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why not 10-40, you have light oil when its cold and heavier if you need it when its hot, best of both worlds
in response to another comment never heard of an engine failure running 10-40
That is not how it works. The second number is the viscosity when the engine is at operating temperature. Running a 40 weight oil in a car designed to use a 20 weight oil will most likely give you problems. Not right away but a true 40 weight oil is too thick for the 4.6 IMO.
Running M1 5W-30 is fine because lab tests show that the Mobil 5W-30 is closer to a 20 weight at temperature. I'm not an oil expert but I did read a lot over at bobistheoilguy.com
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I personally would drain and put the correct oil in there. Just leave the Filter. The 5w20 will dilute down the 5w30 sufficiently that the motor won't know a difference.
Better safe than sorry IMO...just run the spec'd stuff.
Quote:
Originally Posted by Riptide
I've never read or heard of a single engine failure due to using a 20 viscosity oil.
x2
been using the 5w20 in my Fords for about 10 yrs now. From 100% stock motors to Supercharged 5.4 3v that I drove extremely hard.
never once had an issue or any noise. From Washington to Texas and now Hawaii.
Ford Engineers spec'd it for the CAFE requirements...yes. But the engines are also built with this oil in mind. A thicker oil isn't necessarily going to lubricate the same areas as well as the 20 wieght can/will.
They are the Engineers who have intimate knowledge of these motors...not us. I recommend you stick with the Experts. Heck, even Roush/Saleen say to use the 5w20 oil. I think they'd recommend a different viscosity if it was a problem.
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I called one of the two (can't recall which) and was told a 30. I can't remember where but I think I found it on both websites. Was a while back when I looked though.
I called one of the two (can't recall which) and was told a 30. I can't remember where but I think I found it on both websites. Was a while back when I looked though.
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