The best spark plug lawnmowers, compared.
Top pick: Briggs & Stratton RC12YC pair – Score 96 from 4.8 and 2,482 reviews at about £7.99, an RC12YC pair whose pack-count cells disagree. Best value: NGK BPMR7A – Score 94 from 4.7 and 5,929 reviews at about £3.91, not the lowest price in the set. Updated October 2026.
A spark plug lawnmower part is the replaceable ignition piece in a small petrol engine. In the UK you usually meet one when a petrol mower or a related garden engine is hard to start. Match the code on the old plug or in the engine manual, not the word lawnmower in a title. Thread diameter, reach, hex size, heat range, resistor and electrode gap have to agree together. Flathead engines and overhead-valve engines do not share one plug. Short-reach two-stroke plugs for saws and strimmers are a third family. A 14 mm thread is not enough. The usual two-stroke pattern is a short reach with a 19 mm hex. Neighbouring heat-range numbers are not substitutes, and the letter R means a resistor. Take the gap from the engine chart after delivery. Many rows are 0.76 mm and some dated rows are 0.51 mm. Check or replace the plug if the engine will not start, about every 25 hours or once a season. Those checks are in the [spark plug lawnmower buying guide](/hub/lawn-and-garden-equipment/spark-plug-lawnmower/sub/spark-plug-lawnmower-buying-guide).
A spark plug lawnmower part is the replaceable ignition piece in a small petrol engine. In the UK you usually meet one when a petrol mower or a related garden engine is hard to start.
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Personal buying guide
Question 1 of 2
What does the old plug or the manual say?
Across 2,482 amazon.co.uk reviews at 4.8, this Briggs & Stratton listing is sold as an RC12YC pair at £7.99, with a 12-month warranty cell. UK reviews treat the plugs as a genuine service part and a spare in the same pack, including a first pull on a Masport and an easy fit on a Mountfield. One review says the terminal would not seat in a new coil boot that had already taken a Champion RC12YC. Another says the plugs were the wrong buy for an overhead-cam engine, which is a different layout from a typical overhead-valve Briggs. The title, the unit count and the included line say two plugs, while the Number of Items cell says 1, so count what arrives. The rank cell sits under car spark plugs, and this file does not print the 0.020 in gap used on some Quantum rows.
Pros
Cons
Best for: An OHV Briggs engine whose parts list calls for RC12YC, if you accept a pair and check the terminal in the boot.
Less suitable: A flathead engine, an overhead-cam engine, or a buyer who needs the Quantum 0.020 in plug. That gap is not in this listing.
Specifications
Common questions
How many plugs does the listing say are in the pack?
The title, the unit count and the included-components line say two BS-OHV plugs. The Number of Items cell says 1.
Which code is printed for this pair?
The title says RC12YC. The model cell is 992362 and the included line says 992304. The listing tells you to check the Briggs & Stratton parts list.
What do UK reviews say about fitting?
Reviewers report lawnmower use, including a first pull on a Masport and an easy fit on a Mountfield. One review says the terminal was too large for a new genuine Briggs coil boot.
The saved listing is a single NGK BPMR7A at £3.91, 4.7 from 5,929 reviews, the largest count in this set, and number 1 in Lawn Mower Spark Plugs on that rank cell. UK reviews mostly describe chainsaws, a Ryobi strimmer, a Stihl hedge trimmer, an FS55 and a Mitox blower starting after a change, with lawnmower servicing mentioned as well. One review says the built-in resistor was a poor replacement for a non-resistor CJ8 on a hand-pull saw. The Gap Size cell prints 9.5 mm and does not say whether that figure is the electrode gap or the reach. The unit count and a bullet say one plug, while the included-components cell says NO. The vehicle-type cell says Motorcycle, so the garden rank is not the same thing as a fit for a four-stroke mower.
Pros
Cons
Best for: A tool whose existing plug or manual says BPMR7A, especially a two-stroke saw or strimmer already on that code.
Less suitable: A four-stroke mower that calls for RJ19LM or RC12YC, or a saw specified as a non-resistor CJ8.
Specifications
Common questions
Is this a single plug?
The unit count is 1 and the bullet says one NGK BPMR7A. The included-components cell says NO.
What gap does the listing print?
The Gap Size cell says 9.5 millimetres. It does not say whether that figure is the electrode gap or the reach.
Where do UK reviews say it was used?
Named uses include chainsaws, a Ryobi strimmer, a Stihl hedge trimmer, an FS55, a Mitox blower and lawnmower servicing. One review says the resistor was wrong for a CJ8 on a pull-start saw.
This is a two-plug F6RTC listing at £5.59, 4.7 from 109 reviews, sold as a cross for NGK BPR6ES. A bullet states a 14 mm thread diameter and 19 mm of thread length, and the OEM line names MTD 951-10292 and 751-10292. UK reviews include a lawnmower and a 20-year MacAllister that started on the third pull with a 21 mm socket. One review says the plugs were not the ones in the photograph, though that reviewer still found the size right. The warranty cell says no, and a Universal Fit cell sits beside that specific part number. The vehicle-type cell says car and motorcycle, so you match the code and the stated 19 mm reach rather than the vehicle words.
Pros
Cons
Best for: A mower whose plug is already F6RTC or BPR6ES, and whose reach is the 19 mm the bullets state.
Less suitable: A short-reach two-stroke that needs 9.5 mm reach, or a buyer who needs the plugs to match the photograph.
Specifications
Common questions
What reach do the bullets state?
The bullets say a 14 mm thread diameter and a 19 mm thread length, and they name NGK BPR6ES among the crosses.
Did UK reviewers fit it to a mower?
Yes. One review names a lawnmower. Another says a 20-year MacAllister started on the third pull with a 21 mm socket.
Did the plugs match the photograph?
One UK review says the plugs received were not as pictured, and that the size was still right.
The saved listing is one NGK BPR5ES at £3.54, the lowest shelf price in this set, at 4.6 from 3,235 reviews and ranked 1 in Car Spark Plugs. UK reviews often say a Honda or other petrol mower started after the change, which is why the row sits in a lawnmower comparison at all. One reviewer bought it for a Mountfield S421 / ST100 and says that engine needs BPR6ES, not BPR5ES. Core and top cells say iridium, while the type name is NGK Genuine BPR5ES, and one UK review disputes the metal. One delivery arrived loose in an envelope, so the gap may have moved, and another review says only one plug arrived. The thread cell is M14 x 1.25, reach is not stated, and the origin cell says Italy.
Pros
Cons
Best for: An engine whose manual or old plug says BPR5ES, including some Honda mowers named in UK reviews.
Less suitable: A Mountfield ST100 or any engine specified as BPR6ES, and anyone who needs the electrode protected in transit.
Specifications
Common questions
Is this listed as a lawnmower plug?
The title is NGK BPR5ES. The rank cell is 1 in Car Spark Plugs. UK reviews in the file do describe petrol mowers, including Honda models.
What do the material cells say?
Core and top both say iridium. The item type name says NGK Genuine BPR5ES and does not say iridium. One UK review disputes the metal content.
Which UK review says the heat range was wrong?
One reviewer bought it for a Mountfield S421 / ST100 and says that engine needs BPR6ES, not BPR5ES.
A single Adefol cross at £4.74, 4.6 from 2,214 reviews, ranked 3 in Lawn Mower Spark Plugs on that cell. The bullets sell it against BPMR7A, L7T, CJ8, RCJ6Y, RCJ7Y and others, and they name 2-stroke kit in the 47 cc to 50 cc range plus Stihl and Husqvarna model strings. UK reviews often say a saw or strimmer started after fitting. The thread cell says M10, which does not line up with a 14 mm BPMR7A description, and one review says there is no resistor even though several codes on the list contain R. Gap and hex are not printed. The bullets offer a full refund if you are not satisfied, without stating how many months that covers.
Pros
Cons
Best for: A 2-stroke saw or strimmer whose removed plug matches this cross, after you check thread and resistor on the plug in your hand.
Less suitable: Anyone who needs a stated resistor, a stated 14 mm reach, or a single Champion code such as RCJ7Y with no ambiguity.
Specifications
Common questions
What thread size is in the specification cell?
The thread cell says M10. The bullets still list BPMR7A among the crosses.
Does the listing say the plug has a resistor?
The cells do not say. One UK review says these plugs have no resistor, and that a listing cannot be both the R and the non-R code.
What did UK reviews fit it to?
Strimmers, a Stihl FS55, chainsaws and at least one lawnmower. One review says it did not cure a chainsaw that already ran badly.
Two F7RTC plugs at £5.79. The listing line is 4.5 from 11 reviews, which is a small sample, and the only UK review text in the file is the word Super. No reach, gap or engine model is printed, so you cannot check the plug against a Briggs or Honda row from this page alone. The thread cell says #14, and the core cell says iridium. The rank cell is 134 in Car Spark Plugs, and the title also mentions a toolbox and a cabinet. Treat the lawnmower words as a claim. Buy it only if the plug already in the engine reads F7RTC and you can match the thread yourself.
Pros
Cons
Best for: Only if the plug already in the engine reads F7RTC and you can match the thread yourself.
Less suitable: A buyer choosing from a mower model number. This file does not give one.
Specifications
Common questions
Which engines are named?
None. The bullets say lawn mowers, motorcycles and cars. The thread cell says #14. Reach, hex and gap are not stated.
How is it rated?
The listing line is 4.5 out of 5 from 11 reviews. The only UK review body in the file is the word Super.
Is the fit certain?
No. The title includes lawnmower and also toolbox and cabinet. The rank cell is car spark plugs, not lawn mower spark plugs.
Three RJ19LM plugs at £4.89, 4.3 from 153 reviews, with Classic, Sprint, Quattro and Quantum names in the bullets. UK reviews include a lawnmower and a JCB rotavator that ran after the change. The same file describes a hex that would not take a 13/16 socket, the size many Champion flathead plugs use. One Macallister stopped because the plugs overheated, which is a limit on treating the title as a heat-range match rather than a lab result. You still read the code on the old plug before you rely on those Briggs family names. An overhead-valve engine that calls for RC12YC is outside this listing.
Pros
Cons
Best for: A flathead mower whose old plug reads RJ19LM, if you have a socket that fits the smaller hex described in reviews.
Less suitable: An OHV engine, or a buyer who only owns a 13/16 socket and expects the Champion hex.
Specifications
Common questions
Which engines does the listing name?
The bullets say Classic, Sprint, Quattro and Quantum. A Quantum code date is not in the file.
Will it fit a 13/16 socket?
The file has no hex measurement. Two UK reviews say the nut is smaller than a Champion equivalent and that a 13/16 socket does not fit.
What running fault appears in UK reviews?
One reviewer says the plugs overheated quickly in a Macallister with a Briggs & Stratton engine and the engine stopped.
Six short-reach crosses at £8.89, 4.3 from 18 reviews, with a 14 mm by 9.5 mm thread cell and Stihl and Husqvarna model names in the bullets. That reach matches the short two-stroke pattern, so a six-pack only makes sense when several tools already use this L7T or BPMR7A code. The UK reviews in the file are short and positive, and none describes a failure, though 18 reviews is a thin sample next to the NGK single in this set. The warranty cell says no. A four-stroke walk-behind that calls for RJ19LM or RC12YC is outside what these bullets describe. You still set the gap from the tool manual after delivery.
Pros
Cons
Best for: Several 2-stroke tools that already use this L7T or BPMR7A code, so a six-pack is actually shared.
Less suitable: A single four-stroke mower, or anyone who needs a warranty cell that says more than no.
Specifications
Common questions
How many plugs, and what thread?
Six plugs. The thread cell says 14 mm x 9.5 mm. The bullets say fixed tail caps.
Which machines are named?
Stihl MS170 and MS180 among others, Husqvarna 61 to 272XP, plus lawnmowers, strimmers, blowers and small petrol engines. The listing says check the model.
What do the UK reviews say?
Five short UK reviews call them good value and say they did the job. None describes a fault. One reviewer had used only one of the six.
Two L7T plugs at £5.99, 4.1 from 9 reviews, with about 13.7 mm thread diameter and about 52 mm overall length in the bullets. Two UK reviews say they did the job. One says three electrodes made gapping hard, and one says both plugs failed. Nine reviews is too small to treat either outcome as typical. There is no printed gap, so you still set the figure from the engine manual after the plugs arrive. A BR2LM flathead plug is a different code, and this listing does not show that you can swap the two on reach alone.
Pros
Cons
Best for: A lawnmower whose removed plug is marked L7T, if you can gap a three-electrode plug as that review describes.
Less suitable: Anyone who needs a single-electrode plug with a printed gap, or a BR2LM flathead plug without checking the reach.
Specifications
Common questions
What should you check before fitting?
The bullets say compare the L7T mark, thread, reach, hex, terminal, electrode layout and gap with the plug you removed and with the engine manual.
What did a UK reviewer say about the electrodes?
One review says there are three electrodes, which made the gap difficult, and that the plugs were then fitted to a lawnmower.
Did any review say the plugs failed?
Yes. One UK review says both plugs are not working.
Two XC92YC plugs at £3.99. The listing line is 4.0 from 2 reviews, and there is no review text to show which machine was fitted. The bullets name Z335, Z345 and Z355 strings and MIU11020, and they mention a twin, which is the practical reason to buy a pair of the same code. The warranty cell says no. With two reviews and no fitting story, you are buying the code printed in the bullets, not a measured mower result. A walk-behind flathead or a two-stroke saw is not named on this listing. Check the parts list for XC92YC or MIU11020 before you rely on the model strings.
Pros
Cons
Best for: A machine whose plug or parts list says XC92YC or MIU11020, including a twin that needs two of the same code.
Less suitable: A walk-behind flathead or a two-stroke saw. Those codes are not on this listing.
Specifications
Common questions
Which model strings are on the listing?
Z335E, Z335M, Z345M, Z345R, Z355E and Z355R, plus MIU11020. The title also prints Z355. Thread and gap are not stated.
How many reviews is the score based on?
The listing line is 4.0 out of 5 from 2 reviews. The file has no review text, so there is no theme to quote.
Does the listing mention two plugs in one engine?
Yes. The bullets say the pair can replace both plugs in a dual-cylinder machine.
Two plugs at £4.99 with no customer-reviews line, so there is no star score to weigh against the other rows. The title describes a 14 mm by 1.25 mm lawnmower plug. The included line says L7T, while the bullets name Classic, Sprint, Quattro and Quantum, which are flathead family names rather than a short-reach two-stroke code. Do not treat those strings as one fit. The rank is 332 in Lawn Mower Spark Plugs, which only places the listing in that list. Read the code on the plugs that arrive and match it to the engine before you fit them.
Pros
Cons
Best for: Only after you read the code on the plugs that arrive and match it to the engine. The file does not settle which code that is.
Less suitable: A buyer who needs either a proven L7T or a proven RJ19LM and cannot inspect the marking first.
Specifications
Common questions
Which code is in the box, according to the file?
The included-components line says two L7T plugs. The bullets instead name Classic, Sprint, Quattro, Quantum and older opposed twins. Those are not the same claim.
Is there a star rating?
No customer-reviews line and no review text.
What thread does the title state?
14 mm x 1.25 mm. Reach and gap are not stated. The bullets say no special tools.
One BPMR7A-marked plug at £5.39 from OmniCraft, with the manufacturer cell naming XuanQiMY. There is no customer-reviews line, so there is no star score and the comparison score stays at 0. The bullets limit it to 2-stroke kit in the 47 cc to 50 cc range, name Stihl MS170-series and Husqvarna chainsaws, and tell you to verify the part number. Thread and gap are not printed, though the core and top cells both say copper. At £5.39 it costs more than the NGK BPMR7A single in this set without adding a review sample. It is a possible match only when your manual already says BPMR7A for a tool in that capacity band.
Pros
Cons
Best for: A 47 cc to 50 cc 2-stroke whose manual says BPMR7A, if you accept a listing with no reviews.
Less suitable: A four-stroke mower, or a buyer who wants a star line before paying £5.39.
Specifications
Common questions
Is there an amazon.co.uk star line?
No. The amazon.co.uk capture has no customer-reviews line and no review text.
What does the title say it fits?
A 2-stroke lawnmower, chainsaw and brush cutter. The bullets add Stihl MS170-series and Husqvarna chainsaws, and 47 cc to 50 cc engines, and tell you to check the part number.
What material cells are filled?
Core and top both say copper. The bullets also say an alumina silicate ceramic insulator and a copper core.
Scores on this page are the figures already stored for each amazon.co.uk listing on 22 October 2026. Each score is the star rating multiplied by 20, so 4.8 becomes 96. If the customer-review count is under 100, that stored score subtracts 8. If the amazon.co.uk capture has no customer-reviews line, the score is 0. Shelf price does not create a score. It is used only afterwards, to choose the best value among plugs that already have a score. The top pick is the highest score. Plug code, thread, pack and gap stay in the table and are not turned into points. Twelve listings stayed in. This is not a laboratory test.
Amazon.co.uk listing score
100%The stored score is the amazon.co.uk star rating multiplied by 20. A 4.8 line starts at 96. If the customer-review count is under 100, the score subtracts 8. At 100 reviews or more there is no deduction. If the amazon.co.uk capture has no customer-reviews line, the score is 0. Plug code, thread, pack, gap and hex stay in the comparison cells, including cells that disagree, and they are not turned into points. Shelf price is recorded as shown and does not create a score. The top pick is the highest of those stored scores. The best value is chosen after the scores, among plugs that already have a score, and it is not automatically the lowest price.
Match the code, the reach and the gap to the engine. A 14 mm thread is not a fitment, and a title that says lawnmower is not a type.
A lawnmower spark plug is the replaceable ignition part in a small petrol engine. You usually buy one when a walk-behind mower, a ride-on, or a related garden engine is hard to start. The code on the old plug, or the code in the engine manual, is the purchase. The word lawnmower in a title is not a fitment. Thread diameter, thread reach, hex size, heat range, resistor and electrode gap have to match that engine together.
Flathead, overhead-valve and short-reach two-stroke plugs are different families. A 14 mm thread can screw in and still run hot, foul, or fail to seat. Read the code on the plug you removed.
Many walk-behind rows are 0.76 mm. Some dated rows are 0.51 mm. A short-reach two-stroke chart often states 0.7 mm. Check the gap after delivery, because a loose parcel can move it.
The letter R means a resistor. One UK review said a resistor plug was a poor swap for a non-resistor plug on a hand-pull chainsaw. Neighbouring heat-range numbers are not substitutes either.
The engine model and type come first. On some small engines a code date changes the part and the gap, so a family name such as Classic, Sprint, Quattro or Quantum is not a single plug. Flathead walk-behind codes and overhead-valve codes do not interchange. Short-reach two-stroke plugs for saws and strimmers are a third family. A 14 mm thread is the start of the check, not the end. Reach and hex decide whether the plug seats and whether your socket fits.
Heat range is the number in the code, and the next number is not a substitute. One UK review of a Mountfield engine said it needed the next heat range, not the plug that had been ordered. The letter R means a resistor. One UK review said a resistor plug was a poor swap for a non-resistor plug on a hand-pull chainsaw. If the listing cells do not state a resistor and a review says there is none, while the cross list mixes R and non-R codes, treat that row as unresolved.
Three typical situations, each with a recommendation from this comparison.
Read the code off the old plug before you buy. If that code is RC12YC, the Briggs & Stratton pair is the top pick at about £7.99. The stored score is 96, from 4.8 and 2,482 amazon.co.uk reviews. The Number of Items cell says 1 while the title says two, so count what arrives. A flathead code such as RJ19LM is a different row, and an overhead-cam engine is outside this listing.
Do not buy a four-stroke mower plug because both titles say garden. If the tool already says BPMR7A, the NGK single is the best value at about £3.91. The score is 94, from 4.7 and 5,929 reviews, the largest count in this set. The gap cell prints 9.5 mm and does not say whether that is the electrode gap or the reach. One UK review said the resistor was a poor swap for a non-resistor CJ8 on a hand-pull saw.
Buy the engine maker’s number and keep the service interval. Briggs & Stratton UK says check or replace the plug every 25 hours or once a season, and not to tighten past 15 ft lb on that page. For an overhead-valve engine whose parts list says RC12YC, the pair at about £7.99 is that maker’s code in this set. It is not a plug for every machine on the yard, and a two-stroke saw still needs its own code.
The top pick is the Briggs & Stratton RC12YC pair at about £7.99. The stored score is 96, from 4.8 and 2,482 amazon.co.uk reviews. The title says an RC12YC pair, and the Number of Items cell says 1, so count what arrives. One UK review says the terminal was too large for a new coil boot. The best value is the NGK BPMR7A at about £3.91. The score is 94, from 4.7 and 5,929 reviews, the largest count in this set. It is not the lowest price. The NGK BPR5ES is about £3.54 with a score of 92 and does not take the value badge. The BPMR7A gap cell prints 9.5 mm and does not say whether that is the gap or the reach. An OMCGG F6RTC pair also scores 94, from 4.7 and 109 reviews, and does not take a badge. Neither result is a laboratory test.
Briggs & Stratton RC12YC pair
Score 96 from 4.8 and 2,482 reviews at about £7.99, an RC12YC pair whose pack-count cells disagree.
NGK BPMR7A
Score 94 from 4.7 and 5,929 reviews at about £3.91, not the lowest price in the set.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Buying notes from the sources below, checked for this page on 22 October 2026. Prices, stars and review counts are from the amazon.co.uk captures of that date. Two listings had no customer-reviews line.
This page contains affiliate links to amazon.co.uk. If you buy through them, we may earn a commission at no extra cost to you. The scores follow the listing rules above. They are not a lab test, and they do not promise the cheapest price.
