Not to start a lubrication war thread here but the usage of mineral
versus synthetic and the proper weight oil for the application is a
subject of debate. FWIW, I've got 800 miles on a complete rebuild and
am still using mineral based oil. I started using 10W/40 for the first
750 miles and changed it over to 20W/50 last weekend. The weather here
in Maryland has not been overly hot of late and on days with 80F temps,
I had 70lbs at 2000 rpm and 45lbs at idle. Since changing to 20W/50,
the top end stays the same and the idle pressure is up just a tad. I'm
not convinced that the heaver oil in a tight engine is necessarily a
good thing. What the engine needs is lubrication flow and my numbers
indicate that 10W/40 is just fine.
Additionally, I'm not convinced that I want to go to synthetic for this
car as I only expect to put 2000 - 3000 miles on it each year. They
were designed in the days of mineral oil and have operated many years on
it just fine. From a cost standpoint, it might not make sense as I'll
still probably change it every season and spin on a new filter anyway.
I DO recommend synthetic in daily drivers and have been using it for
several years in my '91 Honda and '97 Caravan without any problem,
stretching the OEM recommended interval to 8 - 10,000 miles on each.
Out of courisity, I've checked what my original owner's manual on page
66 states wrt weight as af function of ambient temperature and have
included it here:
Temp Range SAE Viscosity
Above 14F 10W/50; 20W/50
10W40; 20W/40
-5F to 50F 10W/30; 10W/40; 10W50
Below 14F 5W/20; 5W/30
Just my opinion, folks. Happy Motoring and hope to see some of the East
Coast folks at Bowie tomorrow.
Gary
Digest '75 TR6
Severn, MD
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