I've been using mid-grade gas on my stock GT. I just recently started using regular octane because gas prices are ridiculous. I probably shouldn't be worried, but if I did accumulate any build-up in my engine should I use one of those bottles of engine treatment/fuel line cleaner next time I fill up? If so which brand/type should I use? Thanks!

Also, I just sent pics of my car to Amanda to post in the member's gallery. Check em out out. They should be up soon if I submitted them correctly. On top of the usual performance upgrades, I plan on putting red racing stripes on it. That 3D Carbon body kit also tickled my fancy (minus the rear spoiler). Maybe $omeday...

 

chevron already has techron in it, and is listed as one of the top fuels,
My brother who has been a ASE Master technician for over 25 years recomends it highly
need I say more?

 

If your Mustang engine is still stock it might make sense to stick with what the manufacturer says. 87 octane should be fine.

 

I wouldn't be putting any kind of treatment in your tank unless you have a problem with some water in there or something. If it aint broke, don't fix it.