The diesel engine on the Oliver 1850 is indeed a Perkins 354 and has been reported to be very fuel efficient, and being a six cyl is extremely smooth. I cannot tell from the picture if it has a over under direct drive or has the older system. If its the older system it has a knob on the dash, below the instruments as opposed to the shifter on the side of the instrument panel. If you have the older system shift it quick don't go slowly its hard on them to be between positions. Great tractor, comparable to a JD 4020, personal opinion it will walk away with a 4020. The cold start is a little interesting with the manifold heater instead of a glow plug, they work pretty well. I am currently restoring a Cockshutt 1850 which is the same tractor wih different badging and its red instead of green. If you should need information on the tractor feel free to give drop me a line, I have lots of info and manuals on the tractor.