5W20 or 5W30 Another Ford question

BlueOvalFitter

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I use 5w-20 in my Ford as recommended. I would trust Ford engineers over the advice of your mechanic.
Ford recommends 5W20 for my 4.2 V6 engine.
When the Ford 4.2 V6 engine first came out in 1997 it was spec'd 5W30 up until 2000. From 2000-2008 (2008 was its last year) Ford spec'd 5W20 and back spec'd 5W20, ONLY for CAFE reasons. BUT, from 1997-2008 the clearances and tolerances inside the engine NEVER changed!
So, I use what Ford recommends; 5W20 when I find it on sale or mostly 5W30 because I can, as well as Ford.
WHY 5W30? Again, the internal tolerances and clearances NEVER changed the whole time this engine was manufactured. :cool:
 
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There is not a lot of difference between a 5w20 and 5w30 but I'd still use 5w30. You get below about 2.9 HTHS and the oil starts to depend more heavily on additives to perform.

We tow with ours so it gets a thin 5w40. I've got enough QS Euro 5w40 stashed to get it to about 120k.
 
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I use 5w-20 in my Ford as recommended. I would trust Ford engineers over the advice of your mechanic.
Ford engineers didn't dictate the oil viscosity, CAFE did to make sure they met MPG guidelines... which has NOTHING to do with engine longevity or reliability.
 
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Just think, all those Crown Vics that made it to 400,000 miles as cop cars and later on as taxis running 5W20 bulk oil could have made it to the moon and back if they used synthetic 5W30.
 
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Just think, all those Crown Vics that made it to 400,000 miles as cop cars and later on as taxis running 5W20 bulk oil could have made it to the moon and back if they used synthetic 5W30.
Cop cars and taxis are a different realm... they stay running 90% of the time which has a detrimental effect on the engine reliability.
 
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Just think, all those Crown Vics that made it to 400,000 miles as cop cars and later on as taxis running 5W20 bulk oil could have made it to the moon and back if they used synthetic 5W30.

A lot of those fleets of Crown Vics used 15w-40 and did make it to the moon and back. Lots of idling results in more shearing
and fuel contaminating the oil.
 

CJL

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Interesting article from Machinery Lubrication:

 
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