My brother-in-law has a 91 full-size Chevy Caprice with a 305 engine. This vehicle was starved for oil changes by the previous owner. I found this out a couple years ago when changing the valve cover gaskets and found each side full of gunk. I cleaned it out best I could and opened up the clogged drainback holes, etc. This stopped his oil leaks. Now, 60k miles later his vehicle is leaking about a quart every 500 miles or less, mostly from the front and rear main seals. He does not have money to replace this engine or do major repairs. The engine now has 190k on it and he drives about 800 miles a week back and forth to work. Amazingly, he gets consistently 24+ mpg and this vehicle runs great. The vehicle calls for 5w30 oil. I told him to run some Advanced Auto SAE40 $.99 oil in the hot summer heat, and we will just swap out the filter every 5000 miles (all highway). Then in the fall we can change the oil out to an inexpensive 10w30 or a little more pricey 15w40 and continue swapping filters until spring. We are in South Carolina, and he's diving to the other side of Charlottle, NC daily, for now. Well he took my advice, and it seems the leaks have slowed some. I don't think the engine consumes much, because I never see any blue smoke. He says his fuel mileage is still great,too. Am I on the right track with what I told him? I swear this car seems indestructible- has original 700R4 trans. and the AC is cold, too!