So I had my 2013GT 5.0 oil changed the other day at a place I've used for years for car service with no trouble.

However in my last visit there was a possible mix up in that they *may* have put in 5w30 instead of 5w20. Some of their paperwork said 5w30, some said 5w30. The "technician" claimed it was definitely 5w20.

Now, for non-performance car I wouldn't be worried. I'd just ensure 5w20 in the next change. However, with this Mustang, which I assume has a bit tighter tolerances than typical (and definitely has higher RPM) and may actually require 5w20 to properly lubricate. I'm not sure. Any of you knowledgeable folks have any advice?

 

You'll be fine. Some people run 5W30 in their coyotes. Track pack equipped cars run 5W50, while standard GTs use 5W20.

 

I doubt it would hurt anything but I believe the technician is probably right. 5w20 was most likely put in your car. Probably just a clerical error.
If it's going to bug the heck out of you for the next 3,000 - 5,000 miles, just get another oil change.

 

Lose no sleep. Your engine will thank you for it.

 

I completely understand your concern. An oil change should be a basic and simple service anywhere......however, I do bring my own synthetic oil to the Ford dealer where I purchased my CS and still feel compelled to check the crank case oil level..... It has once been over filled. The weight of oil in your case would not be as much a worry. At the end of the day, you can't take anything for granted.