I have used Delo 15-40 in my 86 560 SEL(sold at 200K miles) and 1991 300SE (sold at 145K miles) with great results. Good cold (for Oregon) starts. Don Rasmussen MBZ which bills itself as the oldest MBZ USA dealership, used (in the old days before synthetic) Pen 15-40 long distant for all its oil changes both gas and oil burners. This is a similar formation as Delo but in many opinions, not quite as good quality (subjective). Just change it every 3,000 mlles.