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Discussion Starter #1 (Edited)
For my new 590...have not used it yet. I've always stored my gas in metal cans - a 5 gallon and 2.5 gallon. I keep it for months at a time and never used stabilizer when running my Cub Cadet for over 36 years. So I suppose - if the owner's manual is presenting sound advice relative to this - that the newer EFI engines are more critical as to the type and condition of fuel used? Any advice before I pour in stuff that's been in my metal can for at least the past few months? I'll check today to see what the octane level is where I usually buy gas for the tractor. Thanks...
 

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Hiya,

If it's ethanol blend with no storage additives in it, dump it in your car and go get fresh fuel and add a ethanol stabilizer to it or better yet, find ethanol free fuel. Local airfields will normally sell "auto gas" aviation fuel out of the pump, that is ethanol free and has no pollution additives in it as they don't want fuel issues at 5000 feet... That's what I use in my 4 stroke small engines.

Tom
 

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There is nothing special about the way fuel needs to be stored for EFI engines compared to carb engines. Chances are whatever fuel containers you are using now will be just fine. If they are old I would check to ensure they are nice and clean inside with no rust. If they are a little on the funky inside then it might be a good opportunity to get a new can.

I do recall reading something about issues with storing diesel in galvanized containers.

The most important thing is that the container be clean inside (and outside too as outside dirt has a tendency to work its way inside). Even though your tractor has a fuel filter it's always best to ensure whatever you pour in the tank is as clean as possible.

It's always best to use Ethanol-free gasoline if you can. Although without a carb bowl for fuel to sit in EFI engines seem to deal with Ethanol a bit better. Whatever you use I would recommend a good fuel stabilizer like Sta-Bil (although there are other good products on the market as well).
 

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Your owner's manual says "Store fuel in plastic containers to reduce condensation." and that's a general "makes sense" sort of statement. If your fuel storage can is left in an unheated/cooled shed where it is subject to temperature swings, you'll get condensation. If it's stored in a temperature controlled garage your risk of condensation plummets. So you have to look at how YOU store your fuel.

Ethanol in most commonly available gas sucks up water. That's just the way it works. So you're options are to avoid ethanol when possible, use additives to control water absorption or find ways to prevent water from getting into the fuel entirely (or any combination of the above!).

None of this is unique to an EFI engine. It's due to the changes in the gas, not the engine.
 

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And as far as condensation goes, the absolute best way to combat that in both gas cans and the tank on the machine is to keep them full when not in use. A topped off tank and topped off gas can has no surface for condensation to form. So when you're done with the machine for the day, top the tank off as the last thing you do.
 

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Generally speaking, ethanol in gasoline is evil. It is hygroscopic, meaning it attracts water. Its use was mandated as both a way to replace MBTE (an oxygenate) for reducing ozone emissions and a pact with agriculture to increase the market for corn. In some regions it is not required or is only required in the summer, but fuel blenders usually sell into widely divergent geographic areas and often have to blend to the worst case conditions.

Where I live, a lot of premium gasoline is ethanol free year round. Since my BMW specifies a minimum of 91 octane, I fill up all the gas containers with it when I'm topping up the car and use it for the small engines, boat and snowmobiles.

I suspect the caution against using anything but plastic containers is the possibility of rust forming in the can and finding its way into your fuel system.

Buy the ethanol free premium gas, store it in any approved container and don't worry.

Al
 

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Your owner's manual says "Store fuel in plastic containers to reduce condensation." ...
Condensation forms whenever the temperature of a surface is less than the dew point of the air in contact with it. It doesn't matter whether the surface is metal, plastic, grass or whatever. Plastic will not reduce condensation but, unlike steel, will not rust in contact with water.

Al
 

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I agree with most everyone else.
Condensation doesnt care what material it collects on. Cooler surface plus warmer air means condensation.
The way to stop it in fuel containers is to keep them sealed. If you cant keep them completely sealed (I dont), keep them full (I dont).

Ill say too that Ive found that leaving cans on the concrete floor of the garage means they are generally colder than the air temp, because if the concrete isnt insulated from ground contact, it will generally always be colder, and keep whatever is sitting directly on it colder too. This is especially bad regarding condensation in the Spring and Fall, where temps can vary wildly, at least around here.
I also run only ethanol free fuel in all my small engines. Each 5 gallon fuel can is also treated with 1oz of Mercury Quickleen and 1oz of TCW3 ashless 2 cycle oil. Since doing that, I have NEVER had a problem with fuel, no matter its age or storage. The Quickleen cleans everything and keeps it that way, and the oil, should the fuel evaporate, leaves a nice protective oil coating on everything preventing any kind of oxidation (learned that little trick from a Kawasaki Concours (among others) carb guru). The oil also acts as an upper cylinder lube, which isnt necessary, but it does help if you like that sort of thing.
Incidentally, I used to be a fan of Seafoam until I spoke to a few marine mechanics who said that it works ok, ,but Quickleen is much better.
Its also cheaper overall to use.

Also, you can run whatever octane you want. Your engine doesnt need anything more than 87, and wont work any better on anything higher. The only reason I see to run higher octane is that most non-ethanol fuels are higher than 87 octane.
 

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Also, you can run whatever octane you want. Your engine doesnt need anything more than 87, and wont work any better on anything higher. The only reason I see to run higher octane is that most non-ethanol fuels are higher than 87 octane.
I don't fully understand the chemistry, but ethanol is an octane booster. As octane goes up, the fuel can (not will) burn slower and more completely, allowing the ignition timing to be advanced and more power produced without knocking. When you get to 91/93 octane gas, you can't add enough ethanol to reach the octane spec without going beyond the E10 standard most modern engines rely on. I suspect blenders either add iso-octane to get the last few octane numbers out of the blend or skip the ethanol altogether and just use iso-octane. The latter is your ethanol free gasoline.

Al
 

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I don't fully understand the chemistry, but ethanol is an octane booster. As octane goes up, the fuel can (not will) burn slower and more completely, allowing the ignition timing to be advanced and more power produced without knocking. When you get to 91/93 octane gas, you can't add enough ethanol to reach the octane spec without going beyond the E10 standard most modern engines rely on. I suspect blenders either add iso-octane to get the last few octane numbers out of the blend or skip the ethanol altogether and just use iso-octane. The latter is your ethanol free gasoline.

Al
Not entirely right.

The Octane Rating of a fuel is an expression of the fuels resistance to "pinging" or "knocking". In a Gasoline engine pinging and knocking occur when the gasoline starts to ignite during the compression stroke due to the amount of heat in the cylinder. This type of ignition occurs prior to the spark plug sparking.

So in other terms the octane rating of the fuel tells you how resistant the gasoline is to turning your gasoline engine into a diesel engine. This is why using high octane fuel is important in high compression and or turbo charged gasoline engines. Having the fuel ignite prior to the spark plug telling it to can do some really horrible things to an engine.

Ethanol as an additive to gas is a very effective octane booster. It is also relatively cheap and more environmentally friendly than other octane boosting additives. Not surprisingly this is a major reason there was a regulatory push to use it. Despite its drawbacks ethanol makes the air coming out your tale pipe less harmful. It's not just the government trying to support the corn farmers.

The limit for ethanol in standard pump gas is 10% ethanol per gallon of gas. Not all base stock gasoline starts life with the same octane ratings. Some gasoline is higher some gasoline is lower prior to anything being added to it. So if you are trying to make a 93 octane fuel and already have 10% ethanol added you will have to use the other octane boosting additives to achieve the desired result. The refineries will use the cheapest additive they can find at the time the gasoline is being produced. Some weeks this will be "X" additive, for other weeks it will be "Y" additive. This may or may not be cheaper than ethanol but regulations say at least some ethanol has to be used because of its environmental benefits.

Here is the major draw back to using octane boosted fuels if you don't need to. There is less pure gasoline per gallon in higher octane fuels. The octane boosting compounds used in the fuel do not contain the same energy density as gasoline. So 93 octane fuel has less BTU's per gallon of fuel than 87 octane fuel. In other words a car that can run on 87 octane fuel will get more miles per gallon then if you ran it on 93 octane fuel.

If I get more GPM on 87 octane fuel than 93 octane fuel than why even bother with higher octane you ask? That answer gets a little technical but the short and sweet of it is that higher compression engines are more efficient. So even though your fuel has less energy the engine is able to turn more of the available energy into work.

Another side benefit of the octane boosting additives is that they often times are very good detergents for cleaning deposits out of your fuel system. That's why marketing people claim their premium high octane fuels "clean" your engine. Products like fuel injector cleaners and fuel stabilizers (like sta-bil) contain a lot the same chemicals that fuel refiners use to increase octane in fuels.

I'm not promoting the use of one fuel over another. In personal use I exclusively use 93 octane premium fuel in my small gasoline engines. I pay the extra price per gallon not for the extra octane rating but for all the additives the fuel refiner has already added to my fuel so I don't have to. I never use any stabilizer products in my fuel and never have issues with carburetors. I'm also very lazy when it comes to storing my equipment in that I never drain the fuel from tanks or carburetors. It works for me and I never have issues starting equipment even after it has sat for over a year with the same fuel in it.
 

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Keep in mind the true meaning of the octane rating. The octane rating, or number, only indicates the ability of the fuel to resist self detonation at higher combustion ratios.

Four cycle engines compress the air and fuel mixture within the cylinder prior to ignition. Creating more HP within the engine is a function of pushing as much fuel air mixture into the cylinder as possible prior to ignition. More compression equals a more powerful explosion within the cylinder, however, by using lower octane rated fuel you can also lose HP to pre-ignition, the self detonation of the fuel prior to the designated point of ignition specified by the manufacturer.

An engine whose compression ratio is 8:1 will run almost any gasoline down to the lowest octane, and that engine will run properly. An engine with a compression ratio at 10, 11, 12:1 will require higher octane rated gasoline. However, it is not the fuel creating the additional horse power, it is the higher compression ratio creating a more powerful explosion.

Q: If that is the case why is it that diesel engines, which use very low octane fuels, and have generally higher compression ratios, not pre detonate?
A: Because the fuel is injected AFTER the air in the cylinder is compressed.

Q: In layman's terms which octane rating is the most "efficient".
A: The lower octane fuel which is more explosive, cleaner running, and requires less fuel to create equal horsepower in lower compression engines.

Q: Then why don't high powered engines use lower octane rated fuels.
A: Because to create horsepower more fuel at higher compression ratios is a major part of the horsepower formula. As stated above the fuel would pre-detonate usually resulting in less horsepower, hence the need for the higher octane rating.


Myth: Higher octane rated fuels are better for my car. Period.

False. Use what the manufacturer recommends based on the compression ratio.


From WIKI;

"The other rarely-discussed reality with high-octane fuels associated with "high performance" is that as octane increases, the specific gravity and energy content of the fuel per unit of weight are reduced. The net result is that to make a given amount of power, more high-octane fuel must be burned in the engine. Lighter and "thinner" fuel also has a lower specific heat, so the practice of running an engine "rich" to use excess fuel to aid in cooling requires richer and richer mixtures as octane increases. "

"Higher-octane, lower-energy-dense "thinner" fuels often contain alcohol compounds incompatible with the stock fuel system components, which also makes them hygroscopic. They also evaporate away much more easily than heavier, lower-octane fuel which leads to more accumulated contaminants in the fuel system. Its typically the hydrochloric acids that form due to that water and the compounds in the fuel that have the most detrimental effects on the engine fuel system components, as such acids corrode many metals used in gasoline fuel systems. ""
 
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