"Devious" Diesel, is a devious diesel shunter. He speaks with a Neutral English accent.
When the Diesel came on loan to the North Western Railway in June 1957, Duck was asked to show him around. Duck was unimpressed by the Diesel's claims of being "revolutionary" and left him to his own devices. As a result, the Diesel was made into a laughing stock by the trucks for trying to pull some rusty old trucks and failing spectacularly, and the Diesel blamed Duck for not helping him. The Diesel swore a vendetta, and spread rumors that Duck had given the big engines rude nicknames. Duck was sent to Wellsworth pending an inquiry into the matter, but the Diesel got too big for his boots and tried telling lies about Henry. He was found out and sent home in disgrace. Several years later, the Diesel was brought back to help on Thomas' branchline whilst Percy was being repaired. The Diesel tried to win Thomas and Toby over, without success, and after he destroyed several trucks 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. The Diesel, realising that Thomas was blocking his only way home, went to the rescue. Clarabel put in a good word for the Diesel, and he, although he returned to the Other Railway, is always welcome on Sodor.
Diesel was sent away, but returned when Duck and Percy needed help at Brendam in 1991. The Diesel proved to be as bad as ever and was sent away for good after shunting some trucks of china clay into the sea, but he mysteriously snuck back to give Mavis advice in 1962 and taunt Gordon about the triumph of diesel power on the mainland in 1967. It is possible that these events happened during the Diesel's stay, or that the Diesel returned at some stage with goods from the mainland.
After Thomas was sent to the Works to have his bufferbeam repaired in 1995, the Diesel returned to do his work. Diesel was nasty to Henrietta, Annie and Clarabel, refused to sleep in the Ffarquhar engine sheds on the grounds that it was "smelly", and blatantly refused to pull freight because it was "bad for his swerves". Diesel later called Toby cowardly for having sideplates and cowcatchers and claimed that one only needed to "toot and look them in the eye" to shoo animals. This, of course, was proved false when the Diesel tried to shoo an inquisitive bull. The Fat Controller discovered that the Diesel was sneaking about, but gave him a 2nd chance after the Diesel pulled freight and started to break down. The Diesel promised to change the error of his ways.
When Henry was derailed by some trucks in 2002, the Diesel was brought back as a last resort to do his goods work, but his attempt to prove his worth resulted in him falling in a barge, and he was sent back to the mainland yet again.
For reasons unknown, the Diesel returned yet again in 2003, this time to assist Fergus at The Cement Works. Diesel became jealous of Fergus' reputation as the "pride of the Cement Works" and concocted a scheme to make Fergus run away. The Diesel was partially successful - he managed to make Fergus abandon his post for a time - but was ultimately foiled yet again. Amazingly, the Diesel was not sent back this time round, and has remained on the North Western Railway.
Despite remaining tricky and devious, in 2004, the 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's old and clapped out, Ben about there was a monster inside a tunnel, and Thomas about the "Curse of the Cliffs" and make him scared at Halloween.
But in 2006, the Diesel proved to have a good side inside him when he told Emily about his record he made for shunting lots of trucks, and proved to Thomas that he didn't ruin the photograph for the billboard on purpose.
Although the Diesel made fun of James when he was painted pink in 2009, 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. However, the 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 the Diesel brought the load of slate for the school that he proved himself Really Useful.
Diesel is, in essence, the average pantomime villain. He is oily, malicious, devious, scheming and full of ideas to get revenge. It appears the Diesel has a good side in him, but one would still have to look deep to find it. He has a love/hate relationship with Dennis. He is friends with The Diesel, D199, Old Stuck-Up, Diesel 10, Splatter, and Dodge.
Diesel is based on a BR Class 08 0-6-0, built at BR Works of Crewe, Darlington, Derby and Doncaster in 1953, approx. 29 ft 3 in long. Over seventy members of this class survive today in preservation. They were in fact the most successful shunting engines in the world, with 996 of them built.
Diesel is painted in the black livery used by British Railways for shunting engines in the 1950s. His side rods before 1995 were grey; since 1995, they are black.
- Kerry Shale (UK; Season 13 onwards - US; S19 onwards)
- Michael Brandon (US; S13 - Blue Mountain Mystery)
- Martin Sherman (US; King of the Railway - S18)
- だいすけ ごうり (Japan; 第2-8シリーズ)
- ひさお えがわ (Japan; 第6シリーズ only)
- けん サンダース (Japan; みんなが一緒に来て！すべての乗り物に乗って onwards)
- Carlos Petrel (Mexico; Series 2 - 7)
- Blas García (Mexico; Series 8 onwards)
- Diesel's horn sounds like 1 horn blast.
- Diesel's siderods were originally silver, but changed to black in the 6th season.