The Dorman diesel engine business was bought in 1987 by Broadcrown and was later purchased by the Perkins Engines Company of Peterborough in 1993.
The last Dorman branded engine was produced in 1995.
In 1998 Perkins sold the Ruston & Hornsby range to RHL Spares Ltd following the closure of Dorman Diesels Central Spares Division in Lincoln. Formed by a group of experienced former Dorman employees to support the Ruston & Hornsby and Dorman Diesel engine ranges; RHL purchased the stock and rights to exclusively support the old Ruston & Hornsby range of engines. The RHL Spares business was purchased in 2006.
In September 2010 Perkins Engines agreed to sell all Dorman Diesels non-SE related parts business including the ST, DA,Q, J, L, LS, P, Y, Monair, F, and DWD engine ranges.