Back in the day I had a 1969 BMW and it would leave a smoke trail on decelaration. Turns out the Castrol GTX I was using was a contributing factor. Upon the recommendation of Hardy & Beck (I lived in the neighborhood at the time) I switched to Valvoline and the smoke virtually disappeared. I'm no oil engineer but I do know what I can see in my rear view mirror!!!
I miss the days before they became yuppie icons......
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