You must contact the dealer to document the problem. On numerous car forums for different brands, people notice the smell of gas during startup. Sometimes it’s an actual problem – a leak of some kind, and other times there’s no apparent problem other than the smell itself. Unless you let Subaru take a look, there’s not much point in speculating.
Document each time it happens so that when you take it to the dealer you have a record of the circumstances, eg. cold start in the morning.
The dealer will inspect the fuel system, check the codes, and if they find nothing, they will try to replicate the problem. The more details you give them, the more likely they are to discover the same issue. If the problem is intermittent, like only once a week, then it will be difficult for the dealer to replicate unless there are some conditions that are different at that time – for example, filling the tank the day before, or the tank it was almost empty, or the temperature was below freezing, or you used a block heater, or the car was parked on an incline at the time, or the car had not been driven for 36 hours. Any possible set of circumstances that will allow the dealer to duplicate the problem will help them diagnose it.
Hoping it won’t happen to you again, but if it does, you have to accept it. It is not a normal starter smell in the Subaru XT, nor is it a known problem that they can easily diagnose, but Subaru is aware that some customers have had this problem in the Subaru Ascent, which has the same engine. I don’t believe they have singled out a single cause yet, so again any documentation you provide could help them figure out what’s going on in yours.
