I Am Tired of Hearing About the 3k Mile Oil Change

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AEHaas,

Depends on specifics.

I do 3000 mile OCI on a Porsche 911 with 176K miles on it.

Why ? Castrol GTX 20W50 usually cost me $1-1.50. 12 qt capacity so thats $12-18 + filter. It consumes 2 qt's in 2000 miles (that's better than most 911's ~600mi/qt). Usage accelerates as oil gets dirty in this thing. It would probably consume 5-6 qt during a 5000 mile OCI. It does not make sense to to me to keep adding new oil to the old. Consumption is due to brass valve guides on this application.

Next I don't want to price out a rebuilt engine. I'll guess maybe $10K installed. Ok, maybe I can get just heads rebuilt, $4K. That buys a lot of oil !

Finally I believe the consumption accelerates with GTX due to sheer down and ZDDP depletion. I don't really know. The engine sounds better with fresh oil when swapping out GTX.

BTW, during the first 120K I did 7.5K OCI figuring the 12 qt capacity would help (Porsche recommends 15K OCI). At 17K miles it consumed 2qt/3500 miles. I now know that was too long as oil consumption increased.

At 3000 mile OCI over the last 55K miles consumption has been stable. That's why I do 3000 mile OCI, I wish I had done this from day one....
 
"What about car manufacturers whose "severe service" recommendation is approximately 3k miles/3 months? I would venture to say that the vast majority who keep cars in an urban setting qualify for "severe service", so would you recommend owners of those cars to disregard what the manufacturer says?"

No. If they use Joey Chumlo's oil.
Yes. If they use a quality oil.
 
No offense to Doc Haas, but in my case, and most of the folks here, or at least for a like situation (rollerized DOHC 4 or 6 cylinder, drive 3-5K/ month average performance), 5W20 SM/GF4, 5000 miles a month, a 7500 to 10K OCI on syn, 5-7.5K OCI on dino is perfectly reasonable.

If I was driving the beastly vehicles the good Doc is, I'd change more often, but for a 106HP Hyundai driven mostly interstate/parkway, never in stop and go? Taint worth the trouble or the oil. Show me a high wear number or low TAN/TBN at even 10K on one of these, I'll change more often.

Till then....
 
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