A month ago, my 2014 Mitsubishi Mirage decided to not start in the morning. It cranked and sputtered a little but wouldn't start. I had just moved to and was about to start a new job so I had no time to tinker around so I pushed the car down the block to a mechanic. He said that the cause was bad fuel, and had me smell a sample of the fuel that he pumped out of the tank, asking "does this smell like gas to you?" I'm no connoisseur of gasoline so I actually had no idea but he seemed to know what he was doing so I trusted his opinion that it the fuel was bad. I had filled up at a regular gas station in Middlebury VT the day before and I know I didn't accidently put diesel in the tank because the nozzle wouldn't fit in the gasoline car so it must have just been bad luck with the some layer of contamination fuel at the gas station that ended up in my car.

650 dollars later, the mirage was back in action, with a cleaned-out fuel tank and new spark plugs (the old plugs were original and the car had 100k km on it (60k miles) so it was due for a replacement anyway. If I wasn't stressed with moving and having to start a new job, I would probably have probably paid the diagnostic fee and then siphoned the tank and changed the spark plugs myself. My guess is that doing so and adding a bottle of fuel stabilizer would have been enough to burn through the residual bad fuel, although it might have come at a risk of ruining the emissions control systems if it didn't burn clean.

I hope nobody else encounters this problem but if you do, maybe this info will help troubleshoot.