Best Honda GX390 Pressure Washers of 2026 (4000 PSI Powerhouse)
A Honda GX390 pressure washer is a gas washer built around one of the most common commercial engines in the business: a 389 cc, single-cylinder, air-cooled, four-stroke motor. Honda rates it at about 11.7 horsepower, and that is enough to drive a pump making 4,000 PSI at 4.0 GPM. This guide explains what the engine does, which washers use it, and what to check before you buy one. It is not a list of every machine with a Honda badge. Some well-known 4,000-plus PSI washers use other engines, and we say which ones. We also did not test any machine here. Specs come from maker sheets and dealer listings, and we flag every place where sources disagree. Why you can trust this guide Source order. We used maker spec sheets first, then dealer and parts listings. Each section says which one it relied on. Corrections. An earlier version of this page listed a Simpson “Aluminum Series 4,400 PSI” washer. We could not find that model. Simpson’s own sheet for the Aluminum Series ALH4240 shows 4,200 PSI, so this page now uses that number. Gaps we could not close. We could not open Honda’s own GX390 manual, so we do not quote exact service intervals. Where the engine data differs between sources, we show the range. Last checked: October 24, 2026. Model codes and prices change, so confirm them with the seller. Honda GX390 specs at a glance Several dealer and distributor pages agree on the core numbers. Honda itself uses these ratings, and the small differences below come from how each seller rounds them. Spec Honda GX390 Engine type Single-cylinder, air-cooled, four-stroke, overhead valve Displacement 389 cc (88 mm bore x 64 mm stroke) Power About 8.7 kW (11.7 hp) at 3,600 rpm; some listings show 8.2 kW (11.0 hp) Torque About 26.5 N·m (19.5 lb-ft) at 2,500 rpm Compression ratio 8.0:1 or 8.2:1, depending on the source Oil capacity About 1.1 L (1.16 US qt) Fuel tank About 6.1 L (6.4 US qt) Dry weight About 31.5 kg (69 lb) Why a 4,000 PSI washer needs an engine this size You can check the match with a simple formula. The power water carries is PSI times GPM divided by 1,714, and the answer is in horsepower. A washer making 4,000 PSI at 4.0 GPM needs about 9.3 hp of water power. At 4,200 PSI it needs 9.8 hp. At 4,400 PSI, 17,600 cleaning units, it needs about 10.3 hp. No pump is perfectly efficient, so the real engine load is higher. That is why makers use an engine rated near 11 to 12 hp for this class. A smaller engine would be overloaded, and a much larger one would add weight and cost for no gain. The GX390 also has a long record in rental yards and fleets, which means parts and service are easy to find in most US towns. That matters more to a working crew than any single number on the spec sheet. What that power means in real work Compare it with a home machine. The RYOBI RY142500 is rated at 2,500 PSI and 1.2 GPM, which is 3,000 cleaning units. A 4,200 PSI washer at 4.0 GPM is 16,800 units, about 5.6 times as much. In practice that shows up as speed. A GX390 machine can clear wide concrete, truck beds, equipment and storefronts in far less time, and the 4 GPM flow carries loosened dirt away instead of just pushing it around. You can read how the smaller class performs in our RYOBI 2500 PSI review. Cleaning units are only a yardstick, calculated from maximum ratings. Nozzle size, hose length and how close you hold the wand all change the spray you actually get. Pressure washers that use the Honda GX390 These four machines pair the engine with a triplex pump. All figures come from maker or dealer listings. 1. Simpson Aluminum Series ALH4240 Simpson’s sheet for part 60688 lists 4,200 PSI at 4.0 GPM, a Honda GX390 and a CAT triplex pump on an aircraft-grade aluminum frame. Sources give the weight as 124 to 133 pounds, which is light for the class. It suits crews that load the washer in and out of a truck every day. 2. DEWALT DXPW60605 A parts listing gives 4,200 PSI, 4 GPM, a Honda 389 cc engine, a CAT industrial triplex pump and direct drive. The weight is 139 pounds. The same listing says there is no detergent injection, so plan on a separate soap method. Do not mix it up with the DXPW60606, which has different specs. 3. Pressure-Pro EB4040HC Dealers list 4,000 PSI at 4 GPM, a Honda GX390, a CAT 5PP3140 triplex pump, a 50-foot hose and a chemical injector. Prices run from about $2,177 to $2,212. The model name appears as E4040HC and EB4040HC, and some dealers sell both belt-drive and direct-drive versions, so confirm the drive type. 4. BE B4013 series BE sells several 4,000 PSI, 4.0 GPM models under this name, all with a GX390. The pump depends on the model: one sheet lists a General EZ4040G with a 50-foot hose and a 163-pound shipping weight, and another lists a CAT 66DX40GG1 with a 25-foot hose at 162 pounds. Read the full model code before you buy. Side-by-side comparison Model PSI GPM Pump Weight Simpson ALH4240 4,200 4.0 CAT triplex 124 to 133 lb DEWALT DXPW60605 4,200 4.0 CAT triplex, direct drive 139 lb Pressure-Pro EB4040HC 4,000 4.0 CAT 5PP3140 triplex Not listed BE B4013 series 4,000 4.0 General EZ4040G or CAT 66DX40GG1 162 to 163 lb (shipping) Not every big washer has a Honda GX390 Do not assume the engine from the PSI rating. The Simpson PowerShot PS60843 makes 4,400 PSI at 4.0 GPM, but it uses a 420 cc Simpson CRX420 engine. Kärcher’s HD 3.0/27 runs a Honda GX200, a smaller engine, and makes 2,700 PSI at 3.0 GPM. You will also see “GX390-compatible” or “13 hp” engines on very cheap washers. These are copies, not Honda
