my glow plug experience. last august with the temperature in the high 80s, my 300dt would not start. replaced the glow plugs and the bugger started. now on to january of this year. 8 degrees. car sat overnight. glow plug light on for about 10 seconds. hit the starter and immediate response. i be a believer in fresh glow plugs. oh, car has 290k miles. and a fresh battery.