Quote:
Originally Posted by tjts1
Theres some controversy around that theory. 5w20 oil is popular with a lot of car manufacturers for vehicles sold in the US. Outside of this market they specify higher viscosity oils for the exact same engines in the same cars. They specify 5w20 here because the EPA is pushing them to improve fuel economy via the lubrication system. They're trading off long term wear for a minuscule bump in fuel economy. In a climate like Atlanta, theres no reason why 5w40 would hurt this engine.
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I've heard of that controversy and have done my research. The older modular motors called for 5w30. This was before 5w20 was commonplace. The simple answer is that the motor was designed for thin, 20 weight oil, and thicker oil actually accelerates engine wear in that motor. I've talked to Ford engineers, city fleet managers, and have owned probably 15 Ford modular v8s. I've heard personally of two oil related failures: chain guides worn out after running 15w40 for 50,000 miles and 75k miles - separate cars.