I bought some Mobil 1 5W-30 motor oil for my 05 GT.

I know the manual says I should use 5W-20.

I actually thought I was buying 5W-20 - guess not.

I bought it here:
http://www.brenspeed.com/mustang_2005/oils.html

Am I OK using this oil in my car?

 

5W-30 is totally fine for your GT engine. Remember that when 5W-20 oil is at operating temperature, it is phenomenally thin (about 50 Saybolt).
Keep in mind this definition of a 5W-20 oil:
It behaves like a 5 weight at 0F
The "W" means "safe for Winter applications"
It behaves like a 20 weight at 212F.
By the viscosity tables, I read the following Viscosities:
a 5 weight oil has a viscosity of about 3,000 Saybolt at 0F
a 20 weight oil has a viscosity of about 50 Saybolt at 212F
a 30 weight oil has a viscosity of about 65 Saybolt at 212F
a 40 weight oil has a viscosity of about 70 Saybolt at 212F
a 50 weight oil has a viscosity of about 95 Saybolt at 212F
So, if your top number is 20, 30, 40, or 50, they are all far thinner than 5 weight at 0F. You won't hurt your engine, and actually would protect it better with a higher second-number oil. These thin second-number oils are all about fuel economy. Note that the new Shelby REQUIRES 5W-50 because of the bearing loads, so you know that the thicker-at-temperature oil will work in engines of this general design.

 

I just did a used oil analysis on my 5W30 oil and have found over the course of several different analyses that the 5W30 oil shows lower wear numbers than 5W20 oil. I will post the analysis sheet for you tomorrow so you can see for yourself that 5W30 oil has had a positive effect on engine wear in my situation.

 

what is your "situation"?
I am curious about this as well, since I noticed you live in st louis, I am in KC so we share the same climate basicly.
costco sells 6 quarts in a pack of mobil 1 5w-30 and I have been tempted a few times to buy it instead.

 

5W30 will be fine. I used the Motorcraft semi-syn 5W20 from the beginning due to concerns about the VCT supposedly being finicky regarding oil weight. After getting a few oil analyses back after track days and seeing viscosity break down to the point where it was no longer even in the 5W20 range (which is already thin!), I decided a change to a heavier weight was needed.

On a different forum, one frequented by current and former Ford engineers, one of the engineers on the 4.6 3V engine team made it very clear that running 5W20 in our engines is ONLY for emissions and is actually harmful to longevity! He recommended 5W30 at a minimum, if not a 40 weight for hotter climates.

I'll be giving Mobil 1 5W-30 a go this year.

 

What forum is it?

 

PM'd you with the link.

 

Most newer cars (all makes) "require" 5-20. It is absolutely for over all C.A.F.E. (fleet fuel economy) rating and emissions. You will be fine with 5-30.

 

I really wished this topic have posted sooner. I just did an oil change on Friday using Mobil 1 5W20 Well, maybe next time.......

 

I have heard the thinner oil is used in our applications and req'd due to tighter bearing tolerances in the bottom end??

 

Not true. 5W30 will do the same job as 5W20, regardless of bearing tolerances.

 

I've been using Motul 8100 5W30 since I switched over to synthetic and unlike some of the nay-sayers on this forum, my car runs quite strong. I ran 0W40 in my A4 for 5.5 years (despite the manual asking for 5W30) and it was a-ok.

Thanks for the sound advice Gearhead.

Kristina

 

Would you please give me the link where the Ford engineers made those comments, thanks.....

 

It's interesting that the Royal Purple they sell is 5W20 and the Mobile One is 5W30? They are both synthetic oils.

 

I use RP 5W20...Mobil One doesn't make a 5W20 ?

 

Yes, mobile 1 does make 5w20.


This thread has me thinking of maybe I should go to 5w30 for track days when the rpm's are a constant 4000-6200 rpmss for a good period of time.

 

Yes they do old man.......shop at Walley world!!! It's like $29.99 for a 5 quart jug!
Scott

 

Hey older man than me ! I was not saying that Mobile one did not make 5W20 I was asking a question notice the ? mark ! previous threads seem to imply they didn't !! I wouldn't know ! I don't use inferior oils like Mobile One !.....

 

So ti sounds like the 5W-30 is safe for our cars, but alot has been mentioned about emmisions. Would using the 5W-30 cause a problem at the inspection station????