A temperature spike is never good.
Many years ago I ran 0w-30 oil in my camaro for a long time then one summer I switched to 10w-40 and saw a 10 to 15 degree temperature reduction and have ran 5w and 10w-40 ever since.
I agree, I would not run 5W-20 in anything higher milage even if speced for that oil.
Remember manufacturers recommend 0w-20 or 5w-20 for their benefit, not yours.
Cummins did a fuel economy test on their engines and found that there was only a 3% fuel economy difference between 15w-40 oil and 5w-20 oil. And only a 1% difference between 10w-30 and 5w-20 oils.
I posted a link to that study on here some where on another oil question post.
__________________
1984 chevy suburban, custom made 6.5L diesel turbocharged with a Garrett T76 and Holset HE351VE, 22:1 compression 13psi of intercooled boost.
1989 firebird mostly stock. Aside from the 6-speed manual trans, corvette gen 5 front brakes, 1LE drive shaft, 4th Gen disc brake fbody rear end.
2011 leaf SL, white, portable 240v CHAdeMO, trailer hitch, new batt as of 2014.
|