We receive calls frequently about renting a car. The first thing you must know is if you have a MA auto policy, it will not cover you outside of the US and Canada. So you if you travel outside of these two countries, either (a) avoid renting a car; or (b) buy as much insurance as possible (liability and physical damage). Keep in mind that laws are much different in other countries.
If you are renting a car (short term, personal use) in the US or Canada, your policy’s liability (umbrella recommended) and physical damage (collision and comprehensive, if you have it) will “follow” you. However, your auto insurance company may NOT pay for (a) the rental car company’s loss of use of the rental vehicle if it is damaged (the rental car company’s ability to rent the car to others while it is being fixed); and/or (b) the full replacement cost of the rental vehicle if it is damaged (your policy pays for actual cash value – which includes depreciation – while the rental car company will need full replacement cost to buy a replacement rental car).
Due to the two limitations, (a) loss of use and (b) replacement cost, you should purchase the physical damage coverages (often referred to as “LDW” and/or “CDW” offered by the rental car company). These costs can add up but if you are ever in an accident they are well worth it.
Lastly, you must inform the rental car company of all operators ahead of time and make sure you stay on public roads.