Besides better low temperature properties (lower pour point) due to absence of wax, synthetic hydrocarbon oils (poly alpha olefins i.e. from C2 to C10 to branched C30 or 40) have better oxidation stability than refined mineral oils. This will benefit high temperature operation as for example running at high speed at German autobahns. There are also semi-synthetic oils which are derived from cracking hydrocarbon waxes; these have a lower price tag as synthetic oils and have intermediate properties.
Henk > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of William Robb > Sent: 10 February, 2008 10:17 PM > To: Pentax-Discuss Mail List > Subject: Re: Follow-Up OT: Question for Pentax Auto Buffs > Discussion Group > > > > ----- Original Message ----- > From: "Paul Stenquist" > Subject: Re: Follow-Up OT: Question for Pentax Auto Buffs > Discussion Group > > > >I think the 10W/40 is a good choice for the Volvo. Remember that > >clearances open up as the engine wears. That oil is probably a bit > >heavy for the Sprite if it doesn't have a lot of miles. I'd use the > >10-40 synthetic in that as well. I use 5w-30 Mobil 1 > synthetic in my > >55 Chevy, but the engine was rebuilt 20,000 miles ago with > >contemporary bearing, valve guide and piston skirt clearance. > > As an addition to this discussion, I was told by my cousin > the petrochemical > engineer (he headed up the design team for Royal Dutch Shell > that created > unleaded gasoline, and then later CFC free styrofoam, of all > things), that > from a user point of view, the difference between > conventional motor oil and > synthetic is that conventional oil, no matter how well > refined, has waxes in > them which coat the bearing surfaces when cold and impair > lubrication out > until it melts back into the oil. Synthetic oil, being > sourced from natural > gas, doesn't have this problem. I suspect that if you live in a warm > climate, synthetic oil is rather a waste of money, since it > will never be > cold enough to harden out these waxes. > > William Robb > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly > above and follow the directions. > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
