91 octane?

Hmm, never heard of that its not jet fuel,haha

 

Yes but thats what the spark is for, it isn't a diesel either.

 

Cleanliness is the same. 91 may have more additives, but it's up to each fuel brand. In some areas, Shell 91 is listed on the pump as ethanol-free while 89 and 87 contain up to 10% ethanol.

 

It's like trying to put 100 octane race gas in a stock 4 stroke that only calls for 91. Like whipper said - harder to ignite.

 

race fuel vs. 91 octane = two separate things, i know that race fuel burns hotter and with more power on explosion.....and so does our old snow blower....hahah all i said what that 91 is what i put in my car/truck to prevent detonation or preignition, that will have undesireable effects. i never said to run you truck on race fuel, and actually i accidently put 100 octane in my truck and it ran fine but i was worried about my cat. conv. because race fuel contains lead. im not talking about putting in c12 or jp40 you guys, but i dont want to get off on a tangent, next time you talk to the most knowledgeable person you know automotive wise ask them if running 91 is bad i think you will be surprised at there response.

 

Imike12
I kind of see what your thinking but your wrong. You don't know what your talking about. Let me school you a lil bit, no charge.
91 octane burns slower, so it leaves behind unburned residue in the combustion chamber, which causes a carbon build up, after period of doing this it will cause a knock on the compression stroke "piston goes up"

 

My boat mechanic tells me not to run 91 octane in my Mercury outboard. He went into a (rahter long) technical explanation that ended up noting that the engine will actually put out less power than with lower octane fuels because it is optimized for the lower octane and is not as efficient using higher octane fuel.

The 2.7 is optimized for 87 octane and you are doing nothing but wasting money burning anything higher.

That doesn't mean the quality of the fuel doesn't matter. I don't run anything but Shell in my 5 lug because its additives are present even in the ower octanes.

 

Ok cool to know, thanks for the info, i was going off of what the best mechanic i have ever met had told me so i had no doubts, when you described it does make sense now. learn something new everyday.