I have a f-350 crew cab with 6.0l engine. We have done everything to keep it from blowing out smoke from the exhaust. Any ideas?

The links below should 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-46563-10.html#post1921427

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

Be sure to only use full-synthetic HDDO--it makes a huge difference with diesels.