Generator Fuels, BTUs/KwH

Those who visit Utterpower often, likely found Neil’s rant on the Free Generator page. Sure, we’ll all question why  he couldn’t make the comments against a post on the same topic, but fact is.. there’s plenty of people who think ethanol is great stuff. I’ve even found people who said they’d gladly pay double the price of gasoline for straight ethanol if they could get it, and it would burn in their flex fuel car, generator, weed eater, etc.

For many of us, we know there’s no magic when it comes to fuel, ethanol has about half the BTUs per volume as gasoline, and we know that diesel has a lot more than gasoline.

We might be forced to run this stuff in our older equipment, and we should expect to get less mileage or less KWhs of electrical energy production for a given volume of fuel. If we add 10% ethanol, we should expect 5% less work to be done.

If you are running an old Flathead engine, it might be a good idea to get one of those inexpensive non contact thermometers and look at the temperatures right at the exhaust, in our carbureted engines, there’s no compensation made for the leaner fuel mixture than ethanol blends deliver, and you may need to adjust the main jet to deliver a little more fuel to assure that you don’t exceed the temperatures your engine was designed to run at.

Engines made today are adjusted at the factory to run on ethanol blends and when things are right, they will run more fuel through the engine to keep it cool.

Of great interest to me are the claims that some fuel additives cure all the problems that ethanol blends create. I’d like to hear from a Chemist what type of additive can prevent the ethanol from combing with water and eventually dropping out of solution?

For those forced to run Ethanol blends, it does sound like we should apply these precautions.

  1. Make use of plastic fuel tanks with vents we can close when not in use to assure moisture laden air is not drawn into the tank during the daily temperature cycle and condensed into the fuel.
  2. Use a positive shut of valve or similar and run the unit out of fuel after each use. Do this during ‘no load’ conditions.

I welcome any discussion as to the technical merits of fuel additives to control this ethanol/water attraction.

Have you ever wondered how much coal we burn to make the energy to make a gallon of ethanol?


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15 Responses to Generator Fuels, BTUs/KwH

  1. Quinn says:

    George, another way to minimize the problem with oxygen and moisture contaminating the fuel is to minimize the volume of air in the headspace above the fuel by keeping the tank or fuel container full. Many plastic tanks, like those for outboard motor fuel, have a vent that can be closed. Certainly minimizing temperature swings also minimizes the puffing of the tank. Your climate is about as bad as it gets for storing gasoline.

    Water contamination used to be a big problem with gasoline because water and gas are nearly immiscible. But ethanol and water are infinitely miscible. And at 10% ETOH in gasoline, the blend can absorb and hold appx. 0.5% by volume, or 19 ml (a little over a tablespoon) of water at 60 deg. F. before the water separates and forms a puddle between the gasoline and the bottom of the tank. So ethanol addition to gasoline actually helped solve one common problem. However, the problems it created by holding water in close association with the volatile components in gasoline have created chemical compatibility and stability issues that have caused problems for manufacturers and owners of pre-gasohol ready vehicles.

    For what it’s worth, I think the real problem with gasolines today is that they are not the simple blends of straight chain organics that they were when we were kids. Now gasoline is a complex blend of many components that have been introduced for the sake of economy, performance and to suit the dictates of the EPA. Like the KISS principle, the more complicated your design, the more things that can go wrong with it. The complication of what was once a simple blend is, IMHO, what has caused the shelf life of gasoline to plummet in recent years.

    • Homealone777 says:

      Well; It’s been a little while since I posted on here, and in that time I’ve learned a lot. From what I know now; The gasoline we’re burning now may be 10% ethanol, but it’s only about 10-20% true gasoline. The other stuff called ”Feedstock”, is mostly chemicals. Butane has a low boiling point, and evaporates easily; And then there’s Naptha, which has it’s own unpleasent properties. Anyway, to shorten this; I’ve learned through my searching that there are about seven major chemicals, along with quiet a few others. Check it out for yourself by searching gasoline additives. Back in the late 70’s and early 80’s, I had a gallon bucket of gasoline with a lid on it for washing parts off and we never had any problems with getting it on our hands except for going back in the house to wash up; We had to pass by that warm morning stove! In the winter, that was a little nervey even though you’d dry you’re hands as best as possible! About five years ago, when came back off the road; I started working back in my garage, with my old ways of washing parts. But something was wrong; when got this new gas on my hands they would turn white and tingle for a while even after I cleaned up. Now I know why. I went and got me a parts cleaner, and Lord Willing; I’ve had no trouble since. I don’t use gas for parts cleaner anymore. Anyone who does it might ought to check it out first. I don’t know what the long term effects are, but I’m not going to go back to it. You know, gasoline being that well mixed makes me wonder,”What gas shortage!”

  2. George B. says:

    great addition Quinn,
    I’d like you to expand on one bit of your post.. as I saw it, gasoline and water were far less of a problem, as they did NOT mix.. a water trap allowed us to remove or separate the two. re read your post, did I miss something?

    One of the problems with Ethanol is it will drop out, and burning a slug of it can cause a super lean condition that can cause damage. Furthermore, once it does drop out, the octane rating of the gasoline itself can be too low for the engine and pre det can further damage the engine since the formulation relied on the ethanol as an octane booster.

    you mention of keeping tanks full when possible, always a good idea, but not humans forget. A bladder within the tank might help with this situation.

    • Quinn says:

      First point, I think we both agree that water doesn’t belong in your gas tank. But when it gets there, we have only two good ways to get rid of it. The first way is to collect it in a trap in the bottom of the tank and remove it through the drain plug. Most cars have, or used to have, drain plugs in the bottom of their tanks. But the risk of leaks is too great in some installations. For instance, in marine installations, USCG regulations mandate that all penetrations through the walls of a fuel tank must be made only through the top. A portable outboard motor fuel tank is an example of what the USCG likes to see. On a boat with a permanent fuel tank, you’d better have a good water separator installed in-line. So water in your gas tank can sometimes be difficult to get rid of for the very reason that it does not mix with gasoline.

      The second way to remove accumulated water is to dissolve it. Commercially available water removers are usually methanol, an alcohol very similar to ethanol. Alcohols have the ability to dissolve water and to be themselves dissolved in gasoline. With the addition of ethanol in gasolines, any water that accumulates in the tank, up to 0.5% by volume, is absorbed by the alcohol and remains associated with the alcohol, which mixes infinitely with gasoline. The water dissolved in the ethanol, which is in turn, dissolved in gasoline burns with no noticeable effect, other than perhaps to reduce combustion temperatures a bit, which can sometimes be a good thing.

      So if you don’t have a water trap or a drain plug in the bottom of your storage tank through which to remove any accumulated water, the ethanol content in modern gasoline might be seen as a benefit because it prevents water from accumulating in your tank.

      Re: your second point, ethanol won’t separate from gasoline all by itself. What you may be describing, however, is that if water accumulates past the 0.5% volume limit, then any additional water has nowhere to go and it WILL accumulate in the bottom of the tank. And since water and ethanol are mutually miscable, that puddle of water will contain some ethanol from the gasoline. But by the time that happens, your gasoline/ethanol blend is already saturated with water and it simply can’t hold any more. At that point, you’re no worse off than you would be if you were using straight gasoline.

      So if you’re faced with the problem of water in your fuel tank, your choices are to drain or suck out the accumulated water from the bottom of the tank, or add methanol or ethanol to dissolve the water. And if you do the latter, like folks have been doing for years, you’re burning essentially the same blend that we’re all forced to buy at your local gas station.

      I probably used too many words to describe that. I hope that was clear enough.

      I like the idear of the bladder. My Prius (yeah, I know, but it’s ridiculously cheap to drive) has one for evaporative emissions reasons, but that’s an excellent way to minimize the headspace within a gas tank. Sort of like an IV bag. As it empties, the bag just deflates.

  3. George B. says:

    Quinn, we need pin some of this down.. my info is that ethanol won’t blend with gasoline unless it’s absolutely dry… zero water…

    Second.. some sites that are dedicated t this subject say the alchhol will divorce itself from the gasoline one it takes on enough water.. so if you’re right… then they are wrong.

    • Quinn says:

      That’s correct, so far as initial blending goes. The ethanol that is used in making E10, or gasohol, or the pump gas that we are forced to use, is made with anhydrous ethanol, not the stuff Grandpa cooked up in the backwoods still. The traditional method for making alcohol from fermentation involved a distillation step to separate the alcohol from the water. But distillation is only effective up to about 95% purity. 5% water remains because at that level, the alcohol and water have such an affinity for each other, they form a constant boiling mixture called a binary azeotrope. You can boil and boil the stuff all day and you’ll never get 100% alcohol, called absolute, or anhydrous ethanol.

      In order to separate the alcohol from water entirely, which is necessary before it can be blended with gasoline, ethanol producers have more recently employed molecular sieves In this process, ethanol vapor under pressure passes through a bed of porous beads. The pores are sized to allow absorption of water while excluding ethanol. After a certain volume of crude ethanol has passed through the bed, it is regenerated under vacuum or by passing dry nitrogen through it to remove the absorbed water. Then the bed can be used again. In that way, the energy intensive process of distillation can be avoided, saving energy during processing.

      Now, once the ethanol has been rendered anhydrous, it can be mixed with gasoline. Once that blend has been made, the ethanol can absorb water up to appx 0.5% by volume, after which the water will begin to separate. And since the water and ethanol are mutually soluble, the water puddling in the bottom of the fuel tank will take some of the ethanol with it. That’s probably why some folks say the ethanol is dropping out. The exact amount is going to depend on temperature. I don’t recall off the top of my head which way the solubility of water in ethanol/gasoline goes. I suspect as temperature drops, the solubility of water in ethanol also drops, but it’s been a while.

      So you’re correct. Anhydrous ethanol is required to in order to blend with gasoline. However, once it is blended, it can absorb a small quantity of water and remain in solution. Beyond that 0.5% level, the water and alcohol begins to drop out.

      • George B. says:

        OK, I guess we’re on the same page.. but of course.. you’re the chemist, and I’m the DIYer that’s read some on ethanol blended fuels.. “a big difference for sure”. I think we agree, there are lots of things we can do to make this fuel less of a problem in older generators, but in an area like mine, you can have some serious problems in a fairly short time IF you don’t address them. Of course getting the fuel mixture right in the first place is step one, and we know this stuff forces our engine to burn leaner and hotter..

        We still didn’t get around to discussing an addative that might make this stuff keep a lot longer.. the outboard motor shops say you’ve got to us it.. I can’t imagine how it helps with moisture….

        • Quinn says:

          I didn’t address it because I don’t know how it works. I’ve always just used Sta-Bil in my small engines and it’s worked fine. Petroleum chemistry is a pretty complicated field these days. I know only what I learned of it in college and what reading I’ve done on the side, so my knowledge is really pretty basic organic chemistry. If anyone reading anything I’ve written wants to scream B.S. I’ll happily stand corrected. I DID, though, have the opportunity to spend about a week installing, tweaking, and training my cohorts on a new gas chromatograph and just for grins, I injected some gasoline on the column. The computer monitor just about turned green from all the peaks that began showing up. While I couldn’t identify any on the components because I didn’t have the software loaded, that showed me that there’s lots of stuff in modern gasoline.

          The Sta-Bil website has lots of interesting looking links. Haven’t read them, but you might be interested.

          • George B. says:

            “new gas chromatograph”

            Wow! what a fun toy…. so… when are you going to get the software, and can we dump someWD40 in there??

  4. George

    I have previously used Fitch catalyst to keep unleaded E10 fuel fresh in small engines and not had any corrosion problems even after 6 months in the tank – monitoring it monthly – I still like to keep fuel fresh – our carburettors are still adjustable – so I guess we dont really want progress – some engines are starting to have micro fuel injection systems so they can be impossible to repair once parts are no longer kept. They make more money from it by having oxygen and air flow meters – cheap to make but big $$$$s to keep the engine alive down the track.

    I know a lot of military applications and gasoline engines here use E10 fuels have Fitch catalyst pellets – a lot of mining companys also use it is their diesels to reduce exhaust emissions underground – it comes from the USA – so you should be able ot obtain comments from people over there involved with its production USMC etc. I am not sure but I was told it is a tin based product.


  5. Homealone777 says:

    Back around the time frame of the 50’s- 60’s; They had a small glass bowl you could take off and dump the water and impurities out before they got to the carb, providing it was’nt too much. But anyway, you could see the gas before it went into the carb. I started noticing them making a comeback at the car show’s I go to. At first I thought it was cosmetic, but they were putting them on there because of the ethanol. And they were putting them close to the carb so they could see what was happening. I thought it was a smart move.

  6. Homealone777 says:

    Oh yeah; That old Onan genset I’ve been working on is a model 6.5 nh 3cr. I’m hoping to get it going for this winter as a backup power system, and make use of that remote start system for my little woman. Lord Willing, if everything works out right; It should be a nice setup.

  7. Homealone777 says:

    BTW, I got to tear into one of those CARB carberators; Boy what a mess! A friend of mine wanted me to check it out and get it running for him. I don’t know how long it had been since ran, but it had been at least 2 years. Lord willing, I had another one like it, and it needs soaking. The old carb looked like someone had put wood varnish in it, and maybe a little acid! I doubt soaking it would do much good. For the last 3 or 4 years, every time I tear into one, there’s always been what looked like acid based water at the bottom of them. It makes the alloy canker, like it’s been sitting for years when they’d been run the previeous year, or almost new. At first I did’nt know what was causing it, but after I started learning a bit about these computers; You’re site was the one that explained it to me. So that credit goes to you, George B. I thank you. Now I understand why so many of the small engine shops are going under,or learning something knew.

    • George B. says:

      You can still buy carb cleaner in a spray can (outside California) if anything will clean the carb this will.. older carbs were designed to be cleaned, you can get to the jets and even run a numbered drill through jets if need be. one small engine mechanic I know with 50 years of experience said the only thing that would clean the inside of the main jet in one carb he was attempting to clean was a numbered drill, he had tried soaking the carb and blowing out the jet first. But remember, these were the older carbs, the newer ones were designed in such a way that it is impractical to clean one.. you are forced to replace it at far greater expense.

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