Premium vs. Regular?

You may experience loss of performance, heavy spark knock (knocking from engine which robs power and may cause engine damage) and eventual engine damage if the heavy spark knock continues.

i know a person who run regular in a premium only sports car 1 tank 3 broken piston rods plus the other internal damage.

Also the worst part is along with what littlehorn and papa have said is that if there is damage, and there is a warranty on it, it will be void and you will be left holding the bill (my bro is a sevice manger (toyota/Lexus), and this has happened on a few FG's. but i do beleive that th 05 Acura has "spark enchancment" DON'T quote me on that, you will have to check your owners manual (if you dont have one, call a dealer). but you can run reg but the car will not preform as well as with what it was designed for. A friend at work has a 04 (he loves it) and he can run either, which is good seeing I live in Canada and gas is $1.10 a litre (or $4.20 a us gallon)

I agree with Ed, and his answer was why I was questioning on another forum where a guy said his Acura blew it's engine when he ran it for a few days on regular, and I'm thinking no way! The engine either had prior issues or the owner abused it while he was using regular, and I'm leaning towards it being an older engine that had prior issues before he started to use regular. Even back in day before there were computer managed cars I had cars that required premium and sometimes, due to financial reasons, I ran those cars on regular, and as long as I backed off on the throttle when they started to ping they were good to go; and even back in those days I heard cars with heavy pinging climbing long mountain grades in California and those engines didn't blow, and those cars back then didn't have the hardened valves like they do today. So I'm in the same school of thought that Ed is, running regular or middle grade fuel in a car that the manufacture says to use premium will be fine just buzzing around town as long as you're not doing any extreme full throttle driving, and even then with today's computer managed cars they will automatically adjust and retard the performance just enough to keep the engine from pinging, so I can't see any modern engine being damaged by using lower octane. Keep in mind though that some gasoline companies like Shell use their best fuel cleaning additives only in their premium fuels, so if you switch to a lower grade find a top tier gas that applies to their entire octane levels and not just premium. If you don't use a top tier gas then you will have to use a fuel cleaning additive maybe once every 3 to 6 months depending on how much you drive, and so far the best rated cleaner is probably Techron or Red Line which is probably(?) similar to Royal Purple Max .