“Economic” and “economical” are two 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.
So, government policies to do with finance would be economic but fuel-efficient cars would be described as more economical.
The main confusion arises when writers use “economic” when they really mean “economical”. Take, for example, the phrase “economical with the truth”, a euphemism for lying brought into popular usage by the British civil servant Robert Armstrong.
Armstrong used the phrase correctly, but many do not, referring instead to being “economic with the truth”. A simple web search will reveal many thousands of instances of this phrase, although it is essentially meaningless.
In colloquial English, the distinction between the two words is often blurred, but it is always useful to know the correct meanings.
As an aside, the adverb for both words is the same: economically.