Date: Thu, 13 Feb 2003 17:37:58 GMT From: Paul Halliday <pjghnopsamyonder.co.uk> Subject: Re: use fossil or synthetic oil?
in article b2g7ti$1c2qce$1nopsam52899.news.dfncis.de, Grunff at grunffnopsam.com wrote on 13/02/2003 13:50: > Paul Halliday wrote: > >> On older cars where the oil >> used by previous owners is not known, there is a risk that synthetic oil >> will clean away mineral deposits and slight leaks may occur, but I've been >> lucky. > > "Slight risk"? "Slight leaks"?? Paul, I suggest you've been > *very* lucky. > > While I'm in no way disputing the fact that synth is very good, > and especially appropriate to turbos, there is a real, big > danger of *major* oil leaks when switching from mineral to synth > at higher mileages. > > I've personally experienced this twice, and seen it happen to > others many times. I think the main mechanism is seal shrinkage > (mineral oil swells seals quite a lot, which compensates for > seal wear, whereas synth doesn't). > > Unless you're happy to change your front and rear crank seals, > and probably your oil pump o ring, then don't change from > mineral to synth at high mileage. I have been lucky, phew :) I was prepared for the crank seal replacements, and do the first oil changes prior to it going to my garage for a "good going over" - there are always a few niggles when you buy a car. My first turbo died of other problems at around 157,000 miles. The injection is now at 150,000 miles (45,000 plus mine) and still going strong. Orca has been on various synthetic oils for some years prior to my ownership. Paul 1985 900i 16V 1989 900 Turbo S http://pjgh.go.dyndns.org/saab/index.html