Weird Visual Fuel Test

[oneoldbanjo]

Just about a year ago I decided I would keep a sample of several different fuel mixes and see if I could find out how fuel ages. I mixed up several different types of gasoline and oil, and even put Stabil in one. I put the fuel mix in a plastic bottle and I drilled a small vent hole in the top so that it could breath and age like it would in a vented fuel tank. The newest fuel is the 110 Octane Torco racing fuel that I got from a local gas station that is near a drag strip on 8/22/08, the rest of the fuel is from March 2008. The bottles in the photograph from left to right are: Torco 110 Racing Fuel, Pump 89 w/Stabil, Pump 93, 11OLL Avgas w/Mobil 2t, Pump 89, 100LL Avgas, Pump 87 w/cheap Dino Oil mix.

None of the fuels look like they have degraded, and none of them smell funky yet. The 3rd from the right (93 Octane Pump gas) has lost a little volume and is the only one that has done so, as I put an equal amount of fuel in each one and marked the level so I could track evaporation. I have not moved the fuels around much and I don't see any settlement of the oil - however it may be that the dye has not settled out but the oil has.....it is hard to see oil that is the same color as the gas laying in the bottom of a dyed fuel mix. One thing I may not have done right in this experiment is that the fuel has been in my well insulated and heated garage, and the fuel has not been exposed to temperature extremes and humidity changes. My garage is 50 degrees in the winter and about 75 in the summer and the temperature is pretty steady. I think I will move the fuel bottles to my pole barn - which gets very cold in the winter and very hot in the summer. I may also sandblast several small nails to remove any coating and then drop them in to the fuel along with a small piece of aluminum, and maybe even a small piece of fuel line to see if the fuel starts to react with any of these items that could be fuel system related (fuel tank, carb, fuel lines, etc.). I am not suggesting that you leave your fuel in anything for longer than 2 months at a time......I just thought I would do a little research to see if I could learn anything.

 

[KD57]

I did that w/ oils years ago to see how it settled after storage. The only conclusion I came up w/ was the AV gas evaporated away real quick, and I was told it is because of additives to prevent icing at high altitudes. It took a long time before the pump gas started to deterioate, if I remember correctly, something like 6-8 months. Of course gas was different back then too.

 

[Termite]

Very interesting experiment. Keep us informed.

 

[mtfallsmikey]

Very good Banj!....unable to give you any more 'rep tho...

 

[Rookie1]

Very cool test. Lots of time involved. Keep us posted.

 

[oneoldbanjo]

This test isn't taking much labor.....just lots of waiting. The fuel in the bottles is not acting the way I thought it would. It has been in the bottles almost 9 months and it looks and smells just like the new fuel I am using. If I had left fuel in my motorcycle tank for this long it would be funky by now. I had a motorcycle that I recently bought that had fuel in for a little more than a year....and the fuel tank was getting rusty and the fuel was terrible smelling.

I believe one of the things that has kept this fuel relatively stable is that the garage does not have many temperature or humidity swings....and therefore little expansion/contraction is occuring in the bottles. If they were in an environment where the fuel/vapor would expand and blow gasses out in the daytime when it was hot and then pull in damp air at night when things condensed - it could make a difference in how the fuel reacts.

 

[brages]

I wonder if a metal tank (like a street motorcycle) has more of an issue with condensation from hot/cold cycles...

 

[mtfallsmikey]

I would say yes...you should see what condensation does to a fuel oil tank!

 

[ehgauss]

As an aside, actually three asides, 1. I recently checked out a Coleman gasoline stove that I hadn't used in probably 15 years. It still had Coleman fuel in the tank. It still smelled good, was clear, and lit right up (after I lubricated the pump) and worked well. It had been stored in my cellar (i.e., at very constant temperature). The Coleman fuel didn't seem to have deteriorated at all; 2. Last summer I took down a two cycle brush cutter that had been hanging on my barn wall since some time in the late 80s, the last time I recall using it. I expected to see that black crud in the fuel tank, but all that was there was the remains of the #30 weight motor oil that I had mixed 16:1 when I was last using it. The gasoline (probably 89 octane with lead, and certainly no ethanol) had all evaporated away. I flushed the tank with clean 40:1 mix, refilled it, opened the fuel valve (I had obviously run it out of fuel the last time I used it), closed the choke, and gave a few pulls on the starter. It started up and ran well. Over the years that it had hung, it had been exposed to temperatures as low as -25F and as high as 95F numerous times; and 3. Also last year, I checked the gas that had been in my outboard motor tank for about two years (87 octane with ethanol mixed 50:1 with Evinrude outboard oil). It was very cloudy. I didn't take any chances with and put it aside for use for cleaning parts).

 

[KD57]

One thing about old sour gas, you can smell it instantly when you remove the fuel cap. Nothing else smells like it, lol.

 

[blsnelling]

Thi really doesn't surprise me too much. So often what you read is just what someone said and was passed on over and over until it became the gospel. It's the "group think" mentality at work. I've never had fuel related issues. My 039 used to set for months with the same fuel. My trimmer and edger still do. And I've never had one fuel related issue. How much of the fuel related info here is based on fact or just surmising? It's easy to just say, "Oh, it was bad gas that caused my saw to burn up", when in reality it was something else. I personally find it hard to believe that fuel goes bad in a month or two. I'd have to see scientific testing to buy that.

Now after all that, I've bought into this thing. Just last week I purged all my saws of gasoline and filled them with AvGas. So I'm guilty too. I'm suspectful that AvGas is causing poor idling characteristics, poorer throttle response, greater chance of carb icing, and less power over all. Why? It doesn't burn as hot. Again, these are just my surmisings. I've yet to prove any of them to myself. I will be testing the power differences here soon though.

 

[oneoldbanjo]

We have a one gallon can of Coleman fuel that belonged to my wife when we got married, and it is more than 14 years old and still smells fine and looks perfectly clear and works just fine in our little backpack stoves. (We don't use Coleman fuel very often). My father in law just gave me a Stihl weedeater that was put away about 5 years ago and not run out of fuel, and it didn't have any fuel in the tank but suffered from a crispy fuel line and a honey looking stale fuel mixture in the carb. A neighbor gave me a motorcycle that had been stored for 5 years......it needs the carbs taken apart and cleaned as 2 of the 4 cylinders won't run at all (I tried opening the float bowl drains and flushing them with fresh fuel before I tried to start it).
I believe that the fuel will keep far longer in a sealed metal container than it will in a vented fuel tank or plastic container that is not well sealed.

I do know that some fuel systems are very sensitive to alcohol. My uncle had a 1970 Mustang and when the "new" and "improved" fuels came out we started having problems with the accelerator pump diaphragm. Each spring when we tried to start the car the would drip heavily out of the carb. What would happen is that as the car sat over the winter the volatile parts of the fuel in the float bowl would evaporate and leave a high concentration of alcohol behind - and it would eat up the fuel pump diaphragm. He no longer has that car and they may be making diaphagms now that are more compatible with alcohol in fuels. I also know that my mother's push mower will not start in the spring with the fuel that is in the carb - but it will run on the fuel that is still in the tank. I think that just like the Mustang the fuel in the carb has become a high concentration of alcohol and you can't get the mower to start on the alcohol - if I dump a little fresh gas down the carb a few times it will start and die - but about the third time the engine has built up enough heat or used up the alcohol rich fuel in the carb and will run. If I take the float bowl off and dump the fuel out in the spring then it will run normally. (I have not been able to talk her into remembering to run the fuel out at the end of the season).

My vintage motorcycles have bare steel tanks inside and they are very sensitive to moisture and the alcohol can attract enough moisture to rust them very easily - so I have started to coat them inside with a liquid pour in liner to protect them.

I have never had any fuel related problems in my chainsaws, weedeaters or leaf blower....they get used often enough to never have a problem.

Brad: I am not convinced and have never seen any evidence that higher octane fuels or Avgas burn "cooler", and I am not even certain that they burn any slower. I know that higher octane fuels are less prone to "detonation" and can stand higher cylinder temperatures and pressures before they stop burning at a controlled rate and cause "knock. I also know that if you set an engine up to run on a high Octane fuel by raising compression ratios and advancing timing you can get even more power - but a high octane fuel alone will not necessarily improve the performance of an engine that is set up to run on a lower Octane fuel. Perhaps the Avgas doesn't run as smoothly in your saws as the compression ratios and timing just aren't using the higher octane effectively. The Stihl manual recommends 89 Octane and the extra Octane of 100LL may not be needed or even helpful.

 

[blsnelling]

Most modern Stihls have a flap disc that seals pressure in the fuel tank. If there's a vacuum in the tank, air can be drawn in, but nothing gets out. Therefore, I don't see how therecan be evaporations problems in a chainsaw. Perhaps this is why I've never had a problem with them.

I hope to do some testing within the next few days to compare cut times with the same saw and chain and chainging only the fuel from 100LL to 93 octane gasoline. I'll report my findings here.

 

[oneoldbanjo]

[QUOTEI hope to do some testing within the next few days to compare cut times with the same saw and chain and chainging only the fuel from 100LL to 93 octane gasoline. I'll report my findings here.[/QUOTE]

Brad: That will be interesting to actually see the results. For my basically stock saws, and for my standard firewood cutting techniques I really don't see any difference between the use of 89, 92 or 110 Avgas in the way my saw runs or cuts (Once the mixture has been adjusted for the switch between pump gas and Avgas). I do not time anything.....just cutting away at firewood with a normal saw and reasonably well maintained chain. The only reason I tried using Avgas was to help avoid problems with alcohol in pump gas. I have noticed that my rectangular plastic fuel jugs get a whole bunch rounder in the summer than the ones that I have pump gas in.....I guess the vapor pressure for Avgas is higher and the fuel jugs build up more pressure.

 

[K9-Handler]

More fuel

I agree with Brad.

I keep a few 5-gal plastic tanks of fuel around to power a generator "just in case". They get rotated through mowers and other implements, but not at a huge rate, so especially in the winter they just sit and sit in a semi-heated garage. They might get Sta-bil if I remember to put it in, but most of the time I think the tank will be used up before long term storage so I just don't.

I have a nephew from the upper midwest who owns something like 5 ethanol refineries (yeah, the rich side of the family). When he came out east last summer we sat and had a discussion about ethanol fuel. I had just had a bad experience with a stored saw that absolutely would not start -- not even a sputter -- and my dealer got it running after a carb rebuild. The dealer said that a large percentage of his service business is now ethanol-related. Most homeowners use the lowest octane gas they can find and it craps up the carbs and the fuel doesn't last (dealer talking). So I put that to my nephew and he disagreed. Not surprising -- he doesn't want to be the bad guy. But I said that everybody here hates ethanol and you can't deny it's a problem. But he explained it this way. The ethanol is different than gas, and acts almost like a detergent. Some of you remember when motor oil was detergent or non-detergent -- they would warn you not to put detergent motor oil in an old engine because there would be a sudden rush of sludge that had settled out of the old oil into cracks and crevices that would now be held in suspension in the detergent oil. Same kind of thing with the ethanol. Machines that had been running regular fuel would leave harmless deposits. The ethanol would dislodge the deposits and cause problems. However, once cleaned out, there would be no more deposits and the ethanol would work OK. I was skeptical, but in my experience he's yet to be proven wrong. Once I've run something for the first time on ethanol gas and gotten the problems worked out, the thing runs fine.
My nephew did say that you needed to keep caps on tight. Obviously alcohol evaporates quickly and also might attract water. The smallest vent hole (to allow for expansion/contraction) the better.
I keep expecting to find bad gas in my 5-gallon generator tanks, but so far it hasn't happened.

Now small fuel tanks on things like lawn mowers or snowblowers are an exception. If I left some in when the thing got put away I always drain and rinse before attempting to start for the first time in a long time. Those always smell bad, anyway. :fart: Dead giveaway.

 

[teacherman]

I can notice a difference in smell after a few months, and I use only Amoco Gold 45:1 with Stihl Ultra in a new plastic can.

 

[Lakeside53]

Brad: I am not convinced and have never seen any evidence that higher octane fuels or Avgas burn "cooler", and I am not even certain that they burn any slower. I know that higher octane fuels are less prone to "detonation" and can stand higher cylinder temperatures and pressures before they stop burning at a controlled rate and cause "knock. I also know that if you set an engine up to run on a high Octane fuel by raising compression ratios and advancing timing you can get even more power - but a high octane fuel alone will not necessarily improve the performance of an engine that is set up to run on a lower Octane fuel. Perhaps the Avgas doesn't run as smoothly in your saws as the compression ratios and timing just aren't using the higher octane effectively. The Stihl manual recommends 89 Octane and the extra Octane of 100LL may not be needed or even helpful.

yes.. AV doesn't doen't "burn cooler".. and.... even if it did, that has nothing to do with carb icing.


The A L K Y L A T I O N process used to make Coleman fuel (and ASPEN) is similar to that of Avgas.. which is why it stays good for a very long time. Colemen is however only about 55-60 octance, so keep it out of your saws..

AVgas does have additives...

And.. for those that want to know more :

http://www.fpp.uni-lj.si/~mtone/Izbrana poglavja zracnega prometa/Letalski_motorji/knj11.pdf

If you want to accelerate the test, put the bottles outside in sunlight..

 

[oneoldbanjo]

Andy:

That is a good point about sunlight. The garage where the bottles are being kept only has one window in a 22x40 space, and it faces in a direction that never gets any direct sunlight. My pole barn doesn't have any windows and only gets daylight if I open a door.

I don't want to accelerate the test beyond the conditions that my stored fuel would experience. I think that where I could get in trouble is that with so many pieces of equipment to keep running......it would be very easy to accidently let fuel stay in a piece of equipment waaaay too long. And even as I type this I can remember that we have a gasoline powered blower sitting downstairs that we use when testing sanitary sewers.....and I know it hasn't been run in two years. I doubt seriously if anyone has bothered to run it out of fuel!

 

[blsnelling]

And even as I type this I can remember that we have a gasoline powered blower sitting downstairs that we use when testing sanitary sewers.....and I know it hasn't been run in two years. I doubt seriously if anyone has bothered to run it out of fuel!

There's a test for you right there! Pour it in a glass jar and take a look at it.

 

[oneoldbanjo]

There's a test for you right there! Pour it in a glass jar and take a look at it.

If it doesn't pour anymore......maybe I can use a spoon!