http://corner-carvers.com/forums/showthread.php?t=36607

This has been discussed at length on various mustang boards and I always refer people to this thread. Although this is referring to Mod motors, especially 4 valves, I think this applies to Coyotes too. Pay special attention to what Scott White (swhiteh3) says. According to him, he spent about 10 years doing engine development with Ford Motor Company, including being the systems engineer on the 2003 Aviator and 2005 Mustang V8s.

On a personal note, I switched from 5W-20 to 5W-30 on my 2003 Mach 1 and noticed valvetrain noise reduced and the occasional startup clatter completely eliminated using only motorcraft oil filters. On my STX 5.0, I'll probably switch to 5W-30 full synthetic at 10k miles.

 

Then explain why a boss mustang recommends 5w-50 oil factory?

I have built over a dozen 5.0 engines over the past couple years, and will tell you that the tolerances of a regular 5.0 in the gt mustangs and the 5.0 in the boss mustangs are exactly the same. The oil passages did not change, bearing clearance did not change etc. In each of the engines below, I will run nothing but a quality 20w-50 synthetic oil.

Just for reference:

I fabbed this fogger kit for a built 5.0. Car made 548 rwhp na and just a tick under 800 rwhp on a 250 shot.


This car has an F1-A with a built engine. Made just under 1000 hp to the tires on 18 lbs of boost.


This is a 2011 gt500 with a built engine and a kenne bell 3.6 blower. Made 1021 rwhp on 21 lbs of boost.


Using 5w-30 will have 0 ill effects on the engine.

 

Interesting that a Ford engine developer says he wouldn't run a 20wt instead of a 30 wt, and that the mileage penalty is not worth the long term wear penalty.

However it sounds like he was referring to the 4.6 and 5.4, correct me if I'm wrong but he didn't mention the 5.0? Not trying to argue, just getting some info. I'd prefer to run a 30 weight myself.

 

Correct. But I'll refer you to the first sentence on Blackpony's post above yours. The same applied to the GT500's. They also required 5W50.

 

The cam hydraulics keeps me running a 20 weight in my 2011. 0w20 QSUD for this winter and 5w20 of whatever brand name synthetic is cheaper for the warm weather.

I am keeping an ear oN these 30w discussiona, though.

 

ehh, I use 5-20 Motocraft blend on all of mine (4 vehicles), zero issues...

 

The coyote wasn't out yet when that thread was active.

 

Whups yeah thanks, just looked at the dates on that...

 

I might have to start going back to the dealer for oil changes. They changed the slurpee flavors at my vavoline. =-(

 

The main thing to keep in mind is how you drive the vehicle. If it is purely a daily that you putt to work and back then the 20w is just fine. If you do much heavy hauling and towing very often or you like to have fun and drag race it occasionally then i would suggest going with a 30w oil. The added stresses and loads on the engine can cause the oil to break down faster and break through the oil film on the bearings thus causing metal to metal contact and damaging the bearings. Even if you prefer to run the 20w oil, keeping it changed on time with a quality oil and filter will tremendiously extend the life of your engine. I personally run an amsoil synthetic oil, i change the oil and filter every 6k miles and change just the filter every 3k miles.