Gas Question: Premium vs. 100% Regular

Given that 10% ethanol gas is probably doing long term damage to my 2005 ST1300,

and

Given that the engineers at Honda instruct me via the owners manual to burn premium gas in my bike,

and

Given that the only local station offering 100% gas only offers it in 87 octane,

Am I better off running premium gas that is 10% ethanol or 87 octane that is 100% gas? Which is worse in the long run for my ST? Discuss.

Interesting question......I'd like to know the definitive answer to that one myself.

The main difference between 87 & 93 octane are the flashpoints. The lower octane gas will ignite easier because it has a lower flashpoint. Because it ignites easier, it can ignite prematurely in our ST1300 engines ... AKA pre-ignition ... more commonly known as engine knock. A continuous pre-ignition condition will slowly destroy your main and rod bearings. How much damage does 10% ethanol cause? I don't know, but if it's all in the fuel delivery system, I suspect the damage from ethanol is less costly to repair than rebuilding the bottom end.

I have the definitive answer. From previous discussions on the site it has been unaminously determined you should, don't worry just go ride. It's been more than proved either or way is fine.

I don't know of any post ever that has said anyone has had damage from running the "wrong" grade, blend or brand of fuel. Oh I should say, I don't think anyone has been running the 85% alcohol.

83,000 miles of whatever blend of "regular" the station pump has in my bike. Lots of 5 or 10% "regular" ethanol through my bike as sometimes there wasn't any choice.

Raymond

I too wonder a little bit about this given that Colorado runs 10% E during winter months....but nothing I can do about it.

I give priority to first ensure I'm putting in 91+ octane (I'd choose 91 octane with 10% E over 87 octane with 0% E).

Whether or not the fuel contains 10% E or not is beyond my control. As I look at it perhaps 10%E does bad things to the fuel system (or makes it hard to start after sitting for weeks), but predetonition from low octane does bad things to the engine.

I've just not found I had the choice of 10%E at one station and NOT 10%E at anther nearby station ... I fill up with 91+ octane where I stop without looking for a non-ethanol station

Question 1 - Won't the knock sensor diddle (scientific term) with the timing to minimize, reduce, eliminate knocking, no matter what grade fuel I run?

Question 2 - If the Honda engineers know so much about fuel and oil, how come they know so little about seats and windscreens?

Fred D said:

Question 1 - Won't the knock sensor diddle (scientific term) with the timing to minimize, reduce, eliminate knocking, no matter what grade fuel I run?

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Not eliminate, maybe reduce. I have heard my engine pre-ignite on occasion while running high octane. I do not understand why the engine management system allows this.

Fred D said:

Question 2 - If the Honda engineers know so much about fuel and oil, how come they know so little about seats and windscreens?

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Engineering mechanical items is simple in that there are finite aspects in which to apply values, measure, target and achieve. How does one engineer a saddle and windscreen to suit everyone's arse, height and personal preference?

I wouldn't be worried about the bottom end but would be worried about the head/valves/piston because of the over temp of an exploding fuel mix rather than a proper burn. I think Fred D's #2 question was tongue in cheek.

W0QNX said:

I don't know of any post ever that has said anyone has had damage from running the "wrong" grade, blend or brand of fuel. Oh I should say, I don't think anyone has been running the 85% alcohol.

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Ray.. remember the couple of guys that had stuck open valves after long trips thru e85 country?... It was thought that that MAY have been the reason... mixed tanks ? who knows but thats the only damage I've heard of from wrong grade.

I just know Ive run a few tanks of lower grade pure gas and low grade with 10% alcohol and the pure gas runs better for me. But if Higrade is called for, its not too much diff in cost.
Another answer may be to just throw in a good dose of Seafoam now and then.

Tom

What about running mid-grade? or Half and Half?

I have always run premium though have thought about when on half tank fill up with mid grade to save a few bucks

Greg

You might save ( here .10 diff from mid to hi test ) $.30 on 3 gallons.... not even enough for a water

hoowasat said:

The main difference between 87 & 93 octane are the flashpoints. The lower octane gas will ignite easier because it has a lower flashpoint. Because it ignites easier, it can ignite prematurely in our ST1300 engines ... AKA pre-ignition ... more commonly known as engine knock. A continuous pre-ignition condition will slowly destroy your main and rod bearings. How much damage does 10% ethanol cause? I don't know, but if it's all in the fuel delivery system, I suspect the damage from ethanol is less costly to repair than rebuilding the bottom end.

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+1 one of the few posts on this subject over the years that got it right. I have been saying this for years. As I have pointed out before, this is more of an issue if you live at sea level and in a cold climate. That is when and where the air is the most dense. At high altitude and in the summer you will have less issues with running 87 oct as the air is thinner and it isn't heated as much in the compression process. As proof that hot air can cause fuel to ignite, just look at how a diesel engine works. There are no spark plugs. It compresses the air which causes it to heat up enough to ignite the fuel air mix. Granted diesel engines have way more compression than gas. Diesels are typically around 19:1 where the ST1300 is 10.8:1. However the flash point much higher in diesel fuel compared to gas.

Personally I have run non-oxygenated super premium. The gas station that I ride by twice a day when commuting and that is 5 miles from the house just so happened to have non-oxygenated fuel in their super premium tanks. I say had because I don't know what they have now. I noticed last week they changed their signs they used to be a Marathon station and now are a Holiday. Around here all the Marathons had no ethanol in their super premium. Holiday stations how ever carry E10 in all the pumps. I haven't had to fill up there lately so I don't know if they will still have the good stuff. This time of year I am burning Diesel as my winter beater is a VW Jetta TDI. Those pumps are not near the gas pumps.

For me I have burned both. I do run super in both bikes. The 1300 requires it and it gets better gas mileage on it. It also has a bit more power based on my butt dyno. I do use E10 from time to time mainly when on trips. I will take super (E10 or not) over running 87 or midgrade. As for damage running E10. I haven't seen any post here or any other form where Ethanol has been identified as a source of damage on a 1300. The only issue fuel related has to do with carbon buildup in the valve guides. If this happens the bike will not run right and have 0 compression on one or more cylinders. This technically doesn't break anything and the engines have been returned to life by running additives to clean out the carbon deposits. We don't know if Ethanol is the cause but there have only been a handful of cases and there are way more people out there that only run E10 because that is all they have access to. So does E10 scare me, nope.

I will point out that on the 1100 I personally think that the reason the fuel cutoff is such a problem is because of E10. One problem with ethanol is that it will degrade rubber if it isn't designed to resist the effects of the alcohol. Well the problem people have is that there is a rubber diaphragm in the cutoff that is vacuum operated. It is also in contact with the fuel. We don't know if it is or isn't failing because of the fuel. It could be partly due to age but the fact that the number of failures have gone up as E10 became the norm. Also people have replaced them only to have them fail again. This would lead me to believe that it is more than an age issue. There is a well documented process to bypass it so it isn't an issue once that is done. Again this is the only part that I know of that some of us think are prone to damaged by the ethanol on any model ST. There is nothing on the 1300 that I have ever read about. It is only something on the 1100.

LOL, I'm a stubborn old coot. Proselytizing and :bow1: to "Mother Honda" has done little to change my opinions. .

Or, as we say in the home-brewing world RDWHAB - Relax Don't Worry, Have a Home Brew .

I'd have to believe it's really mid grade or high grade in the station tanks before I'd buy other than regular regularly.

Raymond (me=paranoid crazy loco)

ok here's a long shot for most locations but in my area there are three stations. If you have a smart phone download the app..."ethanol free gas finder" and you will get real gas stations. At my local sunoco station the gas is 90 octane and costs 4.23 a gallon. Because of where I live in Florida I can even buy Av Gas because the airboats use it. Although it is labeled for recreation use at the pump you can consider your bike a recreational vehicle...I do!

Be aware that Av-Gas contains lead and has more lead than leaded auto-gas

Aces Gadget said:

Be aware that Av-Gas contains lead and has more lead than leaded auto-gas

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Great point...thanks

I run 93 of brand name gas and about every 4 or 5 tanks run a good dose of ethanol formula Marine StaBil through the tank to move along any water and decarbon the combustion chambers. In this area we have had 10% ethanol for several years. There are four major wholesale distributors of gasoline and the last of them went E10 then. It is difficult but not impossible to find 87 without E10 but not non-E10 midgrade or premium. Whatever, at 104,324 miles my bike still does not burn any oil and tops out at 150 indicated and 142 on the GPS. It used to top at 141 but the last few thousand miles it just seems run a little bit stronger. I guess it is finally broken in.

Leaded gas is not bad for valves. Tetraethyl lead is actually good for valves and valve seats. The problem with it is that it will destroy the effectiveness of catalytic convertors. That is why it was phased out of auto gas in the mid seventies when CC were introduced to help control emissions.

hoowasat said:

The main difference between 87 & 93 octane are the flashpoints. The lower octane gas will ignite easier because it has a lower flashpoint. Because it ignites easier, it can ignite prematurely in our ST1300 engines ... AKA pre-ignition ... more commonly known as engine knock. A continuous pre-ignition condition will slowly destroy your main and rod bearings. How much damage does 10% ethanol cause? I don't know, but if it's all in the fuel delivery system, I suspect the damage from ethanol is less costly to repair than rebuilding the bottom end.

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I think you may have some terms confused. The octane rating of fuel only applies to how much it can be compressed before spontaneously igniting. The higher the octane the more it can be compressed. It has no bearing on the flashpoint or how easily it ignites.

When a fuel of too low octane is used it causes detonation. Detonation and Pre-ignition are similar but not the same. Pre-ignition is caused by something in the combustion chamber being too hot and ignition occurs before the spark plug fires. This can be a sharp burr or too hot of a spark plug. Pre-ignition can and will be caused with all grades of fuels.

For the few that don't have smart phones, you can go directly to the ethanol-free web site to find stations listed by state and city. Here's a link. http://pure-gas.org/index.jsp