diesel motor vs diesel

diesel motor and diesel both are nouns.

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

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

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

Other synonyms of diesel motor include diesel engine.

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