I'm useless with car repairs but I don't want to get ripped off. My 2011 advenger with 82k miles V6 automatic over heated yesterday 1 1/2 miles from my home and beside an oil fast lube place. The oil change guy said my coolant was a gallon low? (He just added fluids 3 weeks ago with my 3000 oil change). Also he ordered a thermostat to put on it Friday. I drove it back home. I'm not 100% comfortable with these mechanics, why would the coolant be that low? My other question, he said we'll "start" with the thermostat & see if that fixes it. Does that even sound right? Thanks