Blacksmoke

I was talking to someone interested in buying a GT500 but was concerned because they only had up to 90 octane gasoline where they lived.

I told him I would NOT run 90 all the time since it is tuned for 91.
I have always heard not only could it affect performance, but that it would damage the engine. Especially over time. I tried to explain the rich/lean factors when it comes to engines.

Someone else joined the conversation and seemed to think
I was silly and 90 was fine.

I don't mind being wrong at all. Learn something new that way.
But from my understanding I have always gone by that.

Am I wrong or would running 90 octane eventually damage the engine?
Remember this person was asking about ALWAYS using 90 octane.

99GTvert

..though I don't have info on hand to back it up, I think the one point does make a difference.

Do you know if that gt500 is local to that buyer? They could ask the owner then if it pings at all.

Blacksmoke

The owner claims he has run his on 90 for a year.
I asked him about pinging but yet to have a response.

I have heard of one point differences causing ping MANY times.
But I don't know if running the lower oct. will DEFINITELY damage the engine over time.

I just don't want the guy considering buying, or that other guy to be doing something
that is going to damage their engines.

MarkMan

I wouldn't do it. But it all depends on the tune. I would think that a custom tune (Brenspeed or AM/Bama, etc) would be iffy, and I would not run the car all out with one of those. With a canned tune it probably wouldn't matter since they are intended to cover a wider range of situations. With a dyno tune I definitely would not run anything lower than the tune specified. That's just my opinion tho!

Blacksmoke

This would be on a stock tune.

MarkMan

I still wouldn't do it, but it probably won't hurt anything, especially if not driven hard (the way we all do, that's why we have GT500's). The difference in performance with my AM/Bama tune and the stock tune makes me think that it probably won't hurt, but Ford says not to use less than 91 octane so I gotta go with that! BTW I can only get 91 octane here in NW Arkansas and I run the 91 race tune all the time.

05 Mustang

It should be just fine. As long as they are running the highest octane available, they shouldn't have any problem.

If you think about it, stock GT500's sell everywhere. The dealers are not retuning or recalibrating them.

JMO

Dogman4

I would still be cautious about most fuel stations because of the additives/lack of and watch for too much ethanal. In my area there are no BP stations (one recommended) so I've used Chevron. My son is a tech for a local dealer and said it's the best in the area.

Dogman4/Users/stevendow/Pictures/iPhoto Library/Originals/2011/2009 Cobra/IMG_0307.JPG

Riptide

Probably won't ever damage the engine.

If they stay out of boost.