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Discussion Starter · #1 ·
Yes, I know this has been discussed... But I cannot find a lot of recent threads.

Does anyone have long-term experience with 5W-20?

For context, my '97 3.8 calls for 5W-30 per the owner's manual. In 2001, Ford changed that recommendation retroactively to 5W-20.

Here is a TSB to that effect:

My car has about 43.000 miles on it, and I've owned it for four months. I have no idea what oil the previous owner used.
 

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There is a lot that goes into deciding what weight oil is recommended for what engine, but generally speaking thinner oils are being specified for gas mileage, not for engine longevity. Too thick of an oil can also be bad as it limits the ability of the oil to flow, and also puts more strain on the pump, so don鈥檛 go putting 15w40 in there either. My opinion is to use the oil that was specified for the engine when it was originally designed. The oil pump, bearing clearances, oil galleys, and drainage holes back to the pan are pretty much the same on all the 3.8/4.2 engines, and no changes were made to those parts to coincide with the change in spec from 5w30 to 5w20, so that tells me that the change was done for gas mileage only. On an engine that was designed from the ground up to use a 5w20 or 0w20, go ahead and use it, but retrofitting thinner oils into older engines is not doing the engine any favors.
 

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Yeah, definitely stay away from 0W-20. The bearings on my '96 Mark VIII's original engine spun and let go 1000 miles after I gave that a try!
 

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Discussion Starter · #6 ·
I just went with good old Motorcraft 5W-30. It can't do any harm. The old oil was black black (possibly due to me adding Seafoam about 300 miles ago).

But isn't that oil filter in an awkward spot?! Impossible to remove without making a mess.
 

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Put a piece of tin foil over the part of the frame and wiring cable so the oil doesn't collect behind the cable and drip for days.

And to the original question, we did not lose any gas mileage going from the recommended 5W20 to 5W30 on our '04 Crown Vic, and the engine sounded a little quieter. 5W30 is the way to go with these engines.

Al
 
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Discussion Starter · #8 ·
Put a piece of tin foil over the part of the frame and wiring cable so the oil doesn't collect behind the cable and drip for days.
I'll know better next time.

and the engine sounded a little quieter.
This may be premature because I haven't driven yet. But just starting the engine after the oil change felt much smoother. Yay!
 

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I've read that the lash adjusters in the heads are designed for a specific oil weight. 5w30 for our cars, and 5w20 for the newer ones. IDK if that's correct, tho.
 

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This may be premature because I haven't driven yet. But just starting the engine after the oil change felt much smoother. Yay!
Over the years, I've noticed a bump in gas mileage right after an oil change on most of my cars.

The tinfoil idea came from another member. You wrap that frame piece, and the tinfoil is a smooth surface for the oil to run off.

Al
 
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My 97 4.6l called for 5w-20 and I am at 305,000 original miles. I changed to full synthetic at 500 miles and it has been 5w-20 except for dead of summer where I'll sub in a 5w-30 or 10w-30 with 4 qts of 5w-20. I still get 22-25 mpg on highway. My oil pan has been leaking since 100k but only about 1/2 qt between changes at 5-7k intervals. Sometimes I hear a dry startup which tells me the bearings are getting worn which is why I add a little heavier oil in the mix as it helps the oil wedge hold together. I've rebuilt one of those famous 3v 5.4l and the old engine had decent bearings at 190k. The oil pump and the thrust bearing was a disaster so the tolerances at factory should use the designed weight unless you know it needs a little thickening and then don't over do it.
 

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You do not want to use Lucas or any additive that makes it stick to the chains; Our engines do a thing where most of the oil can be in the heads at high rpm anyway, they don't need help.
You Can run the entire engine oil contents out the PCV valve and vacuum circuit. (10 miles at ~5krpm.)
 
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1994 Cougar XR7 DOHC/5-Speed
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I've read that the lash adjusters in the heads are designed for a specific oil weight. 5w30 for our cars, and 5w20 for the newer ones. IDK if that's correct, tho.
They鈥檙e the same, all Ford did was change the spec. @nickmckinney was an advocate for Rotella 5/10/15w40
 
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