Premium or?

[Vaca2097]

Okay so I picked up an 04 gt to replace my 98 that an idiot plow driver wiped out over the winter. Problem is that the previous owner said he's running it on premium because the owner before him had it tuned. But I don't have the tuner (if it was a canned tune) or any indication that it needs premium. My only hint as to anything being done to the ecu is that the rear 02s were shut off as it doesn't have mil eliminators and it doesn't have rear cats. The only obvious mods are a kn intake, dragon plenum, catless x pipe, and Flowmaster cat back. The rest are visual and suspension.

So what is the most cost effective way of figuring out if it's been tuned and needs premium? I do have the torque app if that helps.

 

[BigBore96]

Put whatever gas in it you want.

Most likely the "premium" tune was a bs canned tune that is just a drop down on a handheld tuner.

As far as cost effective? Put some regular in it. Beat on it some and see if it pings then check your plugs either way.
My money would be you won't notice a difference regardless.

 

[ttocs]

if it had the mods necessary that it needed premium I don't think there would be a question that work was done to it. As he said though put regular gas in it and if its pinging them use higher octane. Check out around the passenger kick panel/glove box and see if you can find an itty bitty little selectible switch.

 

[96blak54]

Gonna need at least 11.1static compression to fully utilize premium gas.

 

[Vaca2097]

I could not find a switch near the glove. It's full of premium so I'll run the tank low and refill with regular. I understand about higher compression or mods that necessitate premium. But would advancing timing through a tune require it? If I eventually buy a tuner to put a known canned tune on it would it need to be reflashed to stock for that to work? Sorry, my knowledge beyond bolt on is lacking

 

[96blak54]

Yes, a tuner advancing the timing and leaning out the mix could cause a problem with low octane fuel. Dont fret it tho. If the low octane does cause a problem, youll only notice the problem in the higher rpm when making pulls. Im 90% positive normal driving wont be affected. So, take a chance, see what happens.

With that said, my 13.1static compression is tuned for 93octane back when the compression was 9.1. Ive tested 89octane just to check how it responds.....well, it doesnt like it! Although i could drive the car normal with no problems.