Valvoline is excellent oil but yes, the service rating is the thing to watch. you might try using 1/2 synthetic and 1/2 not. Works really well, enigine will run quieter and burn less oil and it's more friendly to the rubber seals. The only draw back is cranking when it gets down to -30 or so. I think Valvoline still makes a synthetic blend but you can also mix yourself. I just try to to stick to the same brand when mixing.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)