91 octane?

[2010TRDtaco]

Only use what your owners manual says, higher octane in a vehical not made for it will cause a build up in the combustion chamber and will eventually make the engine knock

[1TUFFTRD]

In my 2005 manual it says for best performance use 91

[whippersnapper02]

Originally Posted by 1TUFFTRD

In my 2005 manual it says for best performance use 91

Not anymore.

[lmikk12]

Originally Posted by whippersnapper02

In some cases it can cause a power loss that's why not. Back in 2000ish when I used to subscribe to Sport Compact Car they tested a new Honda Accord V6 on 91 octane and they lost an average of 10 horsepower on the dyno runs. The car only called for 87 octane.

Really, did it say why? i have never heard of anything like that.

[lmikk12]

Originally Posted by 2010TRDtaco

Only use what your owners manual says, higher octane in a vehical not made for it will cause a build up in the combustion chamber and will eventually make the engine knock

I can see what you are trying to say but but carbon deposits are not cause by higher octane fuel they are either caused by a rich air/fuel ratio or oil consumption. but over time carbon deposits can make you vehicle knock.

[1TUFFTRD]

Originally Posted by whippersnapper02

Not anymore.

That's why I said my 2005

[whippersnapper02]

Originally Posted by lmikk12

Really, did it say why? i have never heard of anything like that.

The fuel was harder for the engine to ignite.

[lmikk12]

Originally Posted by whippersnapper02

The fuel was harder for the engine to ignite.

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

[whippersnapper02]

Originally Posted by lmikk12

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

Well you said it yourself. The higher octane fuel resists ignition. Well in an engine that requires less octane the cylinder pressures probably aren't high enough to ignite the high octane fuel easily.

[lmikk12]

Originally Posted by whippersnapper02

Well you said it yourself. The higher octane fuel resists ignition. Well in an engine that requires less octane the cylinder pressures probably aren't high enough to ignite the high octane fuel easily.

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

[KenLyns]

Originally Posted by adam2180

I have always used it because I have been told its cleaner gas.

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.

[whippersnapper02]

Originally Posted by lmikk12

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

Yeah but if you ignite straight gas on the ground it won't explode. Compress it and it will make a powerful explosion that will drive a piston down.

[Tacomanator]

Originally Posted by lmikk12

Really, did it say why? i have never heard of anything like that.

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.

[lmikk12]

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.

[2010TRDtaco]

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"

[JDCPA]

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.

[lmikk12]

Originally Posted by 2010TRDtaco

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"

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.