What is the recommended gas grade?

89 oct or 92 oct.

my sister in-laws recommends regular. what does the owners manual say?

i run 101 in my car but it is to expensive the only reason i run it is i work at sunocco and its cheap for me to get it it runs cleaner and the motor dont gum up as bad

2003 GT...actualy these days even bronze is prety good but depands on many factors my friend. Is it an every day car,do you have a heavy foot? Mid grade should be good enough but if you want a cleaner burn and performance of course the high grade is better. Now days it`s all about price. But higher grade burns better,cleaner and performs better for all cars. Unless your engin is not stock then ya might be better off with the high grade of course.

I have a 07 Mustang GT, yes i know its a different motor/carm, but i run 93 octane from BP or Texaco. On a dyno when i had like Circle K gas in it, i got 293 horses to the wheels and 310 torque and then they told me to take it to bp across the street and fill it with bp then i got 296 horses and 316 torque. But it matters to you if your going to be on that pedal with a heavy foot or if your just going to drive it normal. I would recommend Premium(93 octane) or at least mid-grade (91 octane)

push the regular button fill her up... unless you superchip her set it up for performance endurance and then save money buying premium... i dont wanna hear haters ive done the math...

If you're going for max horsepower and performance, 93 Octane is what I use and it noticeably increased performance. If you would like to test it, burn up all the current fuel and fill it up with 93oct. It will work best if the car have significant upgrades.

You should be ok with regular but the biggest thing is to stay away from ethanol enriched gasoline. I dont care if its cheaper or not. The stuff saps mileage and gums up injectors. If the premium was verified to have no ethanol in it, I would buy that for sure.

unless u have a supercharger or turbos just run regular the high octain wont make the car perform any better.....they are designed to run their best on the lower stuff i have a 94 5.0 and i have only put the 83 or w/e it is in it and it runs just fine

Depends on how you have your engine tuned. If you are running a high performance timing or have a high flow air intake and plenum, I would definitely use 92 octane or higher. For a stock engine use 87 or 89 octane and change the oil every 3000 miles like the owners manual says.

gas

My 2014 GT 6-speed at sea level performs without any issues on regular. Only upgrade cold-air intake. It's not raced, but driven hard where I can get away with it. If I change exhaust and tune, I'd switch to premium

I have a 2000 gt and I put regular but people tell me to put 93 but I haven’t done anything to my car I’m just confused

You have to remember . Ethanol is used to up the octane. If you find 93 octane it might have ethanol in it to boost the octane. That being said.. Ethanol will not , I repeat Not gum up your injectors . As a matter of fact you can change your injectors for more fuel to get E 85 and get another 50 horses out of your 5.0 mustang.. Thoughts?