mls@husky.uucp (Mark Stevans) (11/16/85)
According to my 1984 Toyota owner's manual, 10W-40 should be used for ambient temperatures above 40 Farenheit. However, my Toyota dealer says that 10W-40 has fallen out of favor with manufacturers. It seems that various polymers are mixed into 10W oil to "stretch" it to a 10W-40 multigrade are not quite stable enough, and break down too quickly in high temperatures. 10W-30 is about at the safe "stretch" limit, and so it is recommended instead. This seems to make sense to me, but might not a less polymerized oil, such as 15W-40, be better than the lighter oil, at least in the summer? Mark Stevans ritcv!husky!mls