I changed over from Havoline 10-30wt at 118,000 miles. at that time the rear main seal would drip once when parked, but the bottom of the engine and transmission stayed dry if I cleaned them before a test drive.

I figured that small oil loss wasn't much to worry about until the next rebuild.

I've been running Mobile 1 for about a year now - two oil changes - and I haven't seen any increase in leakage or burning of oil.

When I adjusted the valves several times before the changeover I did notice that there was no sludge or discoloring of the inside of the rocker cover or the top of the head. That should mean that the PO did her oil changes on a regular basis - at $185.00 per change!

I think if you have significant oil loss from the front main seal, the best thing to do is to fix it now, rather than try to go back to dino oil in hopes that it will cure itself.

The front seal is a fairly easy job, requiring that you pull the radiator, fan, front pulleys, and timing cover. You could probably do it in one afternoon, two at the most.

The only 'special' tool you'd need would be a torque wrench, which you can usually rent at an auto parts store or even some home centers.