diesel motor vs diesel engine

diesel motor and diesel engine both are nouns.

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

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

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

Other synonyms of diesel motor include diesel.

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