03sonicgt

Hey guys, I have an 03 GT with an xpipe, flowmaster 40's, udp, cai, and a maf. I've been putting in 93 octane for about a month because gas is lowering around here in Michigan. Should I be using premium right now or not? Any disadvantages for using premium? Thanks - Kyle

Aixtreme89

Unless you have advanced your timing or you have higher compression than stock there is no need for you to use higher octane than 87. If you use a higher octane like 93 you actually losing performance, your motor the way it is now, can not burn the gas as effieciently as the 87 octane. Using 93 your not getting a complete burn and probably getting lower performance and worse fuel economy because of it. I dont think it has any harmful effects on your motor. But lossing fuel ecconomy and performance is enough ensentive to not use an octane more or less than 87, for the set up you have now. Once you get a handheld programer and advance your timing then you will need to use a higher octane gas, but you will also see a performance gain because of it too.

03sonicgt

By advancing your timing, what do you mean exactly?

Matts00GT

He means if you have used a handheld tuner or timing adjuster. Which you havent or you would have listed it. You are wasting 20 cents a gallon right now. Use regular.

03sonicgt

Alright guys, on my cars gauges, its says premium unleaded gas only? Does that mean anything? I know I sound like a moron, I am just a little bit confused. They are after market white faced gauges. Boy I sure wish I would have known exactly what the guy did to the car before me.

Matts00GT

Check your owners manual. It will say to use 87 octane. After market gauges wont know what you need.

03sonicgt

Thats what I figured, so 87 octane for now, but once I get it dyno tuned(this spring) change to 91/93?

Matts00GT

Not necessarily. More than likely yes, because he will mess with the timing. He might advise you to use a flip chip. Then you would use a stock tune which would keep it at 87 and then a perf. tune that would require higher octane. For now stay with 87 so you can save some money up to afford the dyno tune.

sprostang

You probly have a guage cluster for a cobra, or maybe just the overlay. If so, cobras 03-04 are S/C and require premium. GT`s do not when they are stock. Thats where the confusion is.

Tim37

there is a huge diffence when it comes to gasmilage i get about 30 more miles per tank on 93 over 87