Started using Mobil 1 on both my (98 F-150 & 97 Saturn S-series) vehicles at about 95,000 miles each. Previously had done 3,000 mile changes with Penn 10w-30.
Neither leaked any oil before or after the M1. However, the Saturn consumed about a quart every 3,000. The F-150 has never consumed more than a few ounces of any oil even at 6,000 mile change intervals with M1.
No problems no leaks and they now have 135,000 and 126,000 respectively.
One benefit to the M1 was the Saturns oil consumption dropped to about a quart in 6,000 miles.
Neutra treatment and Schaeffer's 7000 15w-40 has dropped the Saturns consumption to 4oz. in the first 3,000 since switching to the Schaeffers.