Collocations for economical - adj.

be, seem
Solid fuel would be more economical.

extremely, fairly, very, etc.
highly, remarkably
This new oven is highly economical.

in
This arrangement is more economical in its use of staff.

of
more economical of time and resources

with
This arrangement is more economical with space.

economical with the truth
She accused him of being economical with the truth (= not telling the truth).