5W-20 synthetic blend or 5W-30 full synthetic?

[nick20s]

I heard from this awesome former Ford technician in the video below that Ford recommends 5w-20 synthetic blend just to meet cafe standards for fuel efficiency and to prove low cost of ownership, but actually the 5w-30 full synthetic is the best for engine protection.

Is this true for 2019 Mustang GT?

Will 5w-30 full synthetic void the manufacturers warranty?

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[Zinc03svt]

I have been on 5w-20 for 8k miles. Switching next change to 5w-30 PUP.

 

[Landis]

This is what I run in my 18. No tick or anything. https://www.drivenracingoil.com/fr50-5w-50-synthetic-street-performance-oil.html

 

[nick20s]

I have been on 5w-20 for 8k miles. Switching next change to 5w-30 PUP.

Do you change the oil on your own? My dealer doesn’t use PUP.

 

[Kermitz]

Been running Motorcraft 5W30 Full Synthetic since my first oil change. Car is much quieter.

 

[Deleted member 35786]

Since you live in the south you can run 10w-30. The w is for winter in oil viscosity weight. No need for 5w unless your driving in sub zero temps.

 

[Dfeeds]

There's.... a lot of unqualified information on the subject.

I could write you an essay so I'll try to keep it brief. 5w20 has a lower optimum operating temperature than 5w30. Basically, 5w20 will be the same viscosity, at 200°F, as 5w30 is aroind 220°F. The temps vary wildly based on manufacturer.

On paper, if you drive your mustang like a prius for max fuel economy, 5w20 is just fine. However, 5w20 starts to thin out way too much when it gets hot, and this is where many are hesitant to use it. My pp1, with the bigger radiator, stays at about 200° and around 199 to 205° cylinder head temps when I'm just cruising around town. But if I'm on the expressway or get on it at all, that temp shoots up pretty quick. These engines run hot, there's no other way around it. 5w30 gives you much more wiggle room.

The other issue is, being direct injected, fuel dilution. This can cause that 5w20 to sheer to something else over time, and same with the 5w30. This is why I personally recommend full synthetic, regardless of which viscosity you choose.

The counter argument floating around is bearing temps. A newer field of thought is that 5w20 is better because it can pass through bearings easier, allowing them to cool down more. Cooler bearings = longer lasting bearings. This does not account for the rest of the engine, however. The very reason why 5w20 is better for bearings is why many don't trust it with their engine. It flows too well, and doesn't leave a protective film (there's a technical term but it's escaping me).

There's also people in the school of thought that the additive package does more for protection than the oil, so using 5w20 or 5w30 is almost irrelevant, as long as you adhere to the max temperature ranges.


If you search BITOG (bobistheoilguy) you'll find a lot of oil analysis reports that show 5w20 not protecting as well as 5w30, and vise versa. There's no proof 5w20 will blow your engine. The difference in longevity could also be meaningless if you have no intention on keeping the car passed 100k miles. In that case, you'd have to base your decision based on your driving habits. These cars have an oil temperature sensor that, while not an actual sensor in the pan, has been tested to be very accurate. Utilize this.


There were a string of posts from two ex ford engineers, over a decade back, claiming that 5w20 is purely for cafe. One said that he tore into hundreds of Ford modular engines and, based on what he saw, flat out said to not use 5w20 if you care about your engine. 5w30, in his opinion, was simply "okay" for street use. However, that was before the coyote's time, and oil formulations change annually, so it's outdated. Well, to a degree. Oil formulations evolve rapidly but the specs of the 5.0l (clearances and such) don't indicate it's anywhere near different enough from the 4.6l (which used 5w30, then 5w20, then back spec'd to 5w30) to warrant any change in oil viscosity. However, these cars (last I checked) are spec'd for 5w30 everywhere else around the world. That info alone is enough to convince many to use 5w30. There's also counter arguments to that, as well. One being that oil is more expensive in europe so manufacturers spec based on longer drain intervals, and such.


Bottom line is that you'll give yourself a serious headache trying to decide. This whole argument has been going on for a damn long time. Not too long ago, you were considered insane to run 5/10w30 over 5/10w40. 5w30 was only meant for, wait for it... CAFE standards. See a trend?


The general consensus seems to come down to this: if you're going to drive your Mustang for maximum fuel efficiency then run 5w20. If you're going to drive this car like one would expect someone who just bought a gas guzzling v8 in a time where gas prices are absurd, then use 5w30.

 

[Bullitt0819]

Applies to the 4.6L Modular, but AFAIK the Coyote is somewhat derived from the Modular:

http://www.agcoauto.com/content/news/p2_articleid/115

TL;DR: "Ford originally specified a 5W30 motor oil for the engine. They soon found this caused oil consumption and possible catalytic converter problems. This caused a change in the specification to a 5W20 or a 5W20 synthetic blend. It is also believed the lower viscosity oil can travel to the timing chain tensioners more quickly. The oil filter they designed for the engine also has a specific anti drain-back valve and for good reason."

 

[Mustang Tony]

Running 5w 30 full synthetic since 1k miles. It's in the manual.

 

[Zinc03svt]

Do you change the oil on your own? My dealer doesn’t use PUP.

Yes, but with the large diameter drain plug it makes a mess. I will more than likely just take it to local shop w/ my oil/filter/plug. They can do it a lot faster and probably worth 20 bucks.

 

[Dfeeds]

Yes, but with the large diameter drain plug it makes a mess. I will more than likely just take it to local shop w/ my oil/filter/plug. They can do it a lot faster and probably worth 20 bucks.

Large pan and one of those oil absorbing matts make it a piece of cake. The upfront cost of it all may be higher than taking it to a shop, but that'll recoup over time and I have the added security knowing that I'm doing it properly.

 

[nick20s]

This is interesting. In Australia it is 5w-30!


https://www.mustang6g.com/forums/threads/2018-mustang-gt-recommended-oil-in-australia.119584/page-2

 

[shogun32]

Furthermore 5w50 is right there in the manual if you're subjecting your engine to "severe" usage - aka Track Days. If you're debating what brand and formulation to pick get the technical data sheets and read the details. Viscosity expressed as ## cSt@40C and 100C is what you're looking for - if memory serves 12cSt@100C is the 'rule of thumb' goal. Short of the arctic, 10 weight when cold is fine but Full Synth 10w30 is not very common anymore. In the summer I put in a mix of 5w30 and 10w40.

As an example
http://www.royalpurple.com/wp-content/uploads/2019/01/RP-PDS-HPS-2019.pdf

 

[Zinc03svt]

Large pan and one of those oil absorbing matts make it a piece of cake. The upfront cost of it all may be higher than taking it to a shop, but that'll recoup over time and I have the added security knowing that I'm doing it properly.

Oh I will be watching. ;).

 

[Condor1970]

I switched to QSUD 5w30. Engine runs strong and smooth. Quieter than when I used to run Mobil 1 5w30.

540RATblog has recently tested the latest formulation of QSUD 5w30, and it has a much better sheer strength than just about anything readily available in 5w30. He also found the new formulation of QSUD increases in sheer strength as temperature was raised to 275F. That is very rare. I'm starting to wonder if QSUD didn't add a small amount of PAO synthetic to their 80% GTL base stock. This is the recent data he got testing it this summer.

12. 5W30 Quaker State Ultimate Durability, API SN, GM dexos 1 Gen 2, synthetic (green bottle) = 120,588 psi, which is about a 6% “improvement” over the previous version of this oil.
zinc = TBD
phos = TBD
moly = TBD
This was the newest current version of this oil when it was tested Summer 2019. This version was updated to carry the GM dexos 1 “Gen 2” certification. The previous version did NOT have the Gen 2 certification. The psi value of this oil, which came from testing it at the normal operating test temperature of 230*F, put it in the FANTASTIC Wear Protection Category.

However, I went on to also test this oil at the much higher temperature of 275*F. At that elevated temperature, any hotter and thinner oil typically experiences a drop in Wear Protection Capability. But, this oil actually had a 4% “increase” in capability. At that elevated temperature, it produced an extremely impressive 125,493 psi, which further improved its position in the FANTASTC Wear Protection Category.

I also tested this oil to find out its onset of thermal breakdown, which was 270*F.

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For those wondering. Motorcraft Synthetic blend doesn't do very well compared to most high quality full synthetics.

178. 5W20 Motorcraft, Friction Fighting Formula, API SN, synthetic blend = 72,144 psi
zinc = TBD
phos = TBD
moly = TBD
This oil was tested Summer 2017.

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