How To Winterize Your RV Generator And Keep It Running For Many Years To Come

Leaving mechanical things untouched for a long time is never a good idea, especially if we’re talking about your RV generator. You’ll encounter all sorts of problems such as corrosion, varnished fuel and a clogged carburetor.

Obviously, these are the kind of problems you want to avoid. That’s why winterizing your RV generator is super important.

Let’s get started, shall we?

I’m by no means a professional mechanic. This article is based on research.

Step one: making sure your fuel tank is filled with the appropriate fuel

After about 30 days of inactivity, condensation will form, which will result in corrosion and other issues. By making sure your tank is completely full, you reduce the risk of water vapor that can condense and contaminate fuel forming on the sides of your fuel tank.

So how do you do this? Simply run the fuel tank low just before storage and then fill it with the appropriate fresh fuel. Not all gas is the same. There are many specifications, and you should use the one recommended in your generator’s manual if you want a reliable generator.

Black plastic cap of aluminum gas tank in silver color with the inscription "DIESEL".


In your manual, you can find what fuel the company recommends. Let’s take this manual for example. In the chapter called “recommended fuel” they mention this:

“Diesel fuel specified by ASTM D975 or EN 590 are recommended. Use grade 1-D diesel fuel when ambient temperatures are below freezing. The fuel should have a Cetane number of at least 45 for reliable starting”

What are 1-D diesel fuels, ASTM, EN and cetane numbers?

1-D diesel fuel doesn’t contain paraffin (a type of wax), which allows the diesel to remain in liquid form during the winter months.

ASTM is an acronym for the American Society for Testing and Materials. They improve product quality, enhance health and safety and make sure customers can count on products. ASTM D975 is the Standard Specification that most states have adopted as their diesel fuel standard.

EN 590 is another specification that you often see in Europe. It’s the minimum requirement that all automotive diesel fuel must meet if sold in most of Europe.

A Cetane number is a measurement of the quality or performance of diesel fuel. The higher this number, the easier it burns within the engine.

So the best thing to do is look up the owner’s/operator’s manual of your RV generator and contact your local gas station to find out if they have the appropriate type of diesel. Here are some links that take you to manuals of popular brands:


Biodiesel is generally not recommended for generators due to two main reasons:

  • Unlike traditional diesel fuel, biodiesel is pretty corrosive, which is a no-no for your fuel system—including your fuel tank. It will often need to be replaced or cleaned.
  • Biodiesel contains more moisture, increasing the risks of microbial growth.

If you want to use biodiesel, always consult your manual and see what it has to say. The manual in this example mentions that it’s okay to use B5 biodiesel as long as it meets industry specifications and quality. B5 means that the fuel contains 5% biodiesel and 95% petrodiesel.


If you have a generator that runs on gasoline, it’s best to use regular unleaded or gasoline with 10% ethanol (E10) or less. Check your manual to be sure, it may also allow you to use gasoline with 5% methanol.

orange and white gas pump

Propane (LPG) Generators

If you take a look at the operator’s manual of the QG 2500 LP generator, you can see what fuel they recommend for LPG models:

“Use clean, fresh commercial propane or HD-5 grade liquid propane gas in a mixture of at least 90 percent propane.” This is the most widely sold type of propane in the US market so you shouldn’t have any trouble finding it.

Closeup man's hand operating valve of LPG cylinder

Step two: use a fuel stabilizer

If you leave your fuel alone for as little as 30 days, both your gasoline and diesel will start to degrade. Gasoline will varnish and diesel will start growing mold and gel in cold weather. Propane on the other hand, doesn’t go bad.

So if you have a generator that runs on propane (LPG), you can safely skip this step and the next one as well.

Diesel and biodiesel

To stabilize your (bio)diesel, I’d recommend using STA-BIL Diesel Fuel Stabilizer. It does exactly what you need it to do:

  • Lubricates your fuel system
  • Protects against corrosion
  • Reduces oxidation of diesel fuel
  • Helps remove water that bacteria, fungus and algae require to grow

About 1 ounce per 5 gallons keeps your fuel safe for 24 months. After that, they recommend either using or draining the fuel. Using more than recommended won’t enhance or weaken the effects.


I’d recommend using Cummins STA-BIL Gasoline Fuel Stabilizer. It’s designed to prevent gasoline breakdown during extended RV storage. It protects gasoline against varnish, gum and corrosion, which is exactly what you need.

There are so many great fuel stabilizers, this is just one of them. Feel free to choose one yourself. Just make sure it does the job.

What if your fuel is already degrading?

If you discovered this article too late, it could be that your fuel is already varnishing, gumming or growing fungus. A fuel stabilizer won’t be of much use at this stage. You need to clean the carburetor with a carburetor cleaner.

If you want to clean your carburetor properly, it will take you some time. For instructions on how to do this, watch the video below.

Step three: run your generator at 70% of its maximum load for 30 minutes

The point of this step is to get the fuel stabilizer in every line and engine component of your generator.

The load of your generator is the maximum power it can deliver. This power is measured in watts. Common load values are 5000 watts, 4500, 4000, 2500, 2000 and so on. You can usually find it printed on the front or back of your generator. If not, check the manual of your generator.

So if you have a 3000-watt generator, you’ll need to draw about 2100 watts for 30 minutes. Something like a heater will do the job. Just use this page to check the average wattage of common electrical devices.


a 950 watt generator

Step four: change the oil and filter

Changing your oil and filter will prevent the build-up of acids that could corrode the bearings inside the engine.

Get your manual ready because you’re going to need it. Use only the oil recommended in the manual. Look for a chapter called “recommended engine oil” or something like that. I’ll use this Cummins Onan manual once more as an example.

A red funnel with a container of engine oil

API and oil categories

The manual recommends using API CH-4 oil or better. API is an acronym for the American Petroleum Institute. This is the largest oil and gas industry trade organization. Since some oils are not suitable for certain engines, they made a classification system. That’s why you need to consult your manual and see what the manufacturers recommend.

This manual recommends using CH-4, so what’s that? It’s one of the many diesel categories. It’s an oil that was introduced in 1998 and is one of the oldest oils still being used for diesel engines. Since the manual recommends using CH-4 oil or higher quality, you can also use CI-4, CJ-4 or CK-4. However, if you run your generator on gasoline, you’ll need another classification. This page shows you all the oil categories.

Viscosity grades (SAE)

Then there’s one more thing you should know before you can buy the right oil—the viscosity grades (SAE). If you’re going to buy oil, you’ll notice numbers such as 5W, 40, 15W-40, 20W,… These are other classifications based on the flowability of the oil.

Engine oil Shell 10w-40.

Since the thickness of motor oil is affected by temperature, the grade indicates whether the oil is usable at certain temperatures. Most manuals of generators share a chart like this one:

A graph that shows the viscosity grades with their suitable temperatures.
Note: this chart may look different in your manual.

So for this example, I suggest you use oil with a viscosity grade of 10W30 or 10W40 if it’s not going to be colder than 0°F. These are examples of multigrade oils and can generally be used throughout the whole year. Monogrades like 30 perform better at high temperatures but worse at low temperatures.

If you want to learn more about viscosity grades, check out this article.

How to change your oil and oil filter

Fortunately, changing your oil and its filter is not as complicated as figuring out what oil you need. The video below gives you the necessary guidelines. It may look a bit different with your generator, but it’s the same concept. Here’s what you’ll need to do in short:

  • Locate your oil plug, filter and your oil fill cap.
  • Remove your oil plug to drain the oil. You may need to use a funnel as shown in this video.
  • Change the filter.
  • Put in some fresh oil.
  • Run the engine for a few minutes.

Also, you should know that it’s recommended to change your oil every 25-50 hours of use. This information can usually be found in your manual.

Step five: Fogging your gasoline-fueled generator

Fogging oil prevents rust build-up by applying an oily coating. If you want to fully protect your generator, it’s recommended that you fog the cylinder walls and piston rings.

So how do you go about doing this? Just follow the instructions in this video. Here’s what the video recommends doing:

  • Locate and remove the spark plug with:
    • A spark plug wrench
    • A socket extension
    • A ratchet
  • Spray two one-second squirts into the cylinder.
  • Set your engine switch to OFF. You want to make sure that there’s no ignition because this will burn the fogging oil.
  • Pull the starter string a few times to circulate the fogging oil throughout the generator.
  • Spray one more one-second squirt in the cylinder.
  • Make sure your spark plug isn’t damaged or rusty. If you notice corrosion or damage, get yourself a new spark plug. However, finding out which one you need can be a pain in the ass. If you can’t find this information in your manual, you may want to contact the manufacturer of your generator.
  • Apply a very thin coat of anti-seize lubricant.
  • Carefully reinstall your spark plug (it’s easy to damage the threads).

A very rusty generator

Step six: cleaning your air filter

While this is an optional step, your air filter needs cleaning once in a while. If your filter is too clogged, you can expect poor performance and permanent damage. Cleaning your filter every 50 hours of use should be sufficient.

It’s a very easy task and shouldn’t take you longer than 10 minutes. All you need is some oil, water and soap. Watch the video for instructions.

Step seven: check if all cables and wires are still connected and protected

There’s not much to say about this step. Just make sure there are no loose hanging cables or wires, and that each nut is screwed in place.

Step eight: disconnect your battery to prevent battery drain

To fully eliminate battery drain, you can simply disconnect the battery. I found a video on how to change the battery of a Generac generator. You can use it as a guideline to disconnect your battery.

a car battery

Step nine (Optional): exercising your RV generator

This step is not really necessary if you’ve done everything up until now, but if you want to get the most years out of your generator, this step will definitely help you. Periodically running your generator runs oil through passages, forces the parts to move and drives off moisture. All in all, a healthy generator is one that gets to run.

This is a pretty easy step. Let’s take our manual again and see what it has to say. You should notice a chapter called “practicing the generator set” or something like that. In this case, it recommends running the generator for at least 2 hours per month at 50% of its load. So if you have a 4000-watt generator, you’ll need to draw about 2000 watts. You can easily achieve this with a dishwasher or two irons for example. Just use this page to check the average wattage of common electrical devices.

Final words

Preparing your RV generator for storage takes some time, but it’s necessary if you want to get the most out of it. It will significantly increase the lifetime of your generator and spare you a whole lot of trouble.

I hope that this guide was of use to you as a newcomer to engines and generators. Let me know in the comments how it went!


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