Best gasoline to use in a M38A1

[FireFighterHill]

Alot of guys in the landscaping industry swear by this stuff
Star brite Star Tron Gasoline Additive

 

[steelypip]

The way I understand the use the ethanol is really just a filler or extender. Has very little to no fuel value in most engines. Anyone know of this for fact or bs?

You've stepped into one of my areas of competency. I worked in a vehicle emissions lab for about five years analyzing gasoline before and after it went through an engine.

Ethanol makes a pretty decent fuel for an Otto-cycle engine. Not as good a fuel as toluene or 2,2,4-Trymethylpentane (Iso-octane - 100 on the octane scale), but a pretty decent fuel. Its knock resistance is pretty good (109). Its major downside from a combustion point of view is that there's already some oxygen in the molecule, so it's not as energy dense as petroleum distillates are.

Unfortunately, it's also a lot livelier chemically than the hydrocarbon soup we call gasoline. Ethanol happens when yeast eats sugar, and it, in turn, is eaten by a lot of other life forms, including humans. Anything that can be broken down chemically for energy is food for something. The problem is that ethanol is pretty easy to digest, so it's food for a lot more things than petroleum is.

There's another problem with ethanol - it is hygroscopic (absorbs water out of the air). Fuel tanks and temperature changes make a natural water trap. Put a half-tank of ethanol in a vented fuel tank and you will have a saturated water-ethanol solution very quickly. And a saturated water-ethanol solution is what microbiologists call 'growth media.' It's perfect food for all manner of alcohol-eating microbes and their friends and hangers-on.

Ethanol also is a solvent to different things than gasoline is. Not a better solvent, really, just different. (I'll avoid going into solutions chemistry explanations of how it is different). That difference means that elastomers (rubbers and flexible sealants) exposed to ethanol may or may not survive the experience.

Fuel blenders have been using ethanol ever since MTBE was banned back in the '90s (I always liked MTBE-spiked high-test myself, but Alaska didn't). It's not a bad way to bump the octane number of a fuel, but you will decrease the energy density with it. But, along with the removal of tetraethyl lead, it has made gasoline much more interesting to microorganisms. That's what gets you that awful brown gunge in the fuel pump and float bowl when you park something for a while.

Of course, nobody would bother doing it if it weren't heavily subsidized by the government as a sop to ADM and the corn farmers of the midwest. If you don't like ethanol in your gas, take it up with your congressman.

The sad part is that a mil-spec gasser like a Jeep, half track, or CCKW can burn nearly anything called gasoline that comes out of a refinery. What you guys really want is the low octane feedstock before they put the ethanol in it - Coleman fuel would probably work. It would have high energy density, be pretty cheap, and would still be 82 or so octane. The last thing you need is a fancy, leaded low-volatility, expensive avgas. There's nothing wrong with avgas, but it's kind of like putting titanium shoes on a plow horse.

 

[jamesfrom180]

Awsome, I deal with gasoline in groundwater and will say MTBE does not need to be handled by the public. Not that the effects are really toxic just it moves too freely through our world.

I might just be stripping ethanol from my fuel before storage now. This has been a pretty useful topic so far.

 

[FireFighterHill]

Are you sure coleman fuel is that high of a octane rating? I just googled it and the consensus is that its octane is 50-55.

 

[ProviderDriver]

Cool explanation! I am buying 100LL Avgas for around 5.50 a gallon average... It's still a whole lot cheaper than most fuels... I am curious how expensive Coleman fuel is, I always thought that stuff was white Kerosene, not gasoline...

Yikes! I just looked up Coleman fuel... I don't think I would be running that in my engines anytime soon... just my 2 centavos

 

[emr]

the truth is gas is pretty simple, the higher the octane the cleaner the fuel the higher up the cracking tower the cleaner and more expensive the fuel, no matter how hard some may want to make it it is that simple, as for your motor super is always better simply because of less deposits ijn the motor, and easier starting, and will last longer than lower octane fuels when sitting, oh yes it does, as for any gas is ok is very true too, your m 38 will survive just fine on all of them, it has proof of time lead will not be a problem for U, i will throw in i put about 65000 miles on my m 38 in 25 plus years running only super, after long sits it was/is always fine, my X brother in law is an engineer in a refinery in texas and filled me in on the basics years ago, opinions run rampent in this and about oil, oil is simple too, the most important things on oil is, all mix and any oil is better than no oil, lighter is for tighter motors and colder climates heavier is for bigger looser/older motors and hard running along with hot climates.... use this info as u want, it is all true... without all opinions about what is out there this is the answer to your question... good luck... randy........... oh i have just seen alot about newer fuels ruining types of lines, not a prob, they said all that about the new diesels and absolutely none of that has ever happened either, its opinions, if U want and like those answers thats up to U, its your truck, your truck ran on crap in service , its an upgrade no matter how u look at it today.

 

[saddamsnightmare]

June 10th, 2011.

Gents:

Say what you will about Ethanol.... It IS BAD S**T! I have spent about $1500.00 to correct ethanaol related problems with my 1963 MB S404.114 Unimog, and the local MB genius has taken if from a truck that could run 6 miles without gas related stoppages, to one that can't get out of a 100 foot driveway without stoppages. In Texas this truck ran better then 4500 miles a year, often on two or three hundred mile trips, since it has been up here in Illinois, where Ethanol is about all they have, it has destroyed three MB fuel pumps, one MB tank selector valve, several hoses and is destroying the original tank protective linings..... I have never seen a truck engine react this way, but then, the Texans don't grow corn, so they don't want or need ethanol. I have replaced the mechanical pumps with an electric pump and pressure regulator, pre and post pump filters, and still the truck won't run, and IT IS all fuel system related issues that MB Unimogs are never known to have.... unless they are exposed to Ethanol.
There are NO conversion sets for the rubber components, as the other S404.114's in the rest of the world are not exposed to ethanol, I can't wait until they up it from 10 to 15%, that should kill the truck dead. IF I had the money, I'd convert her to diesel, as the truck only has 24,000 miles on it from day one. I would be afraid to expose a deuce to this stuff, as it would surely destroy it's fuuel system also.... political hocus pocus is what it is and will be....

 

[wdbtchr]

I might as well add my worth to this discussion. I've been using water to remove the ethanol from regular gas for my tractors and small equipment since they started adding it. I bought AV gas for a while, untill it got crazy expensive and harder to get at airports due to increased security. I finally decided even loosing 10 % removing the alcohol it's still way cheaper than buying AV gas. I haven't had carb problems for years. I do still use AV gas in my '68 Camaro though, at almost 12 to 1 it really needs it.

 

[stumps]

y........... oh i have just seen alot about newer fuels ruining types of lines, not a prob, they said all that about the new diesels and absolutely none of that has ever happened either, its opinions, if U want and like those answers thats up to U, its your truck, your truck ran on crap in service , its an upgrade no matter how u look at it today.

Ah Randy, it's great that your life is so simple. I spent the early part of this winter replacing all of the rubber fuel hoses, fuel pump diaphragm, and gaskets on my Bobcat. This spring, it was the float valve on my tiller, and the fuel hose.... again. I am having good luck with my tractor, as it is gravity feed, all steel line, and a stainless steel float valve... no rubber anywhere. But that is it. I also had to rebuild the carburetor on my chain saw, and weed wacker, and replace the rubber with the alcohol kit.

But as you said, the rubber damage by the new gasoline is all opinion... NOT!

I wash my gasoline now.

-Chuck

 

[emr]

Thanks! I am glad too Well it never happened to me or anyone i know, I guess i have to ask why does it not happen to everybody?, just wondering, and it is simple, as for anything they add to extend gas, I think its stupid, I also think ethanol is stupid, but over all what i said is true, it will not hurt his Jeep. and the basics still hold true in what i said.

 

[stumps]

Thanks! I am glad too Well it never happened to me or anyone i know, I guess i have to ask why does it not happen to everybody?, just wondering, and it is simple, as for anything they add to extend gas, I think its stupid, I also think ethanol is stupid, but over all what i said is true, it will not hurt his Jeep. and the basics still hold true in what i said.

Hi Randy,

The M38 Jeep is almost identical in terms of the fuel system to my '70 Bobcat. There will be problems with the fuel pump, and if a newer carburetor kit has been installed... one that has a rubber tip on the float valve, there will be problems with it sticking too. Rubber hoses become brittle from the alcohol, and will crack. It is just a matter of time.

The sad problem is all of the material problems could and have been fixed in the later vehicles... those made after about the early '90s. But, the stupid manufacturers haven't done anything to use better rubber like materials in the kits that are being sold to rebuild the older carburetors, fuel pumps, etc. The brand new, built last year, fuel pump that I bought to fix the problem with my Bobcat, worked for exactly 2 days! The rubber gasket that sealed the dome to the top of the pump swelled up from exposure to the gasoline, and when I removed it, it was about half again as big in circumference as it needed to be. I had to make one out of cork to get the beast going again.

Fortunately, the kits for the little 2 stroke buzz box engines that use Walbro carburetors generally have a white, alcohol safe, flapper valve "gasket" that doesn't care about the alcohol.... but they also include the black rubber style where the flaps curl and cease to pump the fuel.

If you haven't been having problems, you are blessed. Possibly your area hasn't gone whole hog with the E10 deployment. Mine hadn't until last Summer.... Before that I could still get alcohol free gas from some of the stations. Now my tests show that they are all selling E10.

-Chuck

 

[steelypip]

The M38 Jeep is almost identical in terms of the fuel system to my '70 Bobcat. There will be problems with the fuel pump, and if a newer carburetor kit has been installed... one that has a rubber tip on the float valve, there will be problems with it sticking too. Rubber hoses become brittle from the alcohol, and will crack. It is just a matter of time.
-Chuck

Just to fill in a little here - most people who seriously drive Corvairs have gone to electric fuel pumps. Nobody seemed to be able to make an E10-compatible diaphragm material for that pump for whatever stupid reason. I didn't mean to minimize the effect of ethanol on elastomers - I just thought it was a well-known problem, so didn't spend much time on it. The question asked was about the quality of ethanol as a fuel - it's a pretty decent fuel, it's just not chemically compatible with a lot of the rubbers used in older gasoline fuel systems.

Are you sure coleman fuel is that high of a octane rating? I just googled it and the consensus is that its octane is 50-55.

Yep, you're right. I was thinking of distillate spiked with reformate, which is a primitive blend, but can have pretty good octane numbers. Reformate is made from naphtha (white gas/Coleman fuel) but ISN'T naphtha.

Awsome, I deal with gasoline in groundwater and will say MTBE does not need to be handled by the public. Not that the effects are really toxic just it moves too freely through our world.

I might just be stripping ethanol from my fuel before storage now. This has been a pretty useful topic so far.

So what's your take on ethylene glycol? It's just as environmentally mobile and just as unfamiliar to soil bacteria...

 

[jamesfrom180]

Simple ethylene glycol is not normally stored in the ground. Exposure is within the aerated and aerobic zones of most soil. This allows for mechanical stripping. Bacteria are a wonderful tool for us who clean up this stuff. Degradation of MTBE by microbes is debated. I also believe that at least the parent structure of glycol only has an acute effect and has little chronic toxicity. Daughter products would be my biggest worry. Over 50 gallons of milk can be considered a public health risk and environmental pollutant when spilled. My general rule of thumb is simple if animals have been exposed to it for over a thousand years you can predict what the chemical will do. Anything less than that you are playing Russian rue-let.

I do know of some systems that have used ethylene glycol pumped into wells for thermal dissipation. Heat pump systems. Like any engineering system you can really screw things up when designed or operated improperly. So those are my thoughts on ethylene glycol. I imagine when I have the chance at working on a glycol spill I may have new or different views. We live in a scary world where alot of different things can kill you. I personally like sustainable fuels. I think these should be a goal for us and our future. I will just remain guarded about any new technology.