Myth: Mobil 1 will leak out of the seals of older cars.
Reality:
Mobil 1 does not cause leaks. In fact, Mobil 1 was tested in dozens of industry-standard and OEM tests to prove its performance. It is fully compatible with the elastomeric seals and gaskets used in virtually all modern engines.
When the first Mobil 1 was introduced 30 years ago during the energy crisis, it was a very low viscosity grade (5W-20) that was optimized for fuel economy. At that time, engines were designed for much heavier grades of oil (e.g., 10W-40) and tolerances were much “looser” than in today’s engines. Sometimes, the original Mobil 1 formula used in an older engine would actually clean out the sludge build-up that was keeping the oil from leaking. Engine designs produced since the mid-1970s are made with tighter tolerances and better seals, and the phenomenon has disappeared.
Likewise, in an older engine in good condition – one that does not have oil leaks or one that has been rebuilt properly using new oil seals – Mobil 1 provides the same advantages as when used in a new engine. If an older engine has an oil leak, ExxonMobil recommends repairing the leak, then using Mobil 1.