what weight
TECH Fanatic
Joined: Apr 2005
Posts: 1,231
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From: Just This Side of Damnation
Another thread from BITOG that is very illuminating would be THIS ONE. The key post in that thread is the 12th post, from Dr. Haas.
Probably the most entertaining excerpts from that post are:
"Fully formulated Synthetic SJ 0W-30, 5W-30 and SL 0W-30 oils were compared to SJ and SL 5W-30 mineral based oils for wear. There were no differences. (This is worth repeating - there were no differences in wear rates between mineral and synthetic based oils.)"
Still, synthetics (either real or marketed as) offer some value other than actual wear rates at op temp. It would be up to you to decide whether they are desired in your own scenario and worth the price.
and
"Next are the effects of viscosity and oil temperature. Only ring wear was tested as they state it was most sensitive. They compared basic SJ GF-3 mineral oils. The additive packages were the same. The only difference was the viscosity of the base oils. The following grades resulted: 0W-10, 5W-20, 5W-30, 10W-40. The HTHS for these oils were 2.17, 2.83, 3.09 and 3.76.
There was no difference in wear rates. The oils were tested at all RPMs and Loads, no difference between oil grades were noted. All the oils had increasing wear rates as the load increased but all increased at the same rate across the board."
This would seem to indicate that 0w-10 gave the same warm-engine wear results that were provided by 10w-40. Early in the post it is provided that the most ring and bore wear occur during break-in and the first 20 minutes of warm-up. Would flow be better at cold warm-up than film strength of a heavier but low-flow oil?
And lastly, one for the "I change my oil every 1000 miles." crowd:
"Oil age effects were tested by measuring wear after the oil was subjected to 16,000 miles of city driving. Although the oils thickened some, TAN increased and TBN decreased, there were no differences in wear rates from fresh oil. The test oils were mineral based SJ GF-2."
Probably the most entertaining excerpts from that post are:
"Fully formulated Synthetic SJ 0W-30, 5W-30 and SL 0W-30 oils were compared to SJ and SL 5W-30 mineral based oils for wear. There were no differences. (This is worth repeating - there were no differences in wear rates between mineral and synthetic based oils.)"
Still, synthetics (either real or marketed as) offer some value other than actual wear rates at op temp. It would be up to you to decide whether they are desired in your own scenario and worth the price.
and
"Next are the effects of viscosity and oil temperature. Only ring wear was tested as they state it was most sensitive. They compared basic SJ GF-3 mineral oils. The additive packages were the same. The only difference was the viscosity of the base oils. The following grades resulted: 0W-10, 5W-20, 5W-30, 10W-40. The HTHS for these oils were 2.17, 2.83, 3.09 and 3.76.
There was no difference in wear rates. The oils were tested at all RPMs and Loads, no difference between oil grades were noted. All the oils had increasing wear rates as the load increased but all increased at the same rate across the board."
This would seem to indicate that 0w-10 gave the same warm-engine wear results that were provided by 10w-40. Early in the post it is provided that the most ring and bore wear occur during break-in and the first 20 minutes of warm-up. Would flow be better at cold warm-up than film strength of a heavier but low-flow oil?
And lastly, one for the "I change my oil every 1000 miles." crowd:
"Oil age effects were tested by measuring wear after the oil was subjected to 16,000 miles of city driving. Although the oils thickened some, TAN increased and TBN decreased, there were no differences in wear rates from fresh oil. The test oils were mineral based SJ GF-2."
