Date: Tue, 05 Jan 1999 09:11:42 -0500 From: Ron Vopicka <cvopickanopsams.com> Subject: Re: Any 300K miles engine around? Need real data...
> Not true, a lack of oil changes can cause build up around the rings. > Eventually the rings become seized into the grooves and you suffer from blow > by. Blow by effectively blows out the spark, causing poor fuel burn and > higher tail pipe emissions. > Better put, a lack of oil changes at the proper interval. A big part of "wasted" oil in my view is the excessive changing of oil during the first 100-200k miles. As I have mentioned before, I am a 10k mile change freak (or twice a year, whichever comes first). At 270k miles on one engine now, I am changing the oil every 7500 (but since my car usage has decreased with retirement, it is still twice a year). The first oil change is quite important, especially if the mfg isn't particularly careful about cleaning casting material, metal shavings, and abrasive grit from their new parts before assembly. After that a well-designed, good, tight engine should suffer almost no additional damage with more extended periods between oil changes. As the engine starts to wear (a natural process, even if you change your oil every 1k miles), the change interval time should be decreased in order to get rid of increased amounts of foreign particles from blow-by etc. (None of these comments apply in EXTREME service conditions). > > FWIW, most 5 litre GM V8's use 5 qts of oil. A BMW V8 uses 8 qts. The > added oil volume increases it's cooling and cleaning abiliity. There should > be no reason for an Alusil BMW V8 to not run in excess of 300k miles. And a (for instance) 270k mile 1986 Camry uses 4 quarts. Under most conditions the added oil volume is a detriment. Unless you are driving a minimum of 30 miles at a stretch, never in subfreezing weather... your oil will never warm up fully enough to boil off the water that gets into it from the combustion process. The oil is diluted by both gas and water vapor. If the oil does not get up to temperature and STAY there for a while, these contaminants stay in the sump... and get circulated all over the internals of the engine. A case in point. 1967 Porsche that took 9 qts of oil as I recall. Driven in Florida (so subfreezing hardly ever applied) and driven a minimum of 10-15 miles on each trip... After driving that way for several months, I would take a 1500 mile trip to NJ, and in the first 400 miles of driving the oil level would go down 1 to 1.5 quarts. After that it would return to its usual 1200 mile per quart consumption. I don't think that was all oil that "burned" in the first 400 miles. Now is 6, 8, 9 quarts good if you are driving LeMans... absolutely. You get the oil good and hot, it stays up at a temperature for good lubrication and higher engine power output and there is lots of room for the additional contaminants that come from extended high specific outputs over long periods of time. But for a typical ownen/driver, no. Ron
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