Generator Fuel – What are the Options?
Have you ever researched generator fuel? Generators do not all use the same fuel. While the majority of them use the same gasoline that you would put into a car or a lawnmower, that is not the case for all of them. This is not an exhaustive list of generator fuels, but the most common options.
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2 Stroke Generators
2 stroke generators refer to the combustion cycle that they use, which is a simpler cycle with only 2 strokes, as opposed to the much more common 4 stroke cycle. These used to be much more common, since it is a simpler design, but as technology has progressed, it has become easier to make more complex designs. For various technical engineering reasons, it is often easier to make very small engines 2 stroke, but above a certain size, it is easier to make them 4 stroke.
2 Smoke (actually 2 stroke) generators use a combination of a special oil and gasoline, mixed together. Some of these will allow you to put them in separate compartments and mix them on their own, but most will require you to pre-mix them at a specific ratio. It actually lubricates itself with this oil, with a “total loss” lubrication system.
The advantage of these is that there is no oil to change and that they tend to be less expensive upfront than an equivalent sized 4 stroke. They are fairly robust generally speaking, and tend to be compact.
The disadvantage is that they typically produce a fair amount of noise for the size and that since they are literally burning oil in order to run, they smoke more than an equivalent 4 stroke engine. As a result of this, the EPA has banned most new 2 stroke engines, which has made them much less common. Modern 2 stroke engines are not anywhere near as bad as old ones, but it is still worth noting.
You have to keep a special fuel additive (the oil) on hand, and usually have to keep a special container on hand for the pre-mixed mixture. It is not hard to mix, but it is an extra step, and if it is after dark when a power outage hits, it can be an extra step that is a pain in the rear.
Because 2 stroke engines run on gasoline, just as with 4 stroke gasoline and diesel, you will have to occasionally run the generator to make sure the fuel does not go bad inside of it. If you do not, it can require extensive repair work, since the fuel itself will turn into varnish inside the generator, clogging all sorts of things, and making it impossible to run.
I recommend these as an option if you are extremely budget-conscious, but require a new generator, AND you are already familiar with mixing the fuel for 2 stroke engines. Alternately, if this is just a backup or more portable power source that you are not absolutely depending on, they can be worth experimenting with.
On a fun note, there are 2 stroke oils that smell of different substances when you run them through your engine. I have some that make my chainsaw smell like strawberries or coffee whenever I run it, and watching people try to figure out why my work area smells like a pre-teen girls lip gloss is hilarious.
Gasoline (also Referred to as 4 Stroke)
4 stroke engines are what you are probably used to using- most cars, most lawnmowers, most motorcycles, and especially of note for this, most generators.
The biggest advantage to 4 stroke is the availability and ease of use. The majority of generators are sold as 4 stroke engines, both in the US and on a worldwide basis. They use the most common form of internal combustion engine fuel, and if you can operate a gasoline lawnmower or similar power equipment, you can generally operate it easily.
If you keep gasoline on hand for your car (or lawnmower, or modern weed whacker, or motorcycle, or any one of a number of other things) you will be used to storing fuel for this kind of generator. As I cover later, storing it with a fuel stabilizer is a great idea. The advantage of having a fuel that you can purchase at the corner gas station is immense, and if you have to be mobile during a bug out, this may be your best option.
4 stroke gasoline engines also have the advantage of parts availability- depending on the brand, the parts can be extremely easy to get. Honda generators are typically reasonable to get parts for, even older ones, and there are a lot of Honda clones (machines that use the same pattern but are not made by Honda) on the market from China.
The biggest disadvantage? Fuel. Gasoline goes bad over time and actually clogs things up. Even with fuel stabilizer, it is only good for a couple of years of sitting there. There are other fuel types that share this weakness, so it is not necessarily worse than those are.
If you rely on your generator in emergencies, and like most people want it to sit there happily until there is an emergency, and run it then, you can be in serious trouble because the fuel has gone bad.
Since it requires a lot more than just emptying out the old fuel and putting in new and it will have clogged the internal parts of the generator when you let it sit for too long, it is easier to maintain than to repair. The best way to prevent this is to regularly run the generator, which both keeps the fuel from going bad as quickly and helps to maintain the internal parts of the generator, keeping it in working order.
Assuming you keep up on running it as often as you should, it still requires regular oil changes- trust me, if you want your generator to last, these are not optional- and so when you run your generator, you have to keep track of the hours, and replace the oil often enough. Given that an inexpensive poorly designed generator can actually be a real pain in the rear to change the oil on (nicer generators tend to be easier to work on) a lot of people will skip on oil changes, or just straight forget. The oil changes are not terribly frequent, but that just adds to the problem, since people forget to do them.
On the other hand, if you do not use your generator very often, you may be better off just using the calendar method- Oil actually degrades into an acid over time, which is why you are supposed to change your oil every “3000 miles or 3 months”. Modern oils are not as prone to this, so just planning to change your oil once a year if it needs it or not may be your best bet, since it is less hassle than keeping track of hours.
All that said, if you are expecting to use your generator on a regular basis, are willing to add fuel stabilizer every single time you put it away and keep up on the oil changes- 4 stroke generators are common and relatively inexpensive, and offered with a huge number of features to choose from, with many brands as options. These tend to be fairly user-friendly, easy to operate, and very common for a reason.
Propane (my favorite)
Propane generators are actually a 4 stroke engine that runs on propane instead of gasoline- I covered gasoline 4 strokes, so this is mostly the difference between them.
Propane does go bad, but not in the lifespan of human civilization. It will take hundreds of thousands of years before propane actually degrades into a nonusable fuel. If you have propane for that long, and it goes bad, and you can find me, I will offer my public apologies for suggesting the fuel and saying that it does not go bad. Right after I take notes on time travel or immortality.
When you store propane for a generator it is typically stored in canisters (also called tanks) that are designed for long-term storage, with a 5-gallon “Barbecue Tank” being the most common size. If propane spills, it dissipates into the atmosphere, instead of soaking things and causing even more of a hazard. Propane does not give off fumes just from being stored properly, and while it is dangerous to inhale, propane canisters come with safety devices built into them to make it hard to accidentally do so.
My rule of thumb is to store it out of direct sun, not in an airtight area, and not in an area with living beings. A shed in the backyard with a side that shades the ground in the afternoon is just about perfect. If a fire marshal or similar contradicts me, listen to them.
Basically, propane is much easier to store than gasoline, and because it does not go bad, if you run a generator on it the generator does not have clogged fuel lines and a clogged carburetor the next time you need to run it.
On the downside, propane is less energy-dense than gasoline- you can expect to downgrade the capacity of a generator by around 20% if you are running it on propane rather than gasoline. Yes, I am aware that propane is not exactly 20% less energy-dense than gasoline, but the flow rate of the fuel is different enough to make up for it. Different generators will have different rates of efficiency, so this is just a general rule of thumb.
Also on the downside, propane is not as available in most places as gasoline- storing enough fuel for more than a brief power outage may be an issue. I keep several propane tanks on hand since my preparations include using it to cook food and to heat my home if needed, but that may not be the best choice for everyone.
My duel fuel generator runs for about four to five hours on a tank of gasoline and about six to eight hours on a 20 lb propane cylinder, leading to similar fuel costs. I keep enough propane on hand for 72 hours of heavy use, and since I don’t have to turn over my fuel storage, I can more or less just let it sit there.
I actually really like dual fuel propane gasoline generators- I have one that I keep handy, and when I need to run it, I use propane with it, meaning that I don’t have to worry about most of the storage issues I would have with gasoline. It is not notably larger or more difficult to run than a single fuel generator, and if I ever have to run gasoline in it, I can.
On the occasion that I run gasoline with it, I make sure to run it completely out of fuel before storing it, adding a fuel stabilizer to the gasoline before running it out. When I run gasoline in it after I have not for a while, I like to run a fuel system cleaner in it, such as Seafoam, and that seems to clear out any clogs that form.
Diesel
Diesel generators are typically going to be fairly large, just due to the nature of diesel engine efficiency. Because of that, most of the diesel engine generators that a homeowner will deal with will be for whole-house backup generators.
Diesel generators tend to be fairly reliable, and require less maintenance per generator hour than gasoline generators do.
Unfortunately, they cost in proportion to their reliability, and you have to source the fuel for it separately from a gasoline engine- it tends to be no harder to source than propane is, however, but it has all the storage drawbacks of any liquid fuel. On the other hand, Bio-Diesel is a thing, as is running diesel generators on old oil that has been filtered through dirty socks, so in a long-term emergency, diesel can be a great option.
Just as with gasoline, diesel-fueled generators will require occasionally running the generator in order to avoid damage from fuel sitting for too long.
I would recommend these if you have a diesel truck, and will remember to run the generator regularly.
Alcohol
Straight Alcohol is not to be confused with E85 (occasionally called boozaline), which is actually a blend of 85% ethyl alcohol mixed with additives so that people cannot drink it. E-85 can be difficult to find, however, and where I live (a city of around 100,000 people next to a similar size city and a major university where I live), there are only 3 E-85 fueling stations last time I looked.
Alcohol was actually used as an alternative fuel to gasoline for the model T- it came with factory options that allowed it to burn ethanol so that farmers could make their own fuel. As an alternative to Gasoline (or other petroleum products), it is still used around the world as a fuel. Brazil for example uses it as a way to help achieve energy independence.
While I am not aware of very many generators on the market meant to run straight ethanol, there are conversion kits that replace internal seals and such that would be damaged by running ethanol normally.
The biggest single advantage to E85 and straight ethanol generators is that in a long-term disaster, you can theoretically create your own fuel. Additionally, straight ethanol should not go bad in the tank, since it is actually used as an additive to keep fuel from going bad.
Natural Gas
An honorable mention- Natural gas. Natural gas has most of the advantages of propane but is generally not stored like propane is. Natural gas is usually available as a direct pipeline from your local utility however and is a popular choice as a fuel for whole-house backup generators. If there is a major earthquake, it can disrupt natural gas lines, however.
If you own a CNG car, or you have a CNG compressor on your home in order to fuel your car, it can make a great deal of sense to have a natural gas generator, since you can arrange fuel storage for your generator.
These have enough quirks that they can use their own article to explain it all, but I recommend looking into them for whole house backups if natural gas is available in your area.