Question:
Switching From Conventional Motor Oil to Mobil 1
There seems to be confusion about how to make the switch from conventional motor to synthetic. I am a do-it-yourselfer. Could you provide instructions?
-- Joe D., Miami, FL
Answer:
The instructions are very easy to follow: Simply change the oil as you would normally. Any “confusion” is just myth. You can switch from conventional motor oil to Mobil 1 synthetic (and back again, if you want), without following any special procedures. The only exception to this is with a higher-mileage engine that has never used synthetic motor oil, or with an engine that has used conventional motor oil and been poorly maintained. In these cases, you should still follow the same basic oil-change procedures (drain the old oil, remove the old oil filter, put in new Mobil 1 and put on a new oil filter), but you should follow a regimen of one or two shortened oil-change intervals. For instance, let’s say that your regular oil change interval is 5,000 miles. If you’re switching to Mobil 1 under the circumstances mentioned above, make your next Mobil 1 oil change in 2,500 miles, your third Mobil 1 oil change 3,500 miles after that, and then follow your normal 5,000 mile oil-change interval. The reasoning behind this staggered interval is that a high-mileage engine, or one that has seen infrequent oil changes, will likely have a considerable build-up of sludge and deposits. Mobil 1 will help clean the engine as you drive, but it will have to work much harder in a very “dirty” engine, and so it is best to change the oil more frequently for those first few thousand miles. After that, you can rest assured that Mobil 1 is continuing to keep your engine running clean and well lubricated for mile after mile.

Question:
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
Answer:
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.