1. Have you tried this new liquid soap for the washing machine. It’s very economical. It lasts for ages.
2. I used to have a Smart car. It didn’t go very fast, but it was very economical on petrol.
3. The economic policies of the present government are ruining the country.
4. Pepito studied economics at university and he’s an expert in economic matters.

economic = económico (relativo a la economía)
economical = económico, barato, rentable