Switching between Engine Oils Synthetic and Regular?

I dont have any evidence to point you to, but you should NEVER EVER MIX regular dino oil and synthetic. I also highly recommend AGAINST switching oils. Either stay with regular oil or stay with synthetic.

Why?

To the original poster... mix the oils that you regularly mix in a clear glass, and watch to see if they separate or do anything else funky. If they don't, you shouldn't have any trouble mixing them in your car.

I stick to one brand of oil, but I really don't see any reason why switching (assuming you're using the correct grade/viscosity/etc.) would cause any problems. If there's a reason (other than myth) that I'm wrong, I would like to know.

Craig

All synthetic oils I've ever used explicitly state on the label that they are 100% compatible with regular oils, and there's no worries at all about mixing them. You will compromise the qualities of the synthetic by doing so, but it won't do any harm. I've done exactly what you've described, many times, and I've never had any problem.

Check your oil's labels.

I've been switching back and forth for years (>20) in multiple brands of cars and have never had any engine problems. When synthetic oils first came out (and everyone was hesitant to use them) I read a suggestion in a book on extending engine life that recommended adding one quart of synthetic with every oil change to get some of the benefits. Now Valvoline makes a product named Durablend which is exactly that, synthetic and dino oil mixed together. So I'd say you are fine.

HTH Steve

With a comment like that you may be banned from here and doing oil changes. As for my 2 cents... as the name implies "synthetic oil" is man made oil. Don't worry, be HAPPY!

Thanks for the peace of mind!

Now is it OK to mix Dr. Pepper and Rum - no - hang over and horrible sugar rush.

Tmuld.

I haven't been around here long enough to catch your innuendo, Woodchuck. What do you mean?

For me, the synthetic oil would taste better than DR.Pepper.

Jim B.