Mobil1 0W40 is relativly new and your manual is old. I'm not saying that it should be used in you model of car, but you need to understand that the 0 number is the weight when the oil is cold, once your car starts warming up it is a 40W oil. Again the 40 is the important number. The O when cold allows for fast oil pumping upon start up. 0w40 will protect your car as well as 10W40.. I believe this is in the newer cars and listed as a viable synthetic oil weight for a 91 300E by Mobil1. Meets MB standards.