I don't care what car it is, I will never go 12k miles on an oil change, period and that's probably because there's an American mentality to change your oil and filter every 3k miles.
My 88 M5 has had, for the past 197,000 miles Mobil 1 synthetic every 3k miles. Every 10k miles I check the valve adjustment (it calls for 15k intervals).
I have, in 30k miles, changed 2 shims out. That's it. And when you adjust the valves the valve cover comes off, and the inside of my engine SHINES, it's as clean as a 30k mile one I worked on. Not too long ago I had an oil analysis done, no metal in the oil. Oil pressure is on spec with a new engine, it burns hardly any oil, and the only work the engine has ever had done to it is a new timing chain and tensioners strictly as a precaution (The US-Spec M engines had double row chains and aren't prone to failure like the Euro-spec M88s). Oh, original spec was 256hp at the crank, the car, with the cat removed, a chip and, umm, that's about it puts out 240 rear wheel horsepower. If it helps, the car has done close to 100 track days in its' life. It's an old M car, so it doesn't develop decent power till it hits 5 grand and it sees full throttle shifts at 7 grand all the time, I "drive it like I stole it".
Granted oil is much cheaper here, but even so.. a proper rebuild on an S38 is $7,000+. Even at £5 per quart/litre it's still cheap insurance.
My modern cars (Lexus GS350 and Jag XJ8) get oil and filter changes every 4k miles, sometimes the Lexus goes to 5k but that's it.
As far as oil goes... well, Wal-Mart synthetic used to be repackaged Pennzoil Q, which is factory fill in Ferraris
Before they switched I stocked up on the stuff
) dipstick, after about 2K miles.
