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Just run the lowest octane locally available. I've run 85 in the western mountains with good results even when pulling a trailer.
 

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So now that we all know lowest grade is best.is there a better station to buy from or a worst to buy from?
 

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Ecellent Article. Tank you!

What octane Gas should I use?
How to “Get Gas” without leaving skidmarks

by: Brian "Tapper" Davis

One of the most frequently misunderstood issues among the VTX community, and indeed among all folks concerned with performance and appropriate care and feeding of their motors is the subject of gasoline, and more specifically the mysterious octane number. Oil companies have gone a long way to foster this mystery, by marketing gasoline with higher octane numbers as “premium”, and inferring that the golden road to more performance, cleaner widgets, and hot chicks, is to spend the extra dough on the higher-octane stuff. Well, sorry to be the one to break this to you, but you’ve been had. So lets take a quick look at octane, and then get to the big point – what should you run in your VTX?

Now the truth is, octane is actually a chemical, which comprises an important part of the chemical soup that is gasoline. But here’s the thing – octane the chemical has absolutely nothing to do, with “octane” the pump measurement. So what is it?

In a nutshell, the octane rating of a fuel is a measure of its ability to resist detonation, ping, pre-ignition, or knock. The number we most often associate with octane is the "Anti-Knock Index", or the "Pump Octane" number. This rating is an average of two different measurements - the Motor Octane Number, and the Research Octane Number. Both of these measurements are taken using a special single cylinder test engine that has a variable compression ratio. The RON measures the knock resistance of a fuel during low RPM, light load conditions, while the MON is representative of high-speed, high load operation. As a result the MON will always be lower than the RON, but for our purposes the Research Octane Number is more significant because it more closely represents the way a low rpm V-twin motor is operated. So “Octane”, has absolutely nothing to do with the energy content or quality of gasoline. It’s just a measurement of when the gas will make a motor of a specific configuration begin to knock.

Lets take a moment here to define a couple of things important to understanding this discussion.

Knocking (also called pinking or pinging) in internal combustion engines occurs when fuel in the cylinder is ignited by the firing of the spark plug but burns too quickly, combusting completely before the optimum moment during the compression phase of the four-stroke cycle. The resulting shockwave collides with the rising piston, creating a characteristic metallic "pinging" sound. The fuel is normally ignited slightly before the point of maximum compression (the spark advance) to allow a small time for the flame front of the burning fuel to expand throughout the mixture, so that maximum pressure occurs at the point of maximum compression. It is only when this flame front arrives too early, for whatever reason, that the knocking effect occurs. If allowed to persist, knocking can cause vibration and damage to engine parts.

Knocking is a different phenomenon from pre-ignition, which occurs when the air-fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is caused by heat buildup in engine components or overheating of the air-fuel mixture during compression, and cannot be prevented by delaying spark plug firing. As such, if pre-ignition is allowed to continue for any length of time, severe engine damage can result. Pre-ignition is bad bad stuff, and changing the octane of the gas won’t affect it.

Generally speaking, a higher-octane gasoline prevents knocking by either slowing the burn rate of the gas, or by increasing the difficulty of lighting it up. The idea here is to prevent the gas from burning too fast, and causing knocking. So the octane number has no bearing on the quality of the gas. But it does have a bearing, on how well your motor can utilize the gas and extract the maximum energy from it. However, getting too far into details of this would require a pretty damn big article, so I’m going to generalize a bit, for the sake of brevity here.

First, consider that gas burns faster under pressure. The more pressure, the faster it burns. Therefore, a high compression motor will burn gas faster than a low compression motor. The VTX is a relatively low compression motor folks. So, we don’t really want a slow burning gas.

Second, the burn timing in your motor is hugely important when considering how well the motor can develop power from a given amount of gas, and this timing is determined by the ECU, which can manipulate the spark advance of your engine. Normally, the timing in your VTX is pretty close to 8 degrees before top dead center, but the ECU can and does retard or advance the spark timing to respond to certain running conditions of the motor, like coolant temperature, rate of increase of Rpm’s, or any of a number of other conditions. But none of these parameters are accessible (yet) by you, the itinerant tuner. So, you have no way to manipulate the spark to match the burn speed of your gas. Since the VTX is designed by the factory to use 87 octane gas, if you run something different, the only possible way you have to tune your motor to use a different octane, is to manipulate the compression ratio of your pistons.

So here’s the thing: Unless you have changed the pistons in your VTX, a higher octane gas will have the effect of de-tuning the motor, and therefore reduce its performance. Now, the amount will probably be minimal, but it’s there. That’s the meat and potatoes guys, but there are a few more things we can infer. First, at higher altitude your compression will be slightly lower, and therefore you can get away with running a slightly lower octane gas. In fact, in areas like Denver, where the altitude is up around 5,000 feet, you’ll find gas stations selling 85 octane gas. But you’ll never find a gas station in Texas selling 85 octane. Since the altitude is much lower, the octane rating needs to be a little higher, so regular gas is typically 87 octane.

Second, gasoline quality is dependant on a lot of things, but octane isn’t one of them. In fact, there is almost no real difference in “premium gas” other than the octane number. Federal law dictates the amount and type of most of the additives in gas. So by definition, they’re all pretty similar in nature.

Except.

Gasoline is formulated according to climate in the US, and gasoline refiners use 6 basic formulations based on the expected temperature in the area they are expected to be sold in. Gas companies vary this by season, and by location (it also tends to be colder in Denver than in Dallas). So that gas you bought in Dallas might not give you great performance in Denver.

These days, unleaded oxygenated gas is far superior in performance and energy characteristics as compared to the old leaded gas of yesteryear. We generally have very good gasoline available to us at the pump.

Lastly, just remember this simple rule of thumb: You should always use the octane rating recommended by the manufacturer for your motor. But, if you are riding in a climate significantly different than sea-level at 80 degrees Fahrenheit, then use the lowest octane gas you can find that will not cause your motor to knock.

One more thing – many cars these days have anti-knock sensors built into them (the VTX doesn’t), and those sensors are used by the ECU to manipulate the spark timing. So, if you run an octane significantly different from the manufacturers recommended octane number, the ECU will detune the motor in real time, and you won’t get any knocking – but you absolutely will lose performance. Use the recommended gas. If you’ve been running a higher octane gas, and spending the dough to do it, then I hope this little article will save you some bucks, and in the process gain you some performance. Good luck!
Last update: 2005-06-22 15:43
Author: Tapper
 

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Fill up early in the morning or late in the evening!
Never fill up when a tanker is filling the station!!
When they fill the tanks it stirs up all the stuff at the bottom
and comes out when you fill up.
NOT TRUE !!! the one filter at the filler hose on the pump will filter particulets down to about one micron . then you have another filter on your bike that will filter down just as good . there are very few steel tanks left in the U.S. . if the micro fine stuff DOES make it to your injector an then your cylinder , it will be burnt up . an then the detergant in the gas will do its cleaning . STOP FEARING THE OL' WIVES TAILS ! those are the warnings your dad told you about .
 

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I promised years back that I would not enter this discussion again. so I will just quote the book....

"unleaded gasoline, pump octane number 86 or higher"
repeat, "or higher."

Sounds like they are saying Please don't go lower than 86. I don't. I don't go anywhere near 86!

I don't wait 8,000 miles to change my oil.
I don't use Honda oil either, I use Amsoil, Mobil I, or T-6.
I use the Fram filter.
I love that bike and treat it well.
I also go to the florist for the old lady's roses and not $9.99 at Krogers because I love her too!!
Socks
 

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I promised years back that I would not enter this discussion again. so I will just quote the book....

"unleaded gasoline, pump octane number 86 or higher"
repeat, "or higher."

Sounds like they are saying Please don't go lower than 86. I don't. I don't go anywhere near 86!

I don't wait 8,000 miles to change my oil.
I don't use Honda oil either, I use Amsoil, Mobil I, or T-6.
I use the Fram filter.
I love that bike and treat it well.
I also go to the florist for the old lady's roses and not $9.99 at Krogers because I love her too!!
Socks
I'm sure the people you waste your money with appreciate your support.
 

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Discussion Starter · #68 ·
I'm sure the people you waste your money with appreciate your support.
:agree: Your bike isn't MADE to run on anything higher than the lowest grade. It has been PROVEN here MANY TIMES that premium makes the bike run poorer with lower mileage, lower power and fouling plugs. The VTX ECU can NOT change timing like a car/truck ECU does to make the higher octane work. It's just a waste
 

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I run the cheap stuff myself. But due to the ethanol messing up the carb on the weed eater and blower I now only run ethanol free gas for the small engines and the VTX. I do run a cleaner once a year. Check out http://pure-gas.org if you are looking for ethanol free gas in your area.
 

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NOT TRUE !!! the one filter at the filler hose on the pump will filter particulets down to about one micron . then you have another filter on your bike that will filter down just as good . there are very few steel tanks left in the U.S. . if the micro fine stuff DOES make it to your injector an then your cylinder , it will be burnt up . an then the detergant in the gas will do its cleaning . STOP FEARING THE OL' WIVES TAILS ! those are the warnings your dad told you about .
I hate to say this but it happened to me the other day on my way back from Laconia. I filled up at a Shell station and noticed the color of the gas was a lite tea color. Didn't think anything of it got about 30 miles down the road and the bike started to quite on me almost stalled when I was at a toll booth. On 95 south was cruising when all of a sudden she lacked power for a moment. It did this about 5 or 6 times scared the hell out of me hoping to make it home. I found that I had picked up some bad gas. Never ever had I had a tank of bad gas from Shell they are top tier gas. I fixed her by adding about 3 oz of Star-Tron gas additive and filling up at another Shell station in my local area that gas was clear. Have not had a problem since.
 

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I use Shell mostly but if not available Mobile or Exxon and add Star-Tron Sea Foam or Amsoil PI about 2 or 3 oz every week. That has keep me running smooth and clean since I've had the ride. Except once when getting a bad tank of gas from a Shell station.
 

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How much ethanol is bad?

I fill up at Petro Canada up here with 87 Octane.

On the pumps it states "may contain up to 10% ethanol".

I went to that http://pure-gas.org - the few I clicked on in Canada were all 91 Octane!


From Petro's web site:

Ethanol-blended gasoline is a fuel that typically contains up to 10% ethanol in unleaded gasoline. We use ethanol in our gasoline where legislation requires its use and where conditions warrant. The Federal Government has regulated that motor gasoline sold in Canada after Sept. 1, 2010 must contain an annual pool average of 5% ethanol. Different provincial mandates also exist, some with higher ethanol pool requirements. Because of these mandates, most grades of Petro-Canada fuel may now contain up to 10% ethanol. This represents a change from the previous state, where premium fuel was ethanol-free at Petro-Canada. To find out if ethanol-blended gasoline is sold at a station look for the yellow labels in the pump area indicating that the fuel may contain a maximum of 10% ethanol.
 

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Discussion Starter · #75 ·
15% ethanol and above will be bad for the VTX engines that were only designed to run on 10% blends. With e10, or 10% blends, the bike will run fine forever on it. It will have poorer mileage from ethanol, but the engine will be just fine
 

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I promised years back that I would not enter this discussion again. so I will just quote the book....

"unleaded gasoline, pump octane number 86 or higher"
repeat, "or higher."

Sounds like they are saying Please don't go lower than 86. I don't. I don't go anywhere near 86!

I don't wait 8,000 miles to change my oil.
I don't use Honda oil either, I use Amsoil, Mobil I, or T-6.
I use the Fram filter.
I love that bike and treat it well.
I also go to the florist for the old lady's roses and not $9.99 at Krogers because I love her too!!
Socks
Forget the octane numbers for a second. Using that fram filter on your bike would be more akin to slapping around your 'old lady' than buying her flowers.... :shock:

Just sayin'...
 

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I was wondering at that... you buy premium oil and the crappiest filter you can find? Why not the amsoil filter?

Premium isn't "premium"...it's a misnomer. It would be better called "more ignition inhibiting" but that's not very good marketing language to get you to buy something you don't need and in this case, shouldn't use.
 

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On a recent trip across the mountains up here in my 2010 5.4 L F-150, I bought Shell 87 Gas - I couldn't believe how much better the fuel economy was...normally, I'm like 13-14 liters/100 km, but with the Shell, I was down to 11!

So, when I got back home, I tried it 2 tank fills in a row with my VTX - whoa - she backfired like crazy...hard to start in the morning and after work...

I "wasted" money as some of you would say and filled her with a tank full of 91 Octane Petro Canada Gas - instant gratification - no back fire, and starts just like that.

Now, the 91 Octane has more "cleaning" agents in it up here, so maybe it was just bad gas from that Shell station?

I'm back on 87 from Petro Canada - she seems to run fine - but should I check my plugs? If they are dirty - replace them? I'm at 15,000 km's with the stock ones...
 

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Forget the octane numbers for a second. Using that fram filter on your bike would be more akin to slapping around your 'old lady' than buying her flowers.... :shock:

Just sayin'...
I'm glad you said it. I had to look twice at that one and scratch my head.:confused:
 

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Again, if you could adjust the timing of your VTX, yes you could benefit from high octane fuels. But you can't, so it won't do a darn thing for your VTX.
So, I just need some 93 octane and an adjustable timing knob like this, and I can get 25 more HP, right???


:twisted::twisted::twisted:
 
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