"Devious" Diesel is a troublesome diesel shunter who came from the Other Railway on trial for the North Western Railway, and was the first diesel engine to come to Sodor. Although he has been sent away in disgrace several times, he still manages to come back to stir up more trouble.
Diesel arrived on the Island of Sodor on June 1957 as an engine on trial to the North Western Railway. Upon his arrival, Duck was asked to show him around the yard at Tidmouth, but Diesel insisted that he already knew what to do and boasted of his superiority. Unimpressed, Duck left Diesel to collect his trucks by himself while he fetched the coaches for the express. Delighted to show off, Diesel collected a train of old trucks from a siding and attempted to move them, but failed when their brakes came on and the coupling snapped. As a result, Diesel became a laughing stock among the trucks, and the incident made him despise Duck, blaming him for not helping him.
Determined to have Duck sent away, Diesel began spreading lies about him to the trucks, claiming that Duck was insulting the bigger engines behind their backs. As a result, the bigger engines turned against Duck, and he was sent to Wellsworth while the Fat Controller investigated the situation, but Diesel got too big for his buffers and began spreading lies about Henry. Diesel was caught in his lies, and he was sent back to the Other Railway in disgrace. (RWS; Duck and the Diesel Engine)
Years later, Diesel returned to the North Western Railway to help out on the Ffarquhar Branch Line when Percy was feeling ill, as he was the only engine available for the job. However, Diesel caused even more trouble during his second visit, destroying a row of old trucks when he smashed them through a set of buffers and a fence. On his last day on the Island, Diesel managed to redeem himself when he helped Thomas pull Clarabel back onto the rails when she had derailed at some trap points. Diesel left a positive impression on the Ffarquhar Branch Line engines, and after he left the Island and returned to the Mainland, they wished for him to return. (RWS; Thomas and the Evil Diesel)
Diesel returned to the North Western Railway sometime after his departure to help Duck and Percy when the work at Knapford Harbour was becoming too much for either of them to handle. Percy and Duck were not impressed upon finding out Diesel had returned, and both went on strike until the Fat Controller confronted them, leaving Diesel to do most of the work by himself. Believing he could get away with his bad behaviour, Diesel shunted some trucks of china clay on the key, but smashed them through a set of old buffers and into the sea. This was the final straw for the Fat Controller, who sent Diesel away immediately. (TVS; Diesel Does it Again)
Even though he was sent away, Diesel mysteriously returned to Sodor under unknown circumstances. When Mavis began complaining about Toby, Diesel told her that diesels were better than steam engines at anything, even though he knew nothing about shunting. (TVS; Mavis) He was also present when the Flying Scotsman was at Knapford Harbour (TVS; Tender Engines), and was at Tidmouth Sheds when City of Truro was visiting the railway. (TVS; Gordon and the Famous Visitor)
After Henry had an accident which damaged him, Diesel was sent back to Sodor to fill in for him, as he was the only engine available. During his stay, Diesel was determined to prove that he was stronger than Henry and attempted to pull as many trucks as possible, arranging at least twenty of them. However, the trucks' brakes were put on, and when the coupling snapped, Diesel shot forward and rolled off the dock, falling into a barge. Diesel was sent to the Mainland in disgrace when Henry returned from the Works. (TVS; The World's Strongest Engine)
Diesel later returned to the Island to help Fergus at the Cement Works. However, Diesel was still up to no good and insisted that the Fat Controller wanted Fergus to work at the Scrapyards, managing to fool Fergus into leaving the Cement Works. When the Fat Controller found out about this, Diesel was transferred to the Scrapyards to work there. (TVS; Fergus Breaks the Rules)
When Percy was having a fallout with Thomas, Diesel 10 ordered Diesel to manipulate Percy into coming to the Vicarstown Dieselworks, which Diesel succeeded at doing. Once when Percy had supposedly befriended the diesel engines, he led them to the Sodor Steamworks, where Diesel 10 betrayed him and took it over, allowing Diesel and the other diesel engines to run around freely within the workshop. The Fat Controller arrived at the Steamworks, and after being told about the Dieselworks, he agreed to have it restored. Diesel helped the steam and diesel engines to restore the Dieselworks to its former glory. (TVS; Day of the Diesels)
Diesel became especially troublesome during the Christmas season, and refused to help any of the engines when they needed assistance. After refusing to help several of the engines, Thomas planned to get back at him. To do this, he had Emily, Salty and Paxton pretend to be ghostly engines in an attempt to scare Diesel into behaving better. After his encounter with Paxton, Diesel became so scared that he ran away, but ran over a piece of damaged track and derailed.
Once when Diesel had derailed, Thomas pretended to be a ghost himself and scared Diesel into believing that he would remain derailed for the rest of his life if he did not behave better. Diesel became so frightened that he immediately changed his ways, and became much friendlier and helpful towards the engines for the rest of the day, even participating in the Earl's Christmas luncheon at Ulfstead Castle. (TVS; Diesel's Ghostly Christmas)
When Diesel found some ducklings near the railway line, Thomas found him adoring them as he was doing his work. Thomas agreed not to tell the other engines about Diesel being a softie in exchange for Diesel's politeness. Diesel agreed, and began acting uncharacteristically kind to the steam engines, but struggled to maintain his nice demeanor and began acting troublesome again to impress 'Arry and Bert. Thomas finally told 'Arry and Bert about the ducklings and took them to the duck pond to see them, much to Diesel's horror. Diesel believed that the Ironworks twins would tease him, but much to his surprise, they adored the ducklings just as much as he did. (TVS; Diesel and the Ducklings)
Upon hearing that Henry would be in the Great Railway Show, Diesel decided to prove that he was stronger than him once again to convince the Fat Controller that he would be a better engine for the strength competition. To do this, he had Den, Dart and Paxton disguised under large crates and added them to a train of trucks, making it appear as if he would be pulling a very large train even though they would be doing most of the work.
Once when his train was ready, Diesel took the disguised diesels and the trucks to Knapford, but blocked the entrance to the yard and prevented anybody from leaving or entering. As Diesel refused to move his train, Thomas decided to move it himself, but this resulted in an accident when the diesels mistook his whistle for Diesel's horn and pushed him out of the yard, causing him to crash into Norman. Diesel berated his lackeys at the Dieselworks, and as he was biffing Dart around, one of the crate disguises fell on top of him. Unable to see where he was going, Diesel began aimlessly roaming around the railway, while the diesel engines pursued him. Diesel was accidentally sent away on a ship when he was mistaken for an ordinary crate. (TVS; The Great Race)
Personality and Traits
Diesel is based on the BR Class 08. These diesel shunters were the most popular and successful diesel engines ever built, with over 900 of them being made. Today, over a hundred of these engines have been preserved. 'Arry, Bert, Splatter, Dodge, Paxton, Sidney, the Diesel Shunter and the Great Railway Show Diesels also share this basis.
Diesel is painted black all over with red bufferbeams. In the Railway Series and television series, his siderods were grey, but they became black in the sixth season.
In the nineteenth season, part of Diesel's coupling chain became red for unknown reasons. However, in The Great Race, Diesel's coupling chain went back to being black.
- Duck and the Diesel Engine Pop Goes the Diesel, Dirty Work and A Close Shave (mentioned only)
- The Little Old Engine - Rock 'n' Roll (indirectly mentioned)
- Diesel was the first diesel engine to be introduced in the Railway Series and Thomas & Friends.
- Diesel was originally going to appear in Edward, Trevor and the Really Useful Party. However, for unknown reasons, he was cut out of the episode. It is unknown what his role in the episode was going to be.
- In Misty Island Rescue, Diesel received a generic, American diesel horn. However, in Day of the Diesels, he regained his original horn sound, and his American horn sound was given to Mavis.