I plan on switching to a higher octane in the Mustang. Do I flash the car at the gas station?.....or Fill up with new gas before?.....or Fill up with new gas after?

 

Get the higher octane in before you reflash.

 

<div class='quotetop'>QUOTE(don_w @ March 4, 2006, 11:12 AM) Quoted post</div><div class='quotemain'>
Get the higher octane in before you reflash.
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The CE light wont come on?

 

Running better gas than the car needs shouldn't be a problem. Running worse gas than the car is tuned for can be a problem.

 

Exactly. I've run premium through mine on one occasion (for some odd reason it was cheaper by $.04 than regular?!?!?!?). It did nothing any different than regular, but I swear the exhaust had a different smell to it

 

<div class='quotetop'>QUOTE(DaTT(1sK) @ March 4, 2006, 11:13 AM) Quoted post</div><div class='quotemain'>
The CE light wont come on?
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No not at all. When we had our little gas 'shortage' from Hurricane Katrina last year, several of the gas stations in my area ran out of regular, and I had to fill up on '93 octane. No problems - car ran great as always.