A k20 unless its a k20a3, which I cannot speak for, is going to knock on regular gas... Just go ahead and be safe and put Premium in it anyways... You pay what $2-$3 more per tank if even that? But if you add in the extra MPG you will get it comes out to less that that. So yeah... be nice to your car and spoil it in gas It couldn't hurt and the benefits out weight the negatives.