After Sir Topham Hatt's death, Rudolph Diesel had struck a deal with Alfred Herman, which brought Diesel 10, Andy, and a whole bunch of other diesels to the North Western Railway, much to the steam engines worry and dismay. Not long after Andy had arrived on Sodor, Diesel 10 tried to convince the other diesels not to trust the steam engines, but the diesels remained doubt, especially when Paxton questions on what 10 said was true or not, but after Andy told the diesels about the first time he and Diesel 10 first came to Sodor, the Oiler Committee was formed and both Andy and Diesel 10 became the leaders.
During the events of "U.K. Trip", Andy rallied the other diesels into taking over the Sodor Steamworks, and kicking Victor out, and violently shoving Gordon out when he came to investigate with Andy telling the big engine that the Steamworks was theirs now.
After Toby's death, while the other diesels were still celebrating over their takeover of the Steamworks, Andy went out as the other diesels had given him quite a headache as Percy came to confront Andy about him being Mr. M. Andy laughs at this and gives the green tank engine a haunting speech about the future of steam engines. After this Diesel was purswaded to join the Oiler Committee, much to the confusion of Simon Johnson of a diesel being in the Steamworks, eventually when BoCo and Mavis went into the Steamworks, Simon walked in and found out that he and Andy had a lot in common, and both became partners. That night while the steam engines were asleep, Paxton and Bert came and kidnapped Edward, and took him to The Scrapyards and scrapped him, but Diesel feeling this isn't right, leaves and talks to a still traumatized Den about what he was doing was right or not. This was then when Den regained his ability to speak, and tell Diesel that Simon and the Blockade Committee was responsible for the Sodor Dieselworks fire, and the death of Derek which caused the black shunter to switch to the steam engines side.
As the engines declared it no longer safe at Tidmouth Sheds, decided to leave and seak refuge with the Skarloey Railway Engines, unknown that they were being watched by D199, who later told Andy, and he and 'Arry went down to check to see if it was true. Days later both Andy and Diesel 10 found the remains of Lady and decided to tourcher the engines more by presenting Lady to them and saying that it would soon happen to the other steam engines. Duke enraged by this orders Andy and Diesel 10 to leave him and his friends alone, the two satisfied with themselfs, leave through the tunnel back to the scrapyards to continue breaking up Edward, with the aid of Mr. M. But both BoCo and Mavis decided they didn't want to be apart of the Committee anymore, but Andy and Diesel 10 didn't take this lightly, and using Pinchy, Diesel 10 began ripping Mavis' sideplates off while BoCo fleed in fear.
After a few more days, Diesel 10 and Spamcan crepted in and kidnapped Percy and took him up to The Quarry as a plan to scrap more of the steamies. Thomas and Gordon went to look for Percy, only to find Splatter, who had been placed by Andy, to trick the two engines that he betrayed The Oiler Committee to going up to the quarry to find their friend, only to realize too late that it was a trap and Gordon was captured and dragged away leaving the two tank engines trapped up in the quarry.
In "Nocturnal Intervention", Phil Aardman, along with Oliver and Toad, go out to look for the three engines, when Phil finds Thomas and Percy, he decided to buy the two tank engines time by using dynamite to blow up the entrance to the quarry, the explosion catches the attention of the diesels, and 10 and Spamcan went after them to see what the noise was. During the events of "Phil", after spying on 10 clearing the entrance to the quarry with Scruff, Phil had made one last plan to rescue Thomas and Percy, but as Percy was derailed, Phil could only take Thomas to safety, but unfortunately it all went wrong as Thomas hadn't been moved in days, he ran out of water right on the viaduct, and Diesel 10 who had been following Thomas, captured him and took him back to the Scrapyards much to the delight of Andy. When Phil asks Andy who Mr. M was, Andy and the other diesels reveal that Mr. M had been helping them all along as he was a forgotten father of the North Western Railway and would witness the end and rebirth of Sodor, before Andy had Simon take Phil away to kill him, and watching Thomas finally cry.
In "Authority" The Oiler Committee had come up with one last plan to get rid of the steam engines once and for all, by having Mr. M plant a pressure activated bomb onto Dodge's engine and use him as a suicide bomber to blow up the remaining steam engines, but unfortunately for both Andy and Dodge, Diesel who had been forced to leave earlier by James, overheard this plan and realizing he had to save the steamies, sacrificed himself by blowing himself, Dodge, and Andy up to smithereens. Meanwhile as BoCo with Annie and Clarabel, to the Scrapyards with Phil and General Robert Stewart and many solders, Diesel 10 and the remaining diesels and Mr. M are prepared to scrap Thomas, but Thomas tries to reason with Mr. M that he shouldn't force modernization and just let the steam engines be replaced in time, this makes Mr. M reveal himself to be Rudolph Diesel and gives a speech on how he couldn't reason with Sir Topham and decided to enact his vision for Sodor, and his about to start scrapping Thomas, when BoCo arrives and Diesel is placed under arrest ending the Oiler Committee once and for all, while the mess on Sodor is being cleaned up, Phil puts the diesels to work cleaning up and repairing the damage they had done to Sodor before sending them all away, where Splatter, D199 and Dennis are is unknown, while Diesel 10 was sent back to Ireland reuniting him with Bash, Dash, and Ferdinand, and allowing Paxton to stay on Sodor with 'Arry and Bert, and Diesel's remains along with Edward, Gordon, Lady, and possibly Andy and Dodge's remains were melted down and made into the Diesel Statue for Maron Park to honor those who had lost their lives during the conflict of 1945.