There was a time where both my neighbor Heidi and i were on over nights, but opposites, meaning if i worked every sun mon tue overnight she worked at qa different site same company wed thur fri EO sat nights and both of us had vehicles that were not only old but had more things go wrong and we used to use each others vehicles all the time just to make sure we did not miss work when one or the others was broken down and as long as we were both insured no problem not against the law.