If it states to use premium, I would. The price difference isn't that horribly different that it makes a huge difference. Now if the differnce in premium and regular was a dollar, I might consider it. Would you use dexcool in your radiator when it states mercedes only coolant?

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual