I know I've already stated this but back in the '80s Quaker State was top of the line. Famous engine builder told me he's never taking a motor apart that's been running quicker it's whole life and been dirty. He built me a 500 horsepower engine and told me to run Quaker 20-50 but not racing oil. My friend talked me in to puttingin VR1 in my engine which was totally wrong and also it got dirty both times within 2 weeks. For me I'm going to find real conventional that's got detergent in it ( most commercial is a synthetic blend now) and then I will ad an additive. I'm just going off experience and what I've been reading. I'm no expert or claim to be but I care about my engine.