2cokeman

Is this full synthetic by Castrol Syntec 5w50 OK in for our cars, it is a lot cheaper at the parts store than the mobil i at the dealer.
Thanks!

2cokeman

I was searching some of the performance shops and Evolution uses the Castrol in there GT500 oil changes.

Unleashedbeast

Castrol Syntec 5W-50 has been used frequently in the GT500, although it is not the best choice IMO. 50 grade lubricants are too viscous for use in the Shelby for street duties, aggressive driving, and drag racing. Unless you are road racing, I see no need for a 50 grade lubricant, and why I am now testing 10W-30 Amsoil.

Motorcraft 5W-50 quickly shear to a heavy 30 grade lubricant after ~2,000 miles. Castrol shears to a 40 grade lubricant after ~2,000 miles. I've been doing a lot of testing using lighter lubricants in the Shelby with great results, both on UOA and pressure testing. Check out the links below. In defense of the heavier 50 grade lubricants, it's a good thing they shear, as the Ford modular has no need for such a heavy lubricant for street duties.

Oil thread #1

Oil thread #2

Oil thread #3

nmd55

interesting!

REDBOSS1

When running different oil does it void the warranty? I would hate to do this and something break and the dealer give me the ole "well you weren't running the 5W-50 that you were supposed to so it's not on us."

Lifter583

As long as the oils meet the specs called out by the book...all is fine

Unleashedbeast

Assuming that 99% of all techs @ Ford would have no clue of the difference. No way. The 1% that do would know what you were running is superior to the MC 5W-50 formulation. An oil analysis would confirm that a robust 10W-40 true synthetic specs were as follows.

• TBN is greater than 1.0
• Viscosity is greater than 12.0 cSt @ 100*C
• Oxidation is in a safe range (less than 60)
• ZDDP is greater than 600 ppm

Soon as the above numbers were confirmed, the lubricant would be ruled out to have caused any engine failure.

I've proved time and time again, 50 grade lubricants are too viscous for use in the Shelby for daily driving, aggressive street use, and drag racing. In fact, I would trust a robust 10W-40 for even 20-30 minute session road racing.

Even if the lubricant chosen doesn't have Ford's spec on it, what I have posted above will apply.

2cokeman

If 5w50 is not good for Shelby then why does Ford use it??? And I am pretty sure Castrol is no better or worse than Ford or Mobil 1

Unleashedbeast

I didn't say it wasn't sufficient, I just said there are much better options.

Ford has a spec that covers only 3 cars in their entire vehicle fleet. One of which has an engine with an extremely close brother that requires 5W-20.

I'm surprised more people are not opening their eyes and the profit potential that is involved with this. Every other oil formulator that once carried this spec has recently dropped it. (i.e. Castrol). Castrol 5W-50 in fact has shown better UOAs than Motorcraft 5W-50. If I were to use a Mobil 1 formulation, I would choose 0W-40 over their 5W-50.

Anyone who thinks their Shelby engine will fail if you do not use this spec is wrong, and that person needs to study engine lubrication technology more.