Agreed, don't do that. Get the correct part for the job.
Regarding the automotive relays, look out for the voltage rating on the contacts if you're switching anything above "automotive" voltages (12-24V) and their current rating with respect to AC and DC - which ever you're switching. Switching (interrupting) high DC currents is a lot harder than AC-currents.

Is it AC or DC? If AC, single phase or 3-phase? What voltage is it?