Gas octane

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mew905

New Member
Sep 24, 2012
647
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Moose Jaw
Just figured I'd see what others' experience was using different octanes of fuel. I usually use premium Shell V-Power (doesn't list octane, I think it's 91 or 93 though), and today I ran out of gas. I came home and there was a jerry can sitting out back for the lawn mowers full of gas. I assume it was 87 octane. So I poured out 1L, mixed in ~40ml of oil (for just under 32:1), and noticed some very, VERY obvious differences:

The negatives:
Throttle response was absolutely terrible, even at speed if I went WOT it would bog down for a second before speeding up, and takes several seconds to lower back to idle revs, this does not happen with the Shell V-Power, response is quick unless I'm at a complete stop and idling.
Noticably less power, it could barely haul me up the hill I ride up every day, and takes a long time to reach top speed, the V-power is able to haul me up the same hill at 35kph minimum, 87 octane it slowed to the point where I could have pedalled to help it along.
Idles rough

The strange:
My max revs is... way... way higher, though the vibrations get pretty rampant again, it was ridiculous how fast it would go. It simply did not four-stroke at all even going well above 65, the Shell V-power four-strokes around 61kph.

I want to hear other's experiences who have tried other octanes at preferably the same oil and ratio (some places dont offer different octanes so theres bound to be people who were forced into using a lower grade).
 

dodge dude94

New Member
Jun 8, 2012
1,017
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East Texas
I'm gonna point this out: you have a bunch of mods aimed at increasing power.
91-93 octane will help your engine out in that regard as it burns cleaner.

I personally use 89 as that's what our Echo equipment specifies, so we just buy 89 for the small engines.
 

mew905

New Member
Sep 24, 2012
647
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Moose Jaw
Any 4-stroking is not normal so don't blame it on the 91 fuel...
Actually 4-stroking is common (semi-normal) though not desirable. I noted it because it seemed strange that the only change was the gas octane and suddenly 4-stroking stopped. I researched what causes it and it would make sense 4-stroking occurs at the top of my rev range, but then the question is why would the lower octane stop it completely? I dont plan on running the lower octane because of the power loss but this is a rather odd case.
 

Ronzworld

Member
Feb 21, 2014
118
1
18
Regina,Saskatchewan
Only thing I can say too octane differences that is common would be the chance of detonation greatly decreases with the higher octane counts. That being said , the only octane boost product I found that actually does work ( and works well ) has been one made by Lucas ... tall red bottle , although it says on the back not for use w/2-stroke engines ... it seriouslly improves fuel values as well as when combined with Ams oil synthetic pre-mix runs so clean that the top of my pistyon still shines like it is new ! Zero carbon deposit !! Unbelievable ! My motor is a bit extreme too say the least along with a 5.2cc Fred head and dual HD Lightning ignition / CDI , twin NGK 8 's the normal pump fuels will barely run it with out serious detonation occuring , the mix ratio I use of the Lucas Octane Boost is full bottle into 12 liters of premium gasoline along with a 30ish:1 AMS full sythetic pre mix oil ratio and this runs my motor very , very well !! I am hard pressed ta say that the VP C12 race fuel performs any better at almost 2 1/2 times the cost .... So .. that being said ....
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