my mustang gt says premium unleaded below the speedometer,but i have never heard anyone say anything about that?all i heard is to run regular unleaded.

 

Premium is unnecessary, I run 89 octane in my '06 GT. Regular is fine as long as you don't experience any pinging in your engine...

What is pinging you ask? WIKI!

http://en.wikipedia.org/wiki/Engine_knocking

The computers in most cars today will automatically adjust the timing to eliminate pinging...

Long story short... regular is fine...

 

Use what it says or higher, but not lower.

This is also the 2005 and up section and I see you have a 2001 which may have a different requirement than us.

I was always under the impression that GTs needed premium and I was surprised that this 2006 of mine called for 87. I guess premium is what they needed a long time ago but not any more due to knock sensors and such.

 

Check your Owners Manual. It's possible that your 2001 MAY INDEED need premium but since this is the '05 and up (S197) forum, I really wouldn't know. The S197's only require 87 octane.

 

Pretty sure the 2V 4.6 GT's took 87.
Now the 4V 4.6 Cobra may be different story

 

i dont have a owners manual,so i downloaded one,and it says to run at least 87 octane.

 

Yes the 2v's take 87 and the 4v premium

 

that had me worried because when i took the car for a test ride i did not notice it says premium on the speedometer,till i bought the car,but cant figure why it says premium when the owners manual says regular?