Octane Boost - Anything Wrong with Using??
As long as it doesn't contain lead ot MMT, it's not a problem. You can get away with MMT for a while, but lead (TEL) is a definite no-no.
Advanced
Joined: Sep 2008
Posts: 54
Likes: 0
From: South Western Pennsylvania
One thing to keep in mind is that lower octane fuels burn faster and hotter and have a lower flash point than higher octane fuels. In a hot engine, this can lead to preignition which causes the pinging and knocking sounds and can cause damage to the engine. Just something to think about if you're running your air cooled Harley in high temps while in traffic. 
Only reason HD says to use 91 octane is because they tune the engines lean from the factory and don't want any pre detonation problems. If you have a dyno tune or a stage 1 down load or a PCIII or equivalent, you will be fine. Ultimately you should listen for pining, but chances are you wont have any in your really low 9.5 to 1 compression HD that has a minimal timing advance.
Tourer
Joined: Dec 2007
Posts: 426
Likes: 0
From: On the road to nowhere, UK
Low octane fuel will be perfectly ok in both 88 & 96 engines. Under high engine loads or high temperature continous running you may hear the pre-detonation 'pinking' noise (which actualy sounds like something metallic is occasionaly tinkling on the tarmac), but it won't damage engines unless it's over a very long running time.
I came over the Pyrannees last year and heard it pinking on the up grades, but after a coffee stop it was ok again & no harm done.
The O2 sensors will actually work in your favour with low octane fuels as it feeds back to the ECU about what's happening in the exhaust and adjusts the ignition and injectors accordingly, so despite all the complications, EFI actually comes into its own in these situations certainly better than a carburetted engine.
The bottom line is low octane fuel is fine unless you're working the engine hard or long.
And don't even think of using Toluene - it's highly carcinogenic.
I came over the Pyrannees last year and heard it pinking on the up grades, but after a coffee stop it was ok again & no harm done.
The O2 sensors will actually work in your favour with low octane fuels as it feeds back to the ECU about what's happening in the exhaust and adjusts the ignition and injectors accordingly, so despite all the complications, EFI actually comes into its own in these situations certainly better than a carburetted engine.
The bottom line is low octane fuel is fine unless you're working the engine hard or long.
And don't even think of using Toluene - it's highly carcinogenic.
Road Master
Joined: Aug 2008
Posts: 990
Likes: 3
From: lakeside ca.
I have run mid grade for most of my 04's life and on occasion regular no problems just have to shift a little more and not lig the engine but then they put the trans in for a reason you just need to use it..oh I have 42 thou on the clock..
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Stellar HDF Member
Joined: Feb 2006
Posts: 2,501
Likes: 410
From: South Florida
I use the HD fuel additive. Works good for me, but I run 93 down here. Have to, because it's hot most of the year. If it's coller outside, it won't pooch the motor. Used to do it all the time in the evos come winter. They actually ran better.
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