Ask Your Stickiest Question. . . Or ask us something you’ve always wanted to know about using our products. We’ll sort through all the submissions and present the best questions to our automotive experts. We'll share the questions and their answers here.
Switching to Mobil 1 in High-Mileage Cars
I have a 1991 Mercedes-Benz 350SD, and at the 135k-mile service, the dealership switched to 5W-40 synthetic oil. It has been using 15W-40 all along. Recently I purchased a 1995 Volvo 960 with 98k miles on it. I believe the previous owner was using 10W-30. I want to prolong the lives of both cars by using synthetic oil. However, two repair shop people had advised me that synthetic oil is good only if you start using it when the car is relatively new, and that I should not switch to synthetic oil when the car has more than 50k miles. If this is true, what's the reason behind it?
-- Elton Woo, Piscataway, NJ
There is simply no factual basis to this myth. You can switch to Mobil 1™ synthetic motor oil at any age or mileage and, as long as the engine is in good mechanical condition, you should reap all the benefits that you would experience in a new car. In fact, switching a car from mineral oil to Mobil 1 at higher mileage can help reduce engine sludge and other harmful deposits that may have accumulated over the years. That's why highly regarded companies such as Mercedes-Benz and Porsche recommend the use of Mobil 1. One thing you should be aware of it, however, is that your Mercedes diesel and your Volvo may require different viscosities of Mobil 1. Check your vehicle's owner's manuals for more information.