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. Paul On Feb 10, 2008, at 1:39 PM, Joseph Tainter wrote:
> Thanks everyone for the replies to my question about 5W-30 oil. Now I > understand. > > A couple of you sent replies like this one from Paul: > > "At one time powerplant experts thought that wider bearing clearances > and heavier oil offered optimum protection. Eventually they discovered > that lighter oils and tighter clearances resulted in less wear, better > power and better fuel economy. What's more the 10W-40 oils sometimes > caused sticking of rings under some conditions. Not good." > > Does anyone know when this change in engine design took place? > > My 1989 Volvo 740 has 230,000 mi./370,000 km. and burns no oil. I have > been using Castrol synthetic 10W-40 oil in it year round. Should I > switch to 5W-30 or continue with the heavier oil? > > My wife was advised to use 20W-50 in her 1967 Austin-Healey Sprite. > Should she change to something lighter? > > Thanks again, > > Joe > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > 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 PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
