My 96 X300’s mileage has dropped to as low as 15/16 mpg. Also I sometimes feel a kick in the transmission when I hit the gas pedal. I read that can actually be the car backfiring from a bad ignishion coil? Does this sound familiar?

 

The thermostat was stuck so after replacing the thermostat the mileage went back up. They did a transmission service which included replacing the transmission filter so hopefully it will shift smoothly now.