Back in the day, Buick engines had a reputation for longevity. Which was saying something when most Chevys and Fords were starting to use oil by 60K miles. 100k out of a Buick that was well maintained was a reasonable expectation. Buicks used a high nickel block which didn't wear as fast. That was with fully leaded gasoline for cheap octane. Putting lead in the fuel makes it dirty. Very dirty. Dirt equals wear. A 2000 mile oil change was standard, 3000 was pushing it. Fast forward to today. Clean unleaded fuel is the major reason engines now typically last 1/4M miles. Oil changes of 15K are now pretty standard. So build your engine with quality valve seals, rings and timing gears and an expectation of a 1/4M mile engine is not unreasonable. With good treatment there's no reason to think it couldn't go even more. Jim
I disagree. The reason engines last longer is not the unleaded fuel per se, it's the feedback fuel injection (cylinder walls aren't washed with gasoline from over-rich carbs, and the choke when cold) and overdrive transmissions (lower RPM at highway cruise.) Unleaded fuel got spark-plug life to 20--30K miles, up from 10--12K. LEAN carb settings--including O2 sensor/mixture control solenoids helped with the fuel wash, which then helped with oil contamination. But the big improvement was the feedback fuel injection. Having precise control over the mixture makes life easier on the bores, the spark plugs, the valves...pretty-much everything in the combustion chamber and cylinder tops. There's something to be said for modern oil formulations--IF (big IF) you have roller lifters or very soft valve springs on your flat-tappet cam. You are unlikely to get 250K of daily-driver use (lots of cold starts) out of an engine that does not have feedback fuel control. If you do, the bores will have considerable taper.
My father in law bought his 68 Buick Skylark 350-2 new in 67. I inherited it two years ago and it had 297,000 miles on an untouched engine except timing chain replacement. Still ran great. I have since gone through the suspension, engine and ST300 2-speed. I love cruising this beauty.
I too think fuel injection has a lot to do with modern longevity due in part to its reliability. A properly maintained carb (rebuilt properly when it becomes leaky, rich and hard to start) is rare on high mileage cars-I think way too many engines that could have gone the distance got neglected in their higher mileage years and that accelerated their decline. My ‘85 Camino had a qjet with the electronic feedback setup; Dad bought it new, drove it regularly, and had it maintained and repaired by the dealer (sought out a carb guy who new them well when it needed help) and it has almost 200k on it and has never been apart. Patrick
