fuel temperature sensor

Gasoline will still burn down to -45C (-49C) for use in a combustion engine. It will still burn down to -72C (-97F). The aromatics don't freeze until -129C (-200F). I'm not sure where the heavy hydrocarbons begin to gel but it's probably at various temperatures below its burn point. So where have you ever been when it's been that cold? Coldest I've hit was -45F but the coldest recorded temperature in Antarctica was -88.27C (-126.9F). However, at that low a temperature, your battery won't start the car even if it was warmed because the engine oil is so thick that your engine parts would be stuck together. You'd have to thaw out the car before you could start it (so fuel temperature is not the issue) and then constantly leave it running. Its autoignite temperature is 246C (479F). If your gas tank experienced that temperature, you'd already be a charcoal lump inside a scorched vehicle, so stop parking next to the space shuttle on takeoff.

If you have water in your tank, it will still freeze at 32F (0C). There is no heater to warm up the gas so air temperature will tell you what is your gasoline temperature. Unless you are splashing through puddles to then have the evaporation cool your gas tank, the "fan" of driving your car around still means the gasoline is at air temperature (inanimate objects don't care about wind chill or wind heat at the speeds that your car will be traveling).

There's probably good reason why no one bothers monitoring the gasoline temperature. If it's too cold to burn well enough to run the car, you'll have other bigger problems. If it's hot enough to self-ignite, you also have far bigger problems. If you know your air temperature, you know the temperature of the gas in your tank. I suppose some heat might get picked up from the exhaust pipe but if cars were exploding because exhaust pipes were raising the gasoline to its auto-ignite temperature then insurance would be so suicidally high that no one could afford to drive (well, maybe Bill Gates could still drive around). If you're concerned about water freezing in the tank or supply lines, the air temperature will let you know when it's possible.

I think its part of the fuel gauge pickup - not sure.

Carl