Low Compression #4 Cylinder

[HANKSXXX]

If running Premium makes you feel good.

Do it.

It's your money.

A few years back there was a test done in one of the magazines that took 3 high performance cars like the Corvette, Mustang GT and I can't remember the 3rd, which were supposed to run premium and drained it all out. They put enough regular gas in them to run each car 3 times down the quarter mile. Then they drained the gas again and put enough premium in for the same test runs. Interestingly the cars did run better times with the premium fuel. Now, you can run dirty fuel in a blackbird and no doubt it will run fine with it knock sensor there to adjust but for someone to say their bike runs like crap on premium while causing it to vibrate and such is just crazy. The sticker said 91 and I run 93. In 24,000 beautiful miles that bike has been flawless. In fact, I changed the plugs and to be frank didn't even need to because they looked that good. For the pennies it costs in difference and knowing how good things worked with slower burning fuel I'll stick with the good stuff.

Electronic engine controls are much more advanced in the cars you cite.

They will alter timing for different fuels in different RPM ranges.

The Blackbird has a knock sensor that tells you if the fuel isn't good enough.

Have you tried the lower grade fuel and heard spark knock?

If so, it needs the better fuel. If not, lower grade fuel is hurting nothing and in fact burns faster, generating more complete combustion and more HP/TQ.

[RodeRash]

A few years back there was a test done in one of the magazines that took 3 high performance cars like the Corvette, Mustang GT and I can't remember the 3rd, which were supposed to run premium and drained it all out. They put enough regular gas in them to run each car 3 times down the quarter mile. Then they drained the gas again and put enough premium in for the same test runs. Interestingly the cars did run better times with the premium fuel. Now, you can run dirty fuel in a blackbird and no doubt it will run fine with it knock sensor there to adjust but for someone to say their bike runs like crap on premium while causing it to vibrate and such is just crazy. The sticker said 91 and I run 93. In 24,000 beautiful miles that bike has been flawless. In fact, I changed the plugs and to be frank didn't even need to because they looked that good. For the pennies it costs in difference and knowing how good things worked with slower burning fuel I'll stick with the good stuff.

Whatever.

There are two ways of calculating Octane levels. RON (Research Octane Number) and MON (Motor Octane Number) A RON of 91 is roughly the same as a MON of 83.

Most pumps in the US list their Octane rating as an average of the two methods. (R+M)/2.

The owners manual says to use 91 RON

Doing the math...... (91+83)/2 = 87 (funny how that works out)

Unless you raised your compression ratio, or increased ignition timing, running premium fuel in your Blackbird does little but make you feel better.

[Para045]

Yeah I've tried 91RON ULP, 95RON PULP & 98RON Ultimate in my 98XX and found no real difference except the cost, one particular brand of 95 PULP does seem to give a whisker better economy and run slightly smoother but that is possibly just a coincidence I usually alternate between 91 and 95 depending on what is better value around the stations but don't bother with the 98 as all it does is lighten my wallet

[brianmacza]

Yeah I've tried 91RON ULP, 95RON PULP & 98RON Ultimate in my 98XX and found no real difference except the cost, one particular brand of 95 PULP does seem to give a whisker better economy and run slightly smoother but that is possibly just a coincidence I usually alternate between 91 and 95 depending on what is better value around the stations but don't bother with the 98 as all it does is lighten my wallet

My brother is a Chem Eng working for a little oil-from-coal company called Sasol. He states the the higher RON value fuels are heavier per volume (more dense) and thus provide more available energy to an average modern engine. I tested this for a while, and without changing my riding style, I got about 30km per tank better mileage on RON95 than the alternative RON93. The additional expense in my little 3rd world corner of Africa worked out pretty much the same ITO cost per kilometer, so I decided to use whatever was available as it made no discernable difference in terms of performance or feel.