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Using Synthetic Oil in Flat Tappet Engines
 
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Question:
Using Synthetic Oil in Flat Tappet Engines
I am the original owner of a 1971 Oldsmobile 442 W30. I recently completed a complete frame off restoration. The engine (455 cid) was remanufactured by Jasper Engines in their authentic program. I have heard much hype about the oil to use in flat tappet engines. Jasper recommends a 10W-40 but does not recommend synthetic due to seal leakage. As Mobil™ is an expert in oil technology, I would like to have the benefit of your knowledge for my Oldsmobile. The car will not be raced and is used for recreation only. I drive it about 2000 - 2500 miles a year and never in bad weather. Thanks for your thoughts.
-- Robert E. Walton Sr., Virginia Beach, VA
Answer:
The Mobil 1™ formulation we offer in a 10W-40 viscosity grade is our High Mileage product. Since your engine has just been rebuilt, this may not be the right selection for you. For your Oldsmobile, we would recommend Mobil 1 15W-50. Mobil 1 15W-50 is a higher viscosity oil that delivers a thick oil film for protection of high performance engines. Mobil 1 15W-50 is recommended for older valve trains like the highly loaded flat tappets used in your Oldsmobile. These types of engines may benefit from a higher level of anti-wear normally not required in newer generation vehicles. Mobil 1 oils are fully compatible with all seal materials used in engines.
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