Mustang Coyote 5.0L V8 engine oil recommendations - Ford has spec’d 5W20, 5W50, and 5W30 for it before.

ZeeOSix

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Sorry, I think you misunderstood my question. I asked how not why? In what way might an engine suffer? How would a heavier oil harm an engine, and in particular, this engine?
5W-50 on the streets isn't going to hurt that engine in any way ... but it's not really going to be needed for that engine on the street IMO, 5W-30 should be plenty. When Ford speced 5W-20, most Mustang owners just bumped up to 5W-30 on their own.

Ford specs 5W-50 for the BOSS 302 (basically the forefather engine dubbed "Roadrunner" to the Coyote) and the GT500. Seems they did that so guys could go to the track and not have to change to a thicker oil for track use. Ford would not spec 5W-50 for those engines for all time use if there was any danger of harming the engine while street driving. The BOSS 302 and the GT500 have basically the same bearing clearances as the Coyote. In fact, engine journal bearing clearances have been basically the same for decades in cars, trucks, motorcycles, etc.

Another misconception that keeps on living is that engines are "designed" around an oil viscosity. How could that be true when engine makers use to specify a whole range of oil viscosity for their engines? Motorcycle OMs still call out a range of viscosity ... but motorcycle makers are not tied down by CAFE. The reason you see one low viscosity call out in OMs these days is because of CAFE ... not because of engine design done around an oil viscosity. The wrinkle here is that engines speced to run 0W-8 and 0W-16 may have "design for" aspects to run oil that thin ... but you could still run thicker oil in them and not do any harm. Toyota even has a statement in the OM of their vehicles that eludes to running thicker oil than the speced 0W-16 if the vehicle was to be used harder.

Engines don't mind thicker oil, but may not like thinner and thinner oil ... that's just the way that tribology works. At some point if the oil starts out thinner, and also gets thinner as it gets hotter, the MOFT between moving parts can go to zero and stuff starts getting damaged. There's a reason why makers of high performance cars say to use a heavier oil for track use, or even to use a heavier oil for street driven vehicles if they are used in more demanding conditions.
 
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Ford in the past has been a stickler on recommended oil viscosity adherence. I remember them not honoring warranty for main bearings when people used 10-w30 instead of 5-w30. This was the 4.6 engine.
I used 0-w20 in a 2018 and 2019 F-150 with the 5.0 engines. Put 55,000 on the 2018 in a year.
At the time the 0-w20 was more readily available than the specified 5-w20. At local Walmart the Motorcraft blend was same price as Full Synthetics. Did use the Motorcraft filters
 
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A 5W-20 at room temp is still more viscous than 5W-50 at operating temp. So, as already mentioned, engines aren't designed around viscosity. Viscosity is determined by ambient temps and intended usage. I vote for M1 FS 0W-40 across all duty cycles, unless the engine just lives at the track 60%+ of the time, in which case 5W-50 does make sense.
 
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I'm sure 99% of the 5.0 engines in service live a long life on 5w20 /5w30 oil .
would't lose any sleep over using the 5w30. i have 60000 miles on my 15 , its been fed 5 and 0w20 and now running 5w30 for the last few years.
probably one of the best running engines i have had.
 
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Ford in the past has been a stickler on recommended oil viscosity adherence. I remember them not honoring warranty for main bearings when people used 10-w30 instead of 5-w30. This was the 4.6 engine.
That makes zero technical sense whatsoever. Can you explain how this dealership determined the winter rating of the oil? And just how many warranty denials are we talking about here? A warranty denial would have to be because the oil caused a failure. This will not happen because of a different winter rating.
 
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My boss at work has a 20 or 21 mustang 5.0, put a supercharger on it, sees some track time. I asked him yesterday what oil he runs, he said PUP 5W30 summer, 5W20 in the winter.

He said he changes it between 3000-5000 miles, mostly around 3000 because of the supercharger
 
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Engine was designed to run on a 20 or 30 weight. If you’re just daily driving the car, why would you want a 50 weight in the sump? Now if it was seeing a lot of track time, high rpm’s, higher oil temps, I’d see more reason of course.
My 2017 Accord Sport says 0W20 on the oil cap, I have M1 0W40 in it. It’s just my daily driver/commuter car. Usually have the cruise set at 65mph in the right hand lane.
Everyone has their opinions and are free to do what they like
I do agree with your last sentence
 
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The old “tolerances” thing. The use of that term shows that the person doesn’t know what they are talking about but only repeating something they have heard or read on the Internet.

Also "clearances!"
 

ZeeOSix

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That makes zero technical sense whatsoever. Can you explain how this dealership determined the winter rating of the oil? And just how many warranty denials are we talking about here? A warranty denial would have to be because the oil caused a failure. This will not happen because of a different winter rating.
There is no explaination except the only way a 10W could cause damage when a 5W wouldn't, was if the start-up was so cold that the 10W lost its pumpability, when a 5W would still pump.

It's been known that some Ford dealers will try to deny warranty on anything for any excuse. And some people fall for and accept it because they don't know any better. Those Ford dealers denying warranty for using 10W were probably in Florida. 🤑😄
 
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I use any brand 10w30 synthetic oil in my wife’s Mustang. ZERO need for a 50 weight oil in a Coyote engine even if it’s making 900 horsepower.

I once used 10w30 Mobil 1 and 10w30 Rotella T5. Engine absolutely purrrrrrrs like a kitten with this blend @ 7500 RPMs.


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The old “tolerances” thing. The use of that term shows that the person doesn’t know what they are talking about but only repeating something they have heard or read on the Internet.
Tolerances are the allowed variations of the blue print specified clearances, We can tell who actually knows things posted here.
 
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A 5W-20 at room temp is still more viscous than 5W-50 at operating temp. So, as already mentioned, engines aren't designed around viscosity. Viscosity is determined by ambient temps and intended usage. I vote for M1 FS 0W-40 across all duty cycles, unless the engine just lives at the track 60%+ of the time, in which case 5W-50 does make sense.
I would if mine, probably run a euro 5/40. Now in hot summer maybe M1 15-50. But I tend to drive engines hard and run short OCI 5k
 
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