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5W-20 or 5W-30

786
1,069
Exp. Type
W2W Racing
Exp. Level
3-5 Years
Huntsville, AL
So I am a complete newb on late model Mustangs...Ok that's out of the way. I recently purchased my wife a used 2021 GT 5.0. As of today it has 10K miles on it and since I do not know the history of the oil or the last change, I plan to change the oil and filter this weekend. However, I am a bit confused on what weight oil to use. The owners manual recommends 5W-30...which is what I will likely use. However, I have read on a couple well known websites that say to use 5W-20. Why is this?

We live in North Alabama and I use 5W-30 oil in all of our other newer vehicles which recommend 5W-30. So this is more of a curiosity as to the disconnect...at least from what I am reading.
 

TMSBOSS

Spending my pension on car parts and track fees.
7,074
4,442
Exp. Type
HPDE
Exp. Level
10-20 Years
Illinois
Patrick

I looked at the manual also. Ford says 5W-30 and the car should still be under warranty. Not a hard decision there.
Why do other sites list 5W-20? I could guess. Or better yet assume others are guessing. Why deviate away from the recommendation of the company which owns replacement under warranty? The big step in cost come when you jump up to 5W-50.
I bet you need a roll bar for that car. Got to keep Holly as safe as can be. :rolleyes:
 
54
39
Exp. Type
HPDE
Exp. Level
Under 3 Years
Atlanta, GA
Short answer: 5w30.
2015-2020 s550s specifically have had '5w20' written on their oil cap but their manual also specifies to run 5w30 on the track
From 2021+, they decided to replace 5w20 recommendation all-together and their oil cap now reads 5w30 as well.

Not all websites are always 100% correct with their information. Always go by your owners manual. No big deal
 
786
1,069
Exp. Type
W2W Racing
Exp. Level
3-5 Years
Huntsville, AL
Going off topic here, but I'm trying to learn what I need to do maintenance wise for these cars. I was studying the owners manual this afternoon and have some additional questions...not related to oil.
The owner's manual states it has a lifetime fuel filter. How is this possible?
The owner's manual states it has lifetime rear gear oil (unless submerged in water). Really?
I may have overlooked it, but I didn't see a change interval for manual transmission gear oil.
Not being a track car, are there any benefits to a cold air intake with conical filter for these engines? I see the Mach 1 comes from the factory with one.
 

Dinosoar

Dinosoar Motorsports
16
9
Exp. Type
Time Attack
Exp. Level
10-20 Years
Northern Virginia
This has always been a difficult debate with the "It's what the factory says" camp, and the "That's just for MPG" camp. Same arguments in the BMW forums.

For track duty, this is, IMO, a critical question though, and using 0W-20 seems potentially problematic. Ford is the only manufacturer (that I'm aware of) that suggest (for the Coyote) heavier oil for track use. I don't know if that translates to the 4.6 (2V, 3V, or 4V) series of engine or not. The concept of heavier oil may translate to any engine, so are there aspects to the oil and engine design (e.g. tight tolerances) that suggest one should keep a lighter weight regardless of the use case?
 
Last edited:
569
526
Exp. Type
HPDE
Exp. Level
5-10 Years
Lenoir City TN
Going off topic here, but I'm trying to learn what I need to do maintenance wise for these cars. I was studying the owners manual this afternoon and have some additional questions...not related to oil.
The owner's manual states it has a lifetime fuel filter. How is this possible?
The owner's manual states it has lifetime rear gear oil (unless submerged in water). Really?
I may have overlooked it, but I didn't see a change interval for manual transmission gear oil.
Not being a track car, are there any benefits to a cold air intake with conical filter for these engines? I see the Mach 1 comes from the factory with one.
Just remember that Ford only needs to get it past the warranty period. Then it is your problem. The automatic transmission used in the Fusions have a 150,000 mile change interval. Even my Ford dealer has said that is too long and if you let it go that long don't be surprised if it slips after the first scheduled change.
 

TMSBOSS

Spending my pension on car parts and track fees.
7,074
4,442
Exp. Type
HPDE
Exp. Level
10-20 Years
Illinois
30
13
Exp. Type
HPDE
Exp. Level
Under 3 Years
California
I have a dual-purpose car. My 5.0 is not daily, is mostly a weekend car that sees some occasional track days.

Would running a good brand 5w30 such as Amsoil Signature Series or Redline be good enough for a weekend car that sees some occasional track time?
 

Bill Pemberton

0ld Ford Automotive Racing Terror
7,220
6,448
Exp. Type
Time Attack
Exp. Level
20+ Years
Blair, Nebraska
I will jump in here and reiterate what many have stated ( 0-20W was for fuel efficiency ) , but the transmission and rear end fluid should be changed way, way more often if the car is tracked. Over the years the Ford and Dodge Performance Engineers I was fortunate enough to be friends with all recommended much more frequent fluid changes for the transmission and rear end than what the manual suggests. A little common sense with the MT82s issues means many folks have changed the fluid more often just as a preventative measure, but the same situation is relative to the automatic or Tremec systems. The rear end, just think about a rear diff cooler so many have or want, and that also screams, change me more often.

Take the old manual from the Boss 302S race cars and they suggest changes after 4 hours of track time. Now that may be too aggressive for some doing HPDEs or Time Trials, but it also lets one understand those extremely long intervals for changing fluids is a bit ridiculous. Most change their oil based on track time, so do your other fluids using the same logic and brake fluid is the other liquid that should be done quite often.

Sorry, but over the years listening to Engineers and other racers, it often seemed like the guys/gals who were replacing rear ends or trannies tended to follow manual guidelines and not hard usage notes --- virtually every manufacturer tells the owner to change things more often based on harsh conditions ( read -- track time ).
 

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