The only dmus I can remember on the line were class 114 which were much used in Lincolnshire.
Details of all the locomotive types used, from the construction of the line onwards, are given in the book 'The Lincoln to Grantham Line via Honington' by Stewart E. Squires, published by The Oakwood Press in 1996.
I was born in Caythorpe and can just remember steam-hauled services but not the types of locomotives used. However, the above book indicates that prior to dieselisation in 1956 passenger services were often worked by B1s, B12s and A5s. Also appearing on goods services were J39s.
As mentioned, the line was often used for diversions and whatever types normally worked the east coast main line were able to be used without restriction as the line had been brought up to main line standards prior to World War ll.