I dont switch back and forth, I have used 'Dino=Regular oil' like 2 times. Thats when Chevy changed it for me, and they told me it doesnt matter if you go back and forth....but I prefer 100% Synthetic, the Castrol blend was good, and a decent price, but now it is nearly the same price as total Synthetic. So I use that. I never loose oil, not a drop, I dont burn any oil, I have said it here that I hear guys saying they 'only' loose a quart of oil between changes, and they are thrilled, I would be in a panic! In all the cars and trucks I have owned, I have never lost a drop of oil,ever. But then again, I always buy new and have always traded in at 3 years, BUT this one is staying till it is to expensive to fix. No car payments is kind of nice.