Day of the Diesels is a 2011 Thomas and Friends film.
After witnessing a new engine, Belle, extinguish a fire, Thomas and Percy shunt her to the Steamworks when she runs out of water. Once there, Sir Topham Hatt congratulates her, but says they need another fire engine. When Belle suggests Flynn, the matter is arranged to bring him over from the Mainland.
However, when Thomas starts to spend more time with Belle, Percy gets jealous and instead of delivering Flynn's hose to the Search and Rescue Centre, he follows Diesel to the Sodor Dieselworks, where he meets Diesel 10. Percy tries to leave so he can deliver the hose, but Diesel 10 arranges for Dart to deliver it. When Diesel 10 informs Percy that he informed Sir Topham Hatt about the state of the Dieselworks, but he didn't listen, Percy says he will ask Thomas.
Meanwhile, Flynn arrives at the docks and later arrives at the Steamworks, where everyone soon begins admiring him. Percy finds Thomas there and tries to tell him about the Dieselworks, but he says that Sir Topham Hatt asked him to show Flynn around the Island. Percy sadly goes to Tidmouth Sheds.
Percy arrives at the Dieselworks the next day and finds out that they don't have a crane. Percy goes back to the Steamworks to find Thomas, but he is not there. However, Kevin is and Percy tells him about his dilemma. Just then, Thomas arrives and tells Percy that Flynn's hose is missing. Percy once again tries to tell him, but he just ignores him. It soon grows dark as Percy tries searching for the hose and he returns to Tidmouth Sheds. When he finds Flynn in his berth, he goes back to the Steamworks and tells Kevin that he will take him to the Dieselworks. Once there, Diesel 10 is happy to have a new crane and the place is soon cleaned up.
When Diesel 10 finds out Percy has not told Thomas yet, he tells him to bring Thomas to the Dieselworks so he can tell him himself. Percy agrees and sleeps at the Dieselworks. Percy arrives at Knapford the next day and learns Thomas has been looking for him. Just then, Gordon pulls up and says that Kevin is missing. When Percy tells them where Kevin is, Thomas tells him that he should inform Victor. When Percy goes to the Steamworks, he tells Thomas that he has to get Kevin from the Dieselworks. However, when Victor finds out, he goes to inform Sir Topham Hatt.
Percy goes back to the Dieselworks and tells Diesel 10 that Thomas will be here shortly. When Thomas arrives, Diesel 10 tells Den and Dart to take him to the back shed and he then tells Percy to lead them to the Steamworks so they can take it over and Sir Topham Hatt will listen to them. Unfortunately, when Percy and the Diesels arrive at the Steamworks, Percy is horrified to learn that Diesel 10 has been lying to him the whole time and the Diesels soon cause havoc inside the Steamworks and Percy can't stop it. To make matters worse, when Percy goes back to the Dieselworks, he finds a fire in the main shed and races to the Rescue Centre for Belle and Flynn. However, Belle tells him that Flynn's hose is still missing and together, they set off for the Dieselworks.
When they arrive, they see Den and Dart holding Thomas and Kevin hostage and Dart tells Percy that Flynn's hose is in the garbage. The two soon run away when they smell smoke, and Percy frees Thomas and Kevin. Together, they watch Belle and Flynn successfully put out the fire. Then, they rally all their friends to take back the Steamworks. Once there, the steam engines make a promise to Diesel 10 that they will help him fix the Dieselworks if they give back the Steamworks. Just then, Sir Topham Hatt arrives, furiously berates Diesel 10, and orders him to fix everything he has damaged. However, when Percy, Thomas, and Kevin inform Sir Topham Hatt about the Dieselworks, he reveals it was his plan all along but things take time.
As soon as the Dieselworks is fixed, Sir Topham Hatt reopens the Dieselworks and says that it is special, considering that both steam engines and diesel engines worked together to fix it.
- Michael Angelis as the Narrator
- Ben Small as Thomas and Toby
- Keith Wickham as Edward, Henry, Gordon, James, Percy, Dowager Hatt, the Fat Controller, Den, Salty, Paxton, and Norman
- Matt Wilkinson as Diesel 10, Kevin, Stanley, Victor, Rocky, Cranky and Farmer McColl
- Teresa Gallagher as Belle, Emily, Mavis and Lady Hatt
- Kerry Shale as Diesel, 'Arry, Bert and Sidney
- Rupert Degas as Dart and Flynn
- This is the first appearance of Belle, Flynn, Den, Dart, Norman, Paxton and Sidney
- This special was released on DVD after ABC Kids aired Series 13 and before they picked up with Series 11, 14 and 15.