I have been looking for a class4 truck and yesterday I might of found the truck I wanted. Its a 99 ford F450 with the 7.3 PS. 15ft flatbed dump. The truck has 184000 miles. Has had a new rearend, new 6sp tranny, new injector pump, new brakes. 1st problem. It was cold, around 45 degrees and the truck hadnt been cranked in at least 2 months. Of course it was hard to start. After a boost, she finally fired up. 2nd problem. Once cranked, it wouldnt run above 1000 rpms. 3rd problem, after warming up some, (just a couple of minutes), the rpms started to climb, but not significantly. Decided to drive it up the road. Went about a 1/4 mile and turned back, truck wouldnt pull itself enough to get up to speed. 4th problem. Parked truck and seen something leaking out the bottom of engine. After quick check, it looked to be coming from the drain line on the fuel filter, but it didnt look like diesel fuel. A sniff test also said, this isnt diesel. I caught a little in a cup and it looked real oily like hydraulic oil, but it didnt look exactly like hyd oil. The whole time I was looking I let the truck run, it finally got to where it would rev up like a normal diesel should, but I didnt drive it anymore. I took the cup of oily substance up to the owners shop and asked what is this. His reply, bio diesel. He runs biofuel during the summer months and then changes back to a diesel/ biofuel mix for the winter. His claims are that the biofuel probably jelled because of the cold weather and was the reason for the hard start and no pulling power. He is going to suck out the bio diesel and replace with regular diesel sometime this week and I am going for another test drive. My 1st question is, does anyone here run biofuel in their diesel truck, and if so, does the above described sound like a problem you would expect in cold weather. 2nd question, Will a simple tank drain (refilling with diesel),and filter swap be all that is needed to correct the problems described above. Might as well ask, is $12000, a decent price for this truck. Body looks good, interior clean, dump looks and works good. AC is cold. All I can really see is it needs a set of rear tires.