"economical" is a quality of a person, machine or process which uses resources efficiently. "The new Jaguar is very economical in its fuel consumption." "economic" is the adjective relating to "economy", in all its uses. Both words share one adverb - economically.

well , both of them are adjectives that are frequently used interchangeably. They are clearly related but they have, strictly speaking, quite distinct meanings. According to the Oxford English Dictionary, the definition of economic is Relating to economics or the economy. Economical, however, means Giving good value or return in relation to the resources used or money spent; sparing in the use of resources or money