i was looking at havoline synthetic. on the oil charts bob has here, it looks wonderful!! i was comapring it to mobile 1 synthetic on paper, and it seems the havoline outperforms! i wonder why it hasnt caught on?i have a 1995 plymouth neon, SOHC. veyr hard drivin, stop and go traffic, even on the highway here. my car has a rear main oil leak. synthetic is coming out a little faster than with regualr oil. i was looking at valvolin hihg mileage synthetic. that any good? i was thinking of using a good stop leak additive with the havoline synthetic, thats why i ask about it as well.