diesel engine vs diesel motor

diesel engine and diesel motor both are nouns.

Word	Noun	Adjective	Verb	Adverb
diesel engine	Yes	No	No	No
diesel motor	Yes	No	No	No

As nouns, diesel engine and diesel motor are synonyms defined as:

diesel engine and diesel motor: an internal-combustion engine that burns heavy oil

Other synonyms of diesel engine include diesel.

diesel engine (noun)	diesel motor (noun)
an internal-combustion engine that burns heavy oil	an internal-combustion engine that burns heavy oil