I tried searching, but your search returns off the wall results for threads that I know exist around here, so I apologize for asking a question that has probably been heard a million times. My 1993 850 with 260K miles on it has leaky valve stem seals (common on whiteblocks). I'm losing about a quart every 1000 miles. It is currently due for a service and I was thinking about giving the Synthetic Oil Stabilizer from Lucas Oils a try; but that seems to be a HUGE no-no on this forum. My other idea was to switch from Mobil1 0w40 to Mobil1 high mileage 10w40. I don't like that because it seems a bit thick when cold, but if it helps, I am definitely open to the option. What do you suggest? Also, I would prefer to stick with Mobil1 as a brand, no other oils please.