n/a_threat

It is just a waste like the rest of the guys said. There would be no negative effects on the engine. All octane ratings are is the point to which it combusts. Higher compression motors for example need a higher octane to prevent detonation.

djdalfaro

so in your opinion (I know I'll have to double check on my own), can I downgrade to 89?

~Alf

n/a_threat

Before gas got to $3 a gallon I would always run 93, even though I didn't need to. (I just wanted to put the best in my car)

But I've just downgraded to 89 and the car runs just the same. Over the next few months I'll probably try 87 as well. But most of the guys on the forum use 87 unless they have f/i or are spraying.

Dave2000GT

You'd probably lose a tiny bit of power on top of it being a waste of money

Deannostang

If your Predator tune has advanced the timing all the way, then your "minimum" octane requirement will be 91. High octance pump gas ranges between 91 and 93 depending on the brand. You have essentially recalibrated your engine tune for premium with the Predator. The Predator does offer a lower octane rating tune if you go back into your computer's head and make the change. Then you can buy lower octane fuel.

djdalfaro

eh... i'll stick with the 91... now to see if the fuel station on my base can order it cheap for me??

GTnAZ

Quick question about 87 fuel... i run 87 from costco and when i have my A/C on my car has that 'ping' sound to it... would 91octane clear that up?

GTnAZ

bump for help!

Monch

if it were pinging, then yes. fill it up with 89 next time your at the pump, if the problem is solved your're done. but when does it ping, under heavy load (wot) at 4000+ rpm? or lower, if its lower and your car is basically stock, you have a problem.

GTnAZ

yeah its anywhere from 1500rpm to 3000rpm only under load with the A/C on. If the A/C is off there is no nosie at all. Im pretty sure there is no problem.. a lot of cars do it around here with the low octane gas and heat.. its already hitting 97-98 degreese here in southern AZ.