Can I Put Mixed Gas in a Pressure Washer?

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A gas pressure washer is a fast and effective tool for cleaning your car, driveway, outdoor furnishing, and more. You can also use it to prep a surface for paint and remove dirt than a garden hose cannot. But it is only as good as the fuel that you put into it. Should you use mix gas? That is what we will explain here so you can avoid mistakes.

2-stroke pressure washers require a 50:1 or 40:1 mix of oil and gas. 4-stroke pressure washers have separate containers for oil and gas and should not be mixed. The best fuel to use for pressure washers is unleaded, 87 grade octane and 10% or lower ethanol.

Most pressure washers are 4-stroke so mixing fuel is not necessary. If your pressure washer is a 2-stroke model, mix the fuel according to the ratio given by the manufacturer.

Note: 2-stroke and 2-cyclle are used interchangeably, the same with 4-stroke and 4-cycle.

Why 2-Stroke Pressure Washers Need Mixed Gas

Just like a power tool running on gas – and pressure washers are power tools – you must use the right fuel for the best results. 2-stroke pressure washers are not as common as 4-stroke, but if you have one you need to use mixed gas.

A 2-stroke pressure washer runs on an oil/gas mix so the engine gets enough lubrication. The oil serves as lubricant, and without it the engine will overheat. The piston rings could come loose and the engine might stall.

The combustion chamber of a 2-stroke engine needs to be lubricated with oil. Most 2-stroke pressure washers to pressurize air and fuel into the combustion chamber. Unlike in a 4-stroke, the crankcase is not sealed in a 2-stroke engine. From the crankcase, the mixed gas goes into the combustion and burns.

In a 2-stroke pressure washer, the oil/gas mix and air are in the crankcase. So you have to lubricate the crankshaft otherwise the engine could overheat. Without oil lubrication, the pistons will not last long.

Why 4-Stroke Pressure Washers Do Not Need Mixed Gas

A four stroke engine does not need mixed gas because its crankcase is sealed. The fuel is on the cylinder while the oil is in the crankcase. There is no need to mix oil and gas because the oil goes into the crankcase directly.

If you use mixed gas on a 4-stroke pressure washer, it will produce a lot of smoke. Small amounts of mixed gas will not necessarily damage a 4-stroke. But if you pour a lot, it could cause serious damage.

A 4-stroke pressure washer is not supposed to be used with mixed gas. That is why it has separate compartments for these elements. Use the amount suggested by the manufacturer and you can avoid problems.

Does Your Pressure Washer Need Mixed Gas?

If your pressure washer is a 2-stroke, it needs a mixture of oil and gas. If it is a 4-stroke, the oil and gas must not be mixed.

The easiest way to tell if your pressure washer is a 2-stroke or 4-stroke is to look at the fuel tank. If there is only one, it is a 2-stroke. You pour the gas and oil into it using a 40:1, 50:1 or whatever ratio the manufacturer suggests.

If there are separate two tanks, you have a 4-stroke pressure washer. One tank is for the gas and the other is for the oil. There are also other ways to tell the difference.

  • Your owner’s manual provides information on what fuel to use. If it says combine gas with oil, the pressure washer is 2-stroke. But if you have to use separate tanks for the fuel, it is 4-stroke.
  • Check the fuel cap. The cap on a 2-stroke pressure washer has the mix ratio (50:1, 40:1, etc.). A 4-stroke cap does not.
  • Only 4-stroke engines have an oil fill cap. You can find this on either side.
  • Look for the label. There should be a 2-stroke or 4-stroke label on the engine.
  • Read the product description. Before you buy a pressure washer, check the product description. Even if it does not say it is 2 or 4-stroke, you will be able to tell by the fuel its engine requires.

Related. Is your pressure washer 2-stroke or 4-stroke?

What Type of Gas Do Pressure Washers Use?

Pressure washers use ethanol-free, unleaded gas with a minimum 87 octane rating. Replace the oil after 30 days to get the best results. The A-iPower APW2700C for instance, uses regular unleaded gas.

Unleaded gas works well with 2 and 4-stroke pressure washers. Unless the manufacturer specifically says you must use something different, unleaded gas is fine. Again keep in mind that 4-stroke engines do not mix gas and oil but 2-stroke engines do.

Figuring out what type of gas to use is not a problem. The owner’s manual will have that information. Or you can just go to the manufacturer website and enter the pressure washer make and model in the search box. Look at the specs and you will see what fuel it needs.

To be safe, just use unleaded gas and do not experiment. For instance, do not mix diesel with unleaded gas. If the pressure washer relies on unleaded gas only, do not put anything else there.

If you have a 2-stroke engine, follow the recommended mix ratio. Most use 50:1 but other pressure washers’ use 40:1 or even 33:1. Follow the ratio otherwise the pressure washer will not perform the way you expect it to. And as the owner’s manual will tell you, always pour the oil first followed by the gas.

The 87 octane rating is the minimum required. Refer to your owner’s manual if the engine needs a higher rating. As to what type of unleaded gas, obviously the higher the quality the better. As a rule, the gas you use in your car is good enough for pressure washers.

Safety Guidelines for Using Gas with Pressure Washers

No matter what gas pressure washer you use, the ethanol content must be 10% or lower. A bit of ethanol -10% or less – is fine for most pressure washers. But too much is going to be problematic.

Ethanol tends to draw water, and this can cause permanent engine damage. Rust builds up and spreads into the crankshaft, cylinders etc. Too much ethanol wears engine parts rapidly which means a shorter lifespan for your pressure washer. A solidly made product (the Generac 8874 2900 PSI pressure washer comes to mind) is also going to help.

Replace the fuel after 30 days. After four weeks or so, gas starts to oxidize and becomes unusable. Worse, the old fuel can spread rapidly throughout the engine and create a mess. Old gas will block the filters and you won’t be able to start the pressure washer.

The solution is to drain the oil after 30 days. Add new oil only after you have emptied the reservoir and cleaned it up.

Fuel stabilizers can minimize the effects of ethanol in a gas pressure washer. There are a lot of these products available so just look for one that is compatible with your model.

Never add fuel to a pressure washer indoors. You should store it outdoors and never put any flammable materials near it. Always make sure there is enough ventilation when adding oil.

Pressure washers are strong enough to remove paint. This is ideal if you want to get rid of old paint. If this is not what you want, use the white nozzle tip. That uses gentle pressure so you can clean car windows and other light surfaces without stripping paint off.
You can use premium gas but it is not required. It should work fine with most models but there is no need for it. Unleaded gas will do the job and there is no evidence that premium gas will improve performance, at least not enough to justify the extra cost.