1983 oldsmobile custom cruiser 5.0 v8 307
car looks like [censored] has 390,000 close to 400,000 car was babied most of its life had it since 1990 with 80,000 oil was always changed every 3000 miles or before. oil used was and still is pennzoil 10w40 with a/c oil filter as long as i owned it previous owner had it dealer serviced.. Most of the miles are highway went through 3 transmissions 4 alternators 2 exaust systems 1 carb. axle bearings and a couple of minor front end parts springs and shocks car still drives good a/c has to be charged every summer.
Also for a number of years car was used to haul heavy weight sometimes 400-800 pounds of steel
We have a customer that gets his 99 chevrolet full size van in near showroom condition that has over 340,000 miles serviced here with conoco phillips 5w30 and group 7 oil filter (purolator) still runs good.
Then you have my next door neighbor that has a 2003 mercury grand marquis with just under 200,000 miles and changes his oil here only once a year using our conoco 5w20 and it srtill runs quiet