Pretty sure they suggest 89.

 

i think all the 89 octane gas where i live only contains 5% ethanol instead of the 10% that the 87 octanes. that may be similar everywhere which is why it was recommended to be used.

 

Wrong 87.
At least here in the States. For you Canadians, I have no idea.

 

I will have to check.


So, if it doesn't, is the additive not as effective?

 

89 is rec'd in the Hemi's, dunno about the 4.7's

 

Higher octane gas can only benefit with higher compression or timing changes that require it...Otherwise there is no benefit besides lightening the wallet quicker.... This is a common misconception that "premium" gas is somehow better for a regular engine built for 87 octane.. I have OCD friends who just cannot grasp this reality and waste thier money for no gain?
if fact in some cases like some motorcycles and jetskies and smaller engines, higher octane gas can be bad for the engine as it runs too hot I'm told.
BTW I dont know about gas in canada but here in new york state the pumps say 10% ethanol. I would think if there was only 5% in the premium they would certainly advertise it

 

wrong on the bike part. 90% of the bikes require 93 octane or better because they are capable of reaching high rpms.

 

I used a bottle of StarTron. I didn't see any difference aside from worse mileage. The last tank was infected with ethanol and I saw no change aside from gaining back my 1/2 mpg that I lost on the three previous tanks.
Today I put 20 gallons of pure 87 in my truck and it likes it. I normally have to run 89 octane to avoid spark knock when the gas is contaminated because of my tuner. I didn't get any knock on the 15 mile drive home after filling up.
I'm just going to use the other bottle of StarTron in my small engines.

 

generally, higher compression engines need higher octane.. all the octane compound is, is something that make it burn less readily.. such as water in gas would do.. but it obviously isn't water.. it's inert- just like NoS..

pre-det, aka pinging, on a higher compression engine is a really really bad thing..

my moto is 14:1 compression... there is no way anything less than 91 goes in it.. I once ran 87 because that's all there was.. not a good move.. I added a bottle of juice that raised the octane in whole rans, and poof- back to normal..

the hemi is a higher compression engine.. it doesn't have as much margin for error.. i don't know about the 4.7.. I do know this, and you gotta keep it in mind as well: there is a distinct difference between compression ratio and dynamic compression ratio.. compression ratio is based on stroke, deck, crush, bore.. dynamic figures the cam in there.. the cam closes the intake after the piston reaches bdc and has started back north.. how much stroke do you lose before the valve closes? THAT is dynamic compression..

i toss that in there, because- most engines don't and won't have an issue with 87 so long as there is no timing advance.. but, when the compression tightens up on them (say, north of 10:1), that advance striking too soon on a warm engine? something has got to give.. that is the reason, and the sole reason, octane is needed to be higher in performance engines.. it makes it harder to ignite.. and there ya go..

dynamic compression is ALWAYS less than mechanical compression.. there is margin to play with.. why risk it though?

anyway: I'm not seeing any benefits from startron right now.. dunno if it's winter gas, or other issues.. I know of a couple other issues I have, but they were there when I did see benefits from it.. so, I'm at a loss.. I'm still using it though, because I have another bottle and a half to go.. I'm blaming winter gas, and, just for the hell of it..

 

so does a jetski and I was told by the marina NOT to use high octane fuel...
I ride a cruiser so I dont know some sport bikes (sport bikes are not 90% of all bikes btw there's a lot of Harleys and metric cruisers out there..) likely have higher compression performance engines..just like some have radiators to keep the temps in check. my bike specs 87..

Again HIGHER COMPRESSION engines require it. As drew mentioned, usually 10:1 and higher... our rams do not have that compression ratio... they can ping with 87 octane because of other deviations from stock like timing changes from a tuner but they are designed to run with 87 octane fuel..thats why the so called death flash (which according to beekers dyno results is a whooping 4hp less than an sct tuners hp rating and a very similiar power curve) was created. it altered timing which was decided to be too extreme in certain situations
I'm assuming . 87 is not diluted weaker 93 octane gas it just have a different octane rating which is related to flashpoint and how quickly it burns I believe.... If I'm not mistaken diesel fuel has a higher octane than 93 and that wont run too well in a gasoline engine...
The point I was trying to make is if you have a stock engine (loud exhaust and cold air intakes arent real engine effecting mods when it comes to this...) and your engine says it requires 87 or higher octane fuel than running anything higher than 87 if you have no pinging, isnt going to benefit you... its not super gas... just a different octane for a different compression ratio situation.

here's some of what a quick google search brought up on the matter
http://autorepair.about.com/od/gener.../aa060504a.htm
http://www.ymhmotoboard.com/topic/ca...87-octane-fuel

BTW 4.7 is designed to run on regular 87 octane...
http://wjjeeps.com/ho_engine.htm