Mountfield SP185 Self-propelled Petrol Lawn Mower

Mountfield SP185 Petrol Lawn Mower: £254*

*Price correct from B&Q at time of publishing

 

 

Tested April 2026

Mountfield have kindly sent me a mower to try and I’d asked for a few must haves: self-propelled, either mulching or collection and no narrower than 46 cm. I was happy to try either petrol or battery powered and they sent me the petrol version. This mower is intended for cutting medium  to large sized lawns, up to about 1500 square metres.

First impressions:
The mower arrived in a large box, so I already knew it would need assembling before use. The process was straightforward: the handlebars needed unfolding and tightening with the supplied bolts, the wheels had to be slotted on and secured, and the grass box needed assembling by simply pushing the material section into the clips on the box. Nothing was complicated, but it did take a bit of time and a basic set of tools, and once everything is secured the mower feels properly put together and almost ready for use.

Don’t forget you’ll need SAE30 oil for the engine, as well as petrol. I needed a small funnel to get the oil in, because the filler hole is quite narrow and situated lower down on the side of the engine rather than being a large top fill type.

The mower feels solid, with a robust steel deck that is powder coated in Mountfield’s traditional red. The wheels are made from a hard plastic material, but I’m happy to assume they’re hard wearing. The handles are comfortable to hold, even though there’s no extra grip or padding.

Power comes from a 139cc Stiga ST140 Autochoke OHV engine. I’ve used Mountfield mowers with Briggs & Stratton engines before but I haven’t tried a Stiga powered Mountfield, until now. The engine looks the business and if their battery powered tools are anything to go by, it should be high quality.

Mowing and performance – collection of clippings:
For the first cut of the year I wanted to collect the clippings, so I fitted the 60 litre collection box to the back. It drops onto a couple of plastic lugs on the mower and is very easy to put on and remove.

I set the cutting height slightly higher than I’d usually cut for the main season. The grass wasn’t long, but it was varying in height throughout the gardens and that first cut always smartens up the lawns and gives an overall level. The six position height adjuster is one of the most user friendly features on the mower: some machines need all four wheels adjusted individually, on others the lever feels stiff and heavy when lifting the cutting height. The SP185 has a single lever that changes the height for all wheels in one go. The action is really easy and smooth, so you can quickly switch between a close mown finish and a slightly longer cut without needing to wrestle with each wheel.

There’s no primer bulb on this engine, as it has an autochoke. With the dead man’s handle pulled in I gave a good pull on the starter cord and the mower fired up first time, which was very pleasing.

I pulled up the self propelled drive handle and we were off! It moves at a really good, easy pace, so you’re more guiding than pushing, which makes a noticeable difference if you’re covering large areas or working for any length of time. The 46cm cutting width and manageable weight give it a good balance between progress and manoeuvrability and it still feels easy to handle in tighter spaces. For areas that require more control you can simply let go of the self propelled handle and control the speed yourself. It did a lovely job cutting; there’s a skid plate on the underside of the deck which reduces scalping of the lawn but as I was cutting slightly higher this wasn’t an issue. The box collected well and it has a bag full indicator to show when it’s time to empty rather than having to guess.

Mulching option:
The mulching plug lets you cut the clippings very finely and return them to the lawn as a light feed, which is useful on established lawns where you want to recycle a bit of organic matter.

To use the mulching option the collection box needs to be off the mower. The mulching plug is provided and is very easy to put in place: lift the flap at the back of the mower, guide the plug in and drop it down into position. When the flap drops back down it will now sit slightly open, so that the clippings are fired down towards the ground.

I tend to mulch only on warm and dry days so that the clippings don’t lie wet on the surface. Luckily we’ve had some lovely warm days, so I was able to put it to the test. I found that it worked really well, with the clippings returned evenly to the lawn so they can barely be seen. This is definitely something I’ll be doing throughout the summer months.

Practical points and handling:
The handles are comfortable, height adjustable and fold down for storage, which makes a real difference in a shed like ours where every inch of space matters. The self propelled lever is easy to engage and disengage, and you can quickly drop back to 'push only' when you are working in tighter spots. The recoil start system is straightforward and easy, and the engine is neither overly loud nor excessively rough over a normal working session.

As with any petrol mower, a bit of routine care pays off. Emptying the grass box, clearing the deck, keeping the blade sharp and checking the oil regularly will keep the SP185 cutting cleanly and starting reliably. The two year manufacturer warranty and the wider Mountfield/STIGA support network also give some of peace of mind if you ever need to call on a local dealer.

Having used many different mowers in my time at Barnsdale, I still rely on rotary roller machines for the areas where I like a clear striped effect. For all the other lawns where stripes aren’t required, the SP185 will be my go to machine. It is particularly well suited to our orchard area, where fruit trees sit within a grassed lawn and there are plenty of trees and beds to cut around. The combination of self-propelled drive and manageable size makes it ideal for these more intricate spaces.

Verdict:
If you are looking for a capable, self-propelled petrol mower for a medium sized lawn, the Mountfield SP185 is well worth a serious look. It is not a lightweight toy, but a properly built machine that allows you to cut efficiently and comfortably. For gardeners who want a straightforward, no-nonsense mower that can cope with regular use and still make the job feel less of a chore, particularly if you do have any slopes in your garden, the SP185 self-propelled version has earnt a solid place in our machinery shed.

 

We test a wide range of garden tools and machinery at Barnsdale Gardens to help you choose the right equipment for your garden.