97 mustang

You didn't specify your engine size. But, I'd check your owner manual to see whats recommended for your engine. If you don't have your owner manual, look in the engine compartment for a sticker that specifies. Sometimes its on the oil filler cap or the dipstick too. If you can't find anything, you'd probably be safe to stick with 10-30. Especially if its a V-8 thats not burning more than 1 quart between oil changes. If your using synthetic already, stay with synthetic. On the other hand, I've heard that switching from conventional to synthetic is not a good idea on high mileage engines. Hope that helps.

Mobil has a procedure for doing the fossil-to-synthetic switch.

I'd guess they were sincere, and not just trying to sell a few more quarts of Mobil 1.

Valvoline has something to say, also.

Amsoil rings in.

PennZoil.

Gooooogle offers about 149,000 articles on "switching from conventional to synthetic oil".

>

>

The oil on the dipstick on that page looks almost as good as mine does.