2006 f-350 with 210,000 km. It has lost some power and chatters like its missing only when it's a little cold.Since this started my fuel economy drop quite a bit and there is a lot of blue smoke now.Any idea ?

You definitely want to check oil level and engine compression.

These links may help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-10.html#post1977241

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-8.html#post1415281

Once you solve the problem and make any necessary repairs, start using full-synthetic HDDO--you'll be glad you did.