I have a 6.0 and I am using a winter fuel additive. We are currently in Brian Head, UT and so far no problems. However I have been plugging in overnight and the low has only been 16. Tonight and tomorrow night will be a good test since the low temp will be below zero and the high will only be in the teens . If there areany problems I will be sure to post again.
On a side note the van and new tires have been a champ in the snow.
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2007 Ford RB Diesel SMB 4x4 Pueblo Gold; Custom configuration (aisle layout); PIAA 580 driving lights; Picked up on Oct 19, 2007.
I have a 7.3l Diesel F350 that I've taken into some very cold temps without the block heater being plugged in. I've started it in single digit temps by running the glow plugs a couple of times, priming the gas pedal twice and starting it with a little gas. For some reason, my 7.3l likes a little gas when starting cold. Once it gets a little gas, it fires right up. I've definitely noticed a bit of a difference running the glow plugs a few times as opposed to once. You should be fine starting it with temps in the teens even if you aren't plugged in.