I have an '05 f350 that I just recently bought. It never smoked whenever I test drove it or after I bought it until last weekend I changed the oil for the first time. I used rotella t 15w-40 and a Fram oil filter. I drove it 10 miles to pick up a load that was about 1600 lbs and noticed as I was pulling away from a complete stop, my truck was blowing a big blue cloud out the exhaust. It only blows blue smoke when taking off from a stop through the first three gears. Talked to a friend and he said it could be coolant going through the engine. The truck runs fine when idling or cruising down the road. I have noticed the antifreeze has been dropped since i changed the oil.