

Plus,.. for me,.. my Parts Mgr at P dealership met the same price for the M1 20w-50 (that I could get off Amazon). Hence I made the choice to switch & try the Classic.

Oh, and I just posted this under another thread too,... but might as well post the link here too,... in case any of you want some light reading of same discussion...
https://rennlist.com/forums/964-turb...-this-oil.html

=Steve

wallra

I also switched my oil to total and my oil consumption went down plus is has a high zinc content. I did'nt want to use synthetic because the engine never had it. It's 20w-50.

Steve Weiner-Rennsport Systems

Hi,

Based on some experience, I can tell you with confidence that the air-cooled engines need 1200 ppm of ZDDP. Anything less than that usually results in camshaft & rocker arm damage.

I would not use any oil that you haven't performed a VOA or have found reliable test data to that effect.

Remember, its YOUR engine and you will shoulder the costs.

bweSteve

Thanks Steve. Agreed.

I was referring to post # 10 in the thread pointer I listed above, where it was stated the following numbers:

"Mobil 1 20w-50 v-twin contains 1600 ppm and 1750 ppm, P and Zn, respectively. Mobil 1 15w-50 contains 1200 ppm and 1300 ppm, P and Zn, respectively."

And other folks have said they "think" Porsche Classic 10w-60 has less than 1600 P & 1750 Zn. How much less?? No one seems to know (until someone sends their samples off for testing).
Would be nice to know though. You are right, clearly I am going on blind faith that Porsche has put enough Zn & P in their special sauce (because they do not publish those #'s).

It IS my engine & I LOVE it.
=Steve

Mondrian

OP - do you have standard intakes or performance intake such as K&N / cut filter box & lightweight filter? Reason I ask is cause I think such products while enhancing power would accelerate engine wear & tear by allowing more/bigger particles in the engine. Hope SteveW would chime in on this.