My 87 Cougar has 350,000 miles on it. It uses mabe a qt. between changes at 3,000.
I use an oil additive that really works. Go get a dictionary and look up Molybdenum Disulfide. Now, go on the web and search for this and try MrMoly. I am surprised that very few people know about this stuff. If you have really good tools they probably say "Chrome Moly Steel" on them. That is because when the steel was smelted Moly was incorporated into the mix. Look, the engine will last almost forever, runs a bit cooler, is noticeably faster, is quieter, uses less fuel. I am getting 28 to 32 mpg on the highway at 70 and 80 MPH. Last run to Toronto (Canada) from my home we averaged 26.8 MPH, and that included about 20 minutes of driving downtown Toronto. Anyway, go look up everthing you can find about Moly. Be careful using some of the artificially made additives. Some crystalize, shale off and score the guts of your precious motor, and you loose about 6 psi oil pressure. I have a '71 Stang and it has a 165,000 miles on it, it sill runs very strong, uses very little oil, and absolutely nothing has been done to the engine other that change ONE valve cover gasket. I can pull 55 mph in first, 93 in second and I have not the courage to find out the rest, but can attest that it will go 130 mph. We pulled a 4000 lb house trailer with it, ran the car pretty hard and still the compression is up and it runs fine. Not bad for a 2bbl 302 Windsor engine. Oh yeah, I have dusted off 350 Cameros and Firebirds. Big shock to there owners. I do have a Haynes tranny cooler. That is it.