Simply look at your owner's manual for which weight oil is to be used for expected temps. My nieghbor has a '91 Audi 100 and it calls for 15W-40 or 15W-50. I don't think there is an oil sold that has a rating less than SJ, including Delo 15W-40. One of the things I have noticed written on the back of heavy weight oils, is the words "provides superior protection". I don't find this on lesser weight oils like 10W-30 or 5W-30. Just a little interesting fact, one of those "Hmmmmmmmm" things.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member