Petrol vs Diesel pressure washer comparison against lightning bolt background

 When our customers contact us regarding our pressure washers, one of the most common questions asked is “What is the difference between a diesel or a petrol pressure washer?”. In this post we’re going to discuss the differences of petrol and diesel pressure washers, weighing up the pros and cons of each in order to help you decide which is the best option for you. 

The visual differences between petrol and diesel pressure washers

The simplest place to start is to compare and contrast the visual differences between our range of diesel and petrol pressure washers.

All of our diesel pressure washers are mounted on a wraparound heavy duty steel chassis with four pneumatic tyres. The visual style of a petrol pressure washer however, depends on what range you go for. Our KIAM Warrior range, for example, are similar in look to our diesel range in that they adopt the heavy-duty steel chassis, however, they differ in the fact that the Warrior petrol range has two pneumatic tyres instead of four.

Our KIAM KM range of petrol pressure washers differs completely in look to the previously mentioned range of pressure washers. The KM range utilises an open top heavy-duty steel frame attached with two pneumatic tyres and two front rubber absorbers.

\difference between petrol and diesel pressure washers comparison against a blue background

Weight differences between petrol and diesel pressure washers

Another factor to consider is the difference in weight between the petrol and diesel pressure washers.

Petrol pressure washers are typically lighter in comparison to their diesel counterparts. The average 13 horsepower (HP) petrol pressure washer for example, weighs roughly 68kg with the equivalent diesel pressure washer weighing roughly 100kg.

The reasons for the difference in weight is due to the diesel pressure washers operating on a heavier key start engine, containing a battery and an accompanying alternator trickle charge. The petrol pressure washer is typically a pull recoil start and they are, therefore, smaller and lighter.


The fact that the diesel pressure washer uses four pneumatic tyres means that despite carrying a few extra kilos, they are still extremely easy to push around on all types of surfaces.

This easy manoeuvring can also be said for our range of petrol pressure washers. The lighter petrol pressure washers make use of two pneumatic tyres, which again, make it quick and easy to reposition. One of the slight differences is that the Warrior petrol pressure washer range comes with a drop-down handle which makes the unit more compact and as a result, easier to fit into your vehicle.

Area of Use – Residential or Commercial?

Our range of petrol pressure washers tend to be the preferred choice for those carrying out the majority of their work in residential areas. This is because the petrol pressure washers have a lower noise output

The diesel pressure washers are slightly louder than the petrol pressure washers, and as a result, they are often used by those working mainly on larger commercial jobs or on site.

Diesel and petrol pressure washer maintenance

Both the diesel and petrol range of pressure washers need some tender love and care, but the diesel range is definitely the more needy out of the two! A petrol pressure washer contains a spark plug and HT lead, and you will only need to change the engine oil, clean the spark plug and replace the air filter every so often. In comparison, a diesel pressure washer needs its engine oil changing every 50 hours (roughly) and the diesel injectors and air filters need replacing too.

Photograph of man performing maintenance on his petrol pressure washer

Reduction gearbox’s

Whilst this section is not a direct comparison between diesel and petrol pressure washers, it is an important factor to consider before you choose which pressure washer to purchase. We have a range of standard petrol and diesel pressure washers (identifiable by the P or D after the item name e.g., KM3700P is a petrol and KM3600DX is a diesel).

These petrol washers are fitted with a direct drive pump; the pump is directly coupled with a shaft on the engine. This means that the Revs Per Minute (RPM) of the engine will be equivalent to the RPM of the pump. In addition, we have a range of pressure washers fitted with a 2-to-1 reduction gearbox (identifiable by the PR or DXR after the item name e.g., KM3700PR is a petrol with reduction gearbox and a KM3600DXR is a diesel with reduction gearbox).

This means that the engine and pump on a pressure washer fitted with a 2-to-1 reduction gearbox will differ by half. If the engine on a pressure washer, fitted with a 2-to-1 reduction gearbox, is 3000 RPM then the pump will be turning at roughly 1450RPM. By reducing the rate of RPM, the pressure washer gives two main benefits. Firstly, the pump will have a longer life span and secondly, running at a lower RPM provides the option of easily sucking water from a standing water source, ideal for those jobs where a customer has low water pressure or no outdoor tap.

Still need help? Contact our experts!

You can browse the product specifications on our different models in our Petrol Pressure Washer Collection and our Diesel Pressure Washer Collection for more information, or for more advice on choosing your pressure washer, get in touch with our experts today on 0151 548 5500, or drop us an email on Our team are more than willing to help you find the perfect pressure washer for your needs.

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