Thomas the Tank Engine Wikia
This article is about the diesel engine. You may be looking for Diesel 10, the Story Library book, or the Engine Adventures book.

“Your worthy Sir Topham Hatt thinks I need to learn. He is mistaken. We diesels don't need to learn. We know everything. We come to a yard and improve it. We are revolutionary.”

"Devious" Diesel, as his name implies, is a black diesel engine who originates from British Railways, and is the first known standard-gauge diesel to ever arrive on Sodor. In Thomas & Friends, Diesel eventually becomes a permanent resident of Sodor.


The Railway Series

When Diesel visited the North Western Region on trial from British Railways, Duck was asked to show him around. Duck was unimpressed by Diesel's claims of being "Revolutionary" and left him to his own devices. As a result, Diesel was made into a laughing stock by the trucks for trying to pull some rusty old trucks and failing spectacularly.[4] Diesel then blamed Duck for not helping him and swore a vendetta plan; he spread rumours that Duck had given the big engines rude nicknames, which led to Duck being sent to Wellsworth pending an inquiry into the matter.[5] Diesel meanwhile got too big for his buffers and started telling lies about Henry, but he was found out and sent home in disgrace.[6] His visit was brief but impactful, as his behaviour left a bad impression about diesels to the Sodor engines.

Several years later, Diesel was brought back to help on Thomas' Branch Line whilst Percy was being repaired. Diesel tried to win Thomas and Toby over, without success and after he destroyed an old truck, he was to be sent away. However, on his day of departure, Clarabel slipped on oily rails left by Daisy and came off at some points near Dryaw. Diesel - realising that Thomas was blocking his only way home - went to the rescue. Clarabel put in a good word for him, and Diesel - although he returned to the Other Railway - has since always been welcome on Sodor.[7]

Thomas & Friends

Diesel's first visit to Sodor was directly adapted from The Railway Series and happened virtually the same way. Following occasions where Diesel was seen in the background are when he attended the Christmas party at Tidmouth, the celebration of City of Truro's visit and shunted trucks in Knapford Yards.

Years after their first encounter, he returned when Duck and Percy needed help at Brendam Docks. Since Diesel was the only engine available, Sir Topham Hatt was forced to give him a second chance, much to Duck's dismay. Duck and Percy refused to work with Diesel and stayed in the shed, leaving Diesel to work by himself and causing the work to pile up, which made Sir Topham Hatt intervene and send them back to work. Things did not improve, and Diesel bumped into Percy after his driver failed to put Diesel's brakes on properly. He then roughly shoved some trucks, spilling the loads everywhere; Duck and Percy remained quiet out of fear of being telltales. This convinced Diesel that he could be as bad as ever and shunted some trucks of china clay right into the sea. After this, Sir Topham Hatt sent Diesel away (with the intent of his expulsion to be permanent), but Diesel somehow mysteriously returned to give Mavis advice and taunt Gordon about the triumph of diesel power on the Mainland. It is possible that these events happened during Diesel's stay or he was delivering goods from the Mainland.

When Henry was derailed by some trucks, Diesel was brought back as a last resort to do his goods work. Unfortunately, his attempt to have Sir Topham Hatt replace steam engines with diesels backfired when he tried to prove that he was the world's strongest engine which resulted in him falling into a barge and he was sent back to the Mainland yet again.

Later on, Diesel returned yet again, this time to assist Fergus at the Sodor Cement Works. Diesel became jealous of Fergus' reputation as the "pride of the Cement Works" and got cross because of Fergus' deep regard for the rules and always telling him "Do it right", especially while carelessly bumping some trucks out of the hopper. He then concocted a scheme to make Fergus run away. Diesel was partially successful (he managed to make Fergus abandon his post for a time), but was ultimately foiled. Amazingly, Diesel was not sent back this time around, as Sir Topham Hatt told Thomas and Fergus he would move Diesel to the smelters (possibly because he might have not seen any point in bringing Diesel in as a spare engine and then sending him back for his bad behaviour); Diesel has remained on the North Western Railway since.

Despite remaining tricky and devious, Diesel learned how useful steam engines can be when Thomas brought fresh diesel fuel for him and the other diesel engines and James pushed him back to the Repair Yard when he broke down. However, he tried to convince Gordon that he was old and clapped out, Ben that there was a monster inside a tunnel and Thomas about the "Curse of the Cliffs" and scared him at Halloween.

But Diesel proved to have a good side inside him when he told Emily about his record he made for shunting lots of trucks in one day than any other diesels and proved to Thomas that he did not ruin the photograph for the billboard on purpose.

Although there's good in him, Diesel likes to be competitive and he once challenged Thomas to race backwards at the Quarry. Thomas accepted to race Diesel, but soon they caused problems at the Quarry.

Although Diesel made fun of James when he was painted pink, he tried his best to prove himself to be as useful as the steam engines when he took all of the Jobi wood to the Sodor Search and Rescue Centre - only to put himself in danger requiring Thomas to rescue him. [8] However, Diesel tried again to prove how special he is when he took Thomas and Rosie's loads to market and stole James' pigs so that the children could see them. But it was only when Diesel brought the load of slate for the school that he proved himself Really Useful.

Diesel was also one of the diesels that took over the Sodor Steamworks. [9] He later teased Flynn for just standing around and doing nothing.

Paxton told Diesel about Luke and Diesel tried to get Luke sent away from Sodor, but he failed when he was scolded by the Fat Controller. [10]

When he and Percy collected a calliope, he thought Percy would not be able to make it play but was surprised when he did.

In the seventeenth series, Diesel was one of the diesels that brought the Christmas decorations to Tidmouth Sheds. Later, he was biffing trucks around even when Edward told him to stop. Diesel spilled the milk in the trucks and when the Fat Controller opened the truck doors, the milk splashed all over his trousers. When Hiro told Diesel, he told Hiro to toughen up with the trucks. But when Hiro would not listen, Diesel coupled himself up on the back of Hiro's train and helped the trucks play tricks on him. To make the trucks stop, Hiro braked suddenly before the platform, causing three barrels of cream to splash all over Hiro, Edward and the Fat Controller. Diesel tried to get away but was blocked off by Thomas. As punishment, Diesel had to learn the proper way of handling trucks by Hiro.

In the eighteenth series, Diesel - along with Norman, Sidney, Den and Dart - hid from Paxton at the Dieselworks, which resulted in Paxton going on a wild goose chase to find all of the diesels and ended with Diesel running out of fuel. This led to Paxton helping him to the next station to refuel. Later, he argued with Thomas over who should be the back engine for a train of trucks heading from Ffarquhar Quarry to Brendam Docks. He later tried to delay Mavis returning to the quarry, which led to Thomas taking the train by himself and resulted in him having an accident. Diesel even tried to blame Mavis for it, but Sir Topham Hatt was wise to his tricks and he let Thomas work with her instead. He later joined the engines at Knapford during the Christmas Holidays and agreed with the Fat Controller that the last train would possibly be cancelled. He also teased Samson about how the tank engine got lost when he first came to Sodor.

In the nineteenth series, Diesel covered Paxton in a cloud of black smoke from his engine and left Paxton's face covered in black spots.

At Christmas time, Diesel was being very unhelpful with the extra work, so Thomas, Emily, Salty and Paxton made a plan. On the night before Christmas morning, they pretended to be ghosts to scare Diesel, scaring him to the point where he flew off the tracks and derailed. After he was recovered the next day, he learned the true meaning of Christmas. On Christmas morning, Diesel was feeling very merry and he brought the Fat Controller to the Earl's Christmas lunch at Ulfstead Castle.

He later tricked Percy into going to an old quarry so that he could do Percy's job of picking up the Mayor to take him to a ceremony. Diesel later found Percy stuck in a flood with his fire out. He tried to rescue the tank engine but only made the situation worse when the water damaged his generator and he got stuck too. After the two were rescued by the Search and Rescue team, Diesel was sent to have his engine repaired.

In the twentieth series, Diesel was shown to care for some ducklings that he thought were cute. Later, Annie and Clarabel played a trick on Daisy while Thomas was on quarry duty. This led to Diesel being sent to pull them instead, much to their dismay though Diesel was polite to them despite bumping them.

Diesel wanted to go to the Great Railway Show. When the Fat Controller was hesitant in bringing him, Diesel tried to prove himself by having crates put over Den, Dart and Paxton so that they would resemble trucks and put them in a long train. When the Fat Controller was in the final stages of choosing who would go to the show, Diesel planned to demonstrate how strong he was by pulling the train, while in reality, Den, Dart and Paxton were doing most of the work. His unusual train however was blocking any way into Knapford Yard, so Thomas coupled up to the train both so that he could get into the station and so that he could prove himself worthy to go to the show. The diesels heard Thomas' whistle and thought it was Diesel's horn, so they began pushing, much to Diesel's horror. Thomas then collided with Norman at a set of points and lost his left buffer as a result. Diesel later got stuck inside one of the crates and was accidentally loaded onto a ship by Cranky. [11] He somehow managed to return to Sodor before the events of the twenty-first series.

In the twenty-first series, he damaged Daisy's springs and caused mischief between her and Harvey by telling them both that the other was boasting about being unique, which led him falling into the sea after his plan failed. He later brought the coal delivery to the steam engines during a big freeze.

In the twenty-second series, he, Bill and Ben laughed at Thomas and Rosie because of their friendship at Brendam Docks after the devious diesel bumped into the red engine while Cranky was unloading a crate of roses during Valentine's Day.

In the twenty-third series, he continued to cause more confusion and delay than before by sending Rebecca to do the other diesels' jobs improperly as a trick to pay them back as they do not get into trouble as he does. Unfortunately, he was cornered at the Dieselworks and Rebecca's honest nature meant that she was quick to tell Sir Topham Hatt about her favour for Diesel. The Fat Controller was very cross with him after hearing what had happened that day, with Diesel left to be upset about being in trouble again. He also wanted some engines who thought he was not reliable at all - particularly Paxton and Nia - to come and find him hidden with some glow-in-the-dark paint at the Blue Mountain Quarry, to which they told him off for not doing his jobs for two whole days due to his self-interested and sinister attitude.

In the twenty-fourth series, when Sonny was having his second chance upon arriving on Sodor and not being trusted because of his previous status quo of a thief, Diesel took advantage of this; he used Sonny by pretending to be his "friend" and do his jobs for him due to Sonny wanting to be really useful and stay there. But following an argument with Percy at Ffarquhar, the tank engine found out his plans and got upset with him which led to Diesel derailing at a dig site. But luckily, he was rescued by Sonny who ended up changing his mind. This however led to Sonny accidentally derailing his trucks to which Sir Topham Hatt was going to send him away, but Diesel ended up feeling guilty, admitted that all the chaos was his fault and the tank engine was officially accepted on the railway.


Diesel is, in essence, the average pantomime villain. He is oily, malicious, devious, scheming and full of ideas to get revenge. He views himself and any other diesel as highly above the steam engines and believes that all diesels are "revolutionary" - he has also claimed diesels should be "rough and tough", as an excuse for bullying the other engines. His antics give diesels on Sodor a bad reputation, which causes most steam engines (particularly Duck and Thomas) to distrust him. His rough demeanour also affects his fellow diesels, who are often victims of his tricks alongside steam engines, mainly diesels who are friendlier to steam engines and are just nice in general, with Paxton and Sidney being prime examples. As such, Diesel has very few friends, mostly associating with diesels whose personalities align with his, such as Diesel 10 or ‘Arry and Bert. He also enjoys using gullible engines (such as Paxton and Rebecca) as pawns in his plans.

However, despite his antics, Diesel still wants to prove himself to be a Really Useful Engine. He is also very proud to be the first diesel on Sodor and seems to have a soft spot for cute ducklings, which he is embarrassed by because he believes it ruins his tough exterior. Diesel will also more often than not focus more on his own work than help anyone else, but he will help any engines, steam or diesel, when it comes down to it. Due to the amount of chaos his web of lies set off on his first day on Sodor, Diesel has often been seen as a liar by the other engines, leaving them to blow off his news as bluffs until absolutely proven. This is not helped by the fact that he lies whenever he gets the chance, further reinforcing their beliefs.

Lately, Diesel is portrayed as a typical bully with a lack of forethought. While sinisterly cunning, he usually neglects to think of what would happen if things were found out and due to the transparency of some of his plans, he always gets his comeuppance in the end. His distaste for steam engines has also been dropped (most likely due to the show targeting a younger audience), being replaced by a mean-spirited prankster nature and inflated arrogance. He also shows several hints of manipulative and self-serving tones, as he can be found as very lazy. Proving this, he managed to trick Sonny into doing his jobs for him, though much like Daisy and Dennis (both of whom who have tried similar tactics), Diesel was immediately struck by karma, having his luck deteriorate due to his selfishness. He also made fun of James when he was painted pink and Thomas when he was dressed up as a monkey, finding both to be humorous contrary to how they actually felt. Diesel does know when he goes too far, however, and usually owns up for his misdeeds if the situation demands it. This has allowed him to form genuine lasting friendships with such engines as Daisy and Harvey.

Despite his devious and malicious nature, Diesel is shown to be nice and caring towards children, (a side that is never present when it comes to other engines) even feeling guilty for making them upset when he did not bring the roof tiles for the school roof and owning up for his mistakes which made them happy when he finally brought the tiles.

Technical Details


Diesel is based on a British Rail (BR) Class 08 diesel-electric shunter. In the real world, BR Class 08s were in fact the most successful shunting engines in the world with 996 of them built. Over seventy of them are preserved by heritage railways, such as the Dean Forest Railway and museums, such as the National Railway Museum. Around one-hundred BR Class 08s also remain in service on the national rail network. 08850, a BR Class 08 preserved by the North Yorkshire Moors Railway, appears in a Mr. Perkins' Railway segment.

'Arry, Bert, Splatter, Dodge, Paxton, Sidney, Ulli, the Mainland Diesels and Fernando are also based on BR Class 08s along with the international Brazilian, Indian and Chinese diesels. Two BR Class 08s also appear in The Railway Series.


Diesel is painted in the BR mixed-traffic black livery, which was the standard livery for shunting engines from 1948 until the mid-1960s. His side rods were painted silver until the sixth series, where they were painted black.


Thomas & Friends


He was also likely to appear in the WWII film.

Music Videos

Learning Segments


Magazine Stories

Diesel also appeared in the magazine stories, A Special Story about Steam, Blowing About!, Clean Getaway!, Diesel Display, Diesel's Nasty Turn, Diesel Causes Delay, Fishy Diesel!, Making a Mess!, Mountains and Mess!, Nice Neville, Percy and the Trucks, Ride and Slide, Road Ride, Rocking About, Slick Trick!, Sodor's Strongest Engine, Special Places, The Christmas Sacks and The Runaway Percy

Annual Stories

Audio Stories

Official Description

From Official Website:[1]

Diesel: Devious Diesel, the other engines call him behind his back and sometimes, (when he's been more than usually obnoxious) to his face. Oily, scheming and ever ready to stir up trouble in the shed, his characteristic smirk is a sure sign that somebody, somewhere, is in for a bit of trouble.

Historical Note: Diesel's likeness is that of an ordinary 0-6-0 Diesel Electric British Rail Shunting Engine.

From Official Website:[2]

Diesel: "Devious Diesel" , as he is referred to by the other engines, is always bad news when he's around. Oily, scheming and ever ready to stir up trouble in the shed, his characteristic smirk is a sure sign that someone, somewhere is in for a bit of trouble.

Fun Fact: After telling false stories about Henry, Diesel was sent away by Sir Topham Hatt.

From Official Website:[3]

Diesel: Diesel believes that Steamies are no match for Diesels. Oily, scheming and ever ready to stir up trouble in the shed, Diesel's characteristic smirk is a sure sign that some Steamie, somewhere is in for a bit of trouble. However, given a chance, Diesel wants to show that he's a Really Useful Engine too!

Fun Fact: Diesel has shunted more freight cars in one day than any other diesel. He is based on a British Rail Class 08 Diesel-Electric Shunter.


Audio Files



First used Last used Sound Effect
Series 2 Thomas & Friends: Adventures!

From his merchandise, Misty Island Rescue, the fourteenth series and some games, Diesel is portrayed with a different horn that would later be reused for Mavis in the fifteenth series onwards.

First used Last used Sound Effect
Take-n-Play Go Go Thomas! (2018 version)

In the Arc Productions era, Diesel was given a new horn that is a two-toned version of the previous one. Both of his horn's notes are the same, unlike Rusty and Dart, since both of their two-toned horns have two different notes.

First used Last used Sound Effect
Series 17 Series 24

In one scene of Calling All Engines!, Diesel is incorrectly portrayed with 'Arry's horn from the same special.

First used Last used Sound Effect
Calling All Engines! Calling All Engines!

In Fun Cubes, Diesel is incorrectly portrayed with Derek's/Salty's current horn sound.

First used Last used Sound Effect
Fun Cubes Fun Cubes

In one episode of Learning with Thomas, Diesel is incorrectly portrayed with BoCo's S2-5 Horn.

First used Last used Sound Effect
Learning with Thomas Learning with Thomas

In the early version of the Guess Who? Puzzles segment, Diesel is incorrectly portrayed with Diesel 10's horn.

First used Last used Sound Effect
Guess Who? Puzzles Guess Who? Puzzles


  • Diesel was the first diesel engine to be introduced in both The Railway Series and the television series.
    • He was created when Eric Marriott, the editor of The Railway Series at the time, suggested that Awdry should introduce a diesel in order to keep the books up to date.
  • In some merchandise lines, Diesel is referred to as "Devious Diesel". It was not until the seventh series episode, Fergus Breaks the Rules that he was referred to by this name on-screen.
  • Between the thirteenth and sixteenth series, Diesel was the only character from the model series to still be voiced by the narrator in the CGI Series. However, this was only in the US narration.
  • As revealed in the tenth series episode, Emily and the Special Coaches, Diesel is a record holder for most trucks shunted in a single day.
  • Diesel has travelled at well over his top speed of 20 miles per hour on numerous occasions in the television series.
  • Throughout voicing Diesel:
    • In the UK narration of the thirteenth series onwards and the US narration of the nineteenth series onwards, Kerry Shale gives Diesel a faint hoarse Cockney accent.
    • In the US narration, Michael Brandon gave him a gruff American accent and Martin Sherman gave him a gruff New Jersey accent.
    • In the Learning with Thomas segments, Rob Rackstraw gave Diesel a voice that sounds similar to Spud the Scarecrow from Bob the Builder, a series Rackstraw has voiced in.
  • Up until Series 13, Diesel was female in the Greek dub.
  • Diesel's face in the magazine stories is often smaller than in the television series.
  • According to the magazines and the DVD Bingo game, it reveals that Diesel and Bulgy are good friends.
  • Nathan Clarke did an audio sample for Diesel on his DAA Management Page. [12]
  • Diesel's television series model is now owned by the Explore the Rails exhibition, previously on display at the British Museum during the 70th anniversary.
  • Diesel had a total of sixteen facial expressions, one of which a weary face was never shown on-screen.
  • The fifth series is the only series that Diesel does not appear in after his introduction in the second series.
  • Diesel is Ringo Starr's favourite character [13].
  • Diesel's normal horn sound was mistakenly reused for Salty in the eighth series episode, Percy's New Whistle and on the Diesel's Locomotion Mayhem ride at Drayton Manor Theme Park. It was also mistakenly reused for Mavis in the game Engines Working Together and on the Diesel's Locomotion Mayhem ride at Drayton Manor Theme Park, however her horn sound from Calling All Engines! can be heard when Every Cloud has a Silver Lining still plays there. It was also mistakenly reused for Bert on the Diesel's Locomotion Mayhem ride at Drayton Manor Theme Park, same with Dennis and Rusty. It was mistakenly reused for Paxton, but only in the fifteenth series episode Fiery Flynn. It was also mistakenly reused for Diesel 10 in Little Engines Easy Reading: Day of the Diesels in the mobile app, Read and Play!.
  • Diesel's horn sound used in some of his merchandise, Misty Island Rescue up to the fourteenth series and some games was reused for Mavis in the fifteenth series onwards (excluding the sixteenth series episode Thomas and the Sounds of Sodor). It was also reused for one of The American Diesels. It is actually a generic train horn stock sound effect and is used in many other pieces of media, such as Chuggington.



* RWS only | ** T&F only

* RWS only | ** T&F only | --- Dropped