[aerohead]

1) I visited motor oils the other day.
2) Cars that MotorSilk marketed to were using API SD oils.
3) Today, we're up to API SP oils, with viscosity as low as 0W-8 ( Mobil I, 100% Synthetic, designed for hybrid cars requiring SAE 0W- 8)
4) Mobil Corporation is recommending the oil & filter change @ 10,000-miles.
5) A 20,000-km oil & filter change interval exceeds Mobil Corporation's interval by 24%, and we're talking about a motor oil approved in 'supercars.'
6) I may be wrong about the 'discoloration', but I'll ask local dealerships for samples of warranty car oil drained @ 10,000-miles to have a 'look' ( I've never seen used motor that wasn't discolored, in 68-years ).