Dan

Are there any negatives to using the Ford GT's and GT500's 5w50 oil in a Mustang GT?

My parts guy can get this oil for less than the Ford Full Synthetic 5w20 oil. I would think that having a slightly thicker oil during summer use (especially when pushing the car occassionally) is okay.

Thoughts?

Dan

Oh, and I am aware gas milage will suffer slightly.

70MACH1OWNER

Dan,
I don't believe the oil isn't any thicker. It is still 5W oil but has additives to give it the protection value of a 50W oil. I think that is how it works. And "yes" I remember you!
Scott

Bullitt995

Don't bother. I remember 5w50 being quite expensive and there's no reason to waste money on something that only has the possibility of decreasing performance.

theedge67

I would have no problem using a 5-30 (I've done it, and may again). But a 5-50 is too thick for these engines. I doubt you would see any more protection than a 5-30. I could see using the 5-50 in a supercharged application, but nothing N/A. With such a wide viscosity spread, I bet the oil would shear like a mother and actually be about a 5-30 after about 1500 miles anyway.

70MACH1OWNER

Guys,
I really don't think that 5W-50 is any thicker...just has more additives to give the protection of a 50W oil. Do you really think a GT500 can pump 50W oil and our GT's can't. I am sure the oil is not 50W. It is 5W with the additives to protect like 50W.
Scott

Bullitt995

5w-50 is definatly thicker than 5w-20. That's what the second number is, weight. First number is viscosity. There are parts of the 3v blocks that have to flow oil that are too small for a heavy oil like 5w-50. And why even bother with this oil? You won't gain anything from it. It's like trying to run deisel just to see if you can. It can only end up in tragedy.

281GT

5W50 behaves like a 5w when it's cold and a 50w when it's hot. So you're going to force your oil pump to push around that heavy oil when it's completely uneccesary. Unless you're got a loose bearing or an oil burner there is no need to use oil that's heavier than neccesary. Modern engines also have might tighter clerences than older engines do and by using thicker oil you may even be taking a chnace that the thick oil will not get into those tight areas very well.
Stick with 5w20 or 5w30 if you want longevity and best performance from your engine.

theedge67

That doesn't make any sense. I know a little about oil, and that is not true. Where are you getting this info? For the oil to be API certified and be called a 5-50, it has to be of certain viscosities at certain temperatures. At X temp (low temp) it is of X Viscosity (thickness), therefore gets a 5 rating. At Y temp (high temp) it is of Y viscosity, getting a 50 rating. Yes, additives are what make the oil thicker at high temps, but the oil physically is thicker. It doesn't just protect better because of the additives, it protects better because it IS thicker.

Now, whether you need more protection from a thicker oil is a different story. I don't see a need in a N/A car, and I have Used Oil Analysis to back it up.

RadBOSS

Pushing the higher viscosity oil around accomplishes the following.

a) more parasitic losses to pump the thicker oil.
b) the oil will run hotter because more will be going over the relief valve
c) because more is going over the relief valve, less will make it to the bearings and valve train.

Stick with the multivis 20W unless you start to see some oil consumption. Then try multivis 30, or more if you have to, but going to a 50W multivis on a new engine is not thinking smart.

metroplex

The Ford GT and GT500's 5.4L quad-cam V8 engines do not have VCT (Variable Cam Timing) and can run 5W-50, just like any of the 4.6/5.4 2V/4V engines. The 4.6/5.4 3V engines are equipped with VCT and require a xW-20/xW-30 to operate properly. If you disabled VCT, then obviously you won't have this limitation.

Chrysler's MDS malfunctions when using thicker engine oils.

Bullitt995

Fine, put the 5w-50 in your car. Just make sure you video tape it, I need a good laugh.

70MACH1OWNER

At this point I will assume you are correct that the 5W-50 is thicker. What upgrade does the GT500 have that it can pump 50W oil in the dead of winter and our GT's can't?
Scott

70MACH1OWNER

So the GT500 had looser tolerances than our GT's so it can run the 5W-50 oil? Still not buying this guys! Please somebody provide some proof. Also, are you saying when you drain you oil at 0 degrees in runs like 5W oil and when it's hot (normal operating temp) the oil drains like 50W?
Scott

Bullitt995

Read metroplex's post. It has to do with the VCT and block designs.

Dan

Sounds like I will be switching back to 5w20 or 5w30 full synthetic.

My next oil change will be in January. Due to the lower winter temperatures I assume that I should be okay with the 5w50 for a few months, correct?

Bullitt995

I would switch it out by the end of the day if I were you.

RadBOSS

MustangRetribution

+1 you can pick up that information in any automotive text book.

typicllay thicker then recomended oil is used for high mileage worn engines, it will help seal rings and provide better bearing protection.

the tolerances in these engines are really tight, and the hydralically controlled valve train makes me wary of using anything other then 5-20, 5-30 be as high as I would go

RadBOSS

It would be interesting to see the clearance specs for the GT500. Looking at the specs for the 4.6L 3V its not particularly tight.

And yes when 5W-30 is cold if flows like 5W and visa versa.

Multivis oils have additives called 'Viscosity Index Improvers' (long chain coil polymers, which are temperature-reactive), in the oil and will increase its viscosity as it heats up to its full operating temperature.