I have a 2006 Ford F350 with 6.0 Diesel. The vehicle is serviced on a regular basis. By the way just turned 109,000 miles. I recently developed what seems to me a slight miss. Rough idle. And when maintaining steady speed and in 5th ? Gear, automatic tranny. If I push the accelerator and tranny downshifts to next gear, engine smooths out. I have changed fuel filter twice and air filter checked good at last service at my Ford Dealer. Fuel quality is good. Was running great and just suddenly started jerking and running rough. Any helpful comments will be appreciated. By the way, when running properly can't be beat. Thanks.

Many diesel owners are experiencing problems in cold weather with ultralow-sulfur fuel. It tends to gel, clog fuel filters, and cause problems with fuel injectors. Consider adding Amsoil's diesel fuel additive to your fuel. Bought in bulk, it will add about a nickel to the cost of a gallon of fuel. It does a great job of cleaning injectors, valves, and the complete fuel system. Naturally, it helps keep fuel from gelling.

The problem comes during the refining process used to attain the ultralow-sulfur ratio. That affects the naturally occurring wax in diesel in such a way that it can cause the fuel to turn from liquid to gel more readily in cold temperates. Gelled fuel clogs the fuel filter and starves the engine, causing it to stop. The EPA says there is nothing wrong with the fuel. But it may have to be treated with special additives.

I've worked on the 7.3L PSDs and would recommend that you use synthetic diesel engine oil, in conjunction with a bypass filter. These are awesome trucks. Next time you change the transmission fluid and filter, consider using either the Amsoil Universal Synthetic ATF or the Mobil 1 Synthetic Multi-Vehicle ATF. The results I've experienced on F350s have been very impressive.