I have a '95 Cadillac Seville SLS. I have driven Caddies for the last 20 years, and have always used Mobil 1 in them. It seems that eventually all of them have developed oil leaks.
Recently a mechanic told me that Mobil 1 is too "slippery", and that is what causes the leaks. Is this true? If so, I can save a heck of a lot of money by just using good regular oil.
The mechanic giving you the "slippery" theory on oil leaks might be a little off the mark. Synthetic motor oil isn't going to leak any faster than conventional. The problem is the lack of quality engineering by American car manufacturers over the years. That's where the spots on your driveway are coming from.
The big advantage to Mobil 1 is its ability to maintain viscosity under extreme temperatures, much better than conventional motor oil. So if you're in an arctic climate area, or Death Valley, it may be worth the cost. Otherwise, you're right; you can be saving money with quality petroleum based motor oil.