Very good point about the gas. Could of got some water in the tank from a bad gas station. I use to work for 7-eleven Dispatch and let me tell you, everyday we got about 100 calls from gas stations with their "veederoot" alarm going off telling them they have excessive water in the tanks. Its a very common thing. If you go to a gas station and go inside before you pump, check to see if you can read the "veederoot" behind the counter. If you see red lights flashing or hear a buzzer from the machine...don't get gas there. That means there tanks have more than 6 inches of water inside. Usually the tanks have pumps that rid them of water but sometimes they don't.

Could also be other things like sand, leaves, salt, or maybe even sugar. Sugar usally kills a car period. Maybe someone doesn't like your girlfriend very much. Or her Volvo for that matter.
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-Brandon at home '88 744ti 139k miles