Black smoke from the tailpipe

[Texasbull]

I have a 2007 6.6 Duramax. Less than 9,000 miles, mostly highway. Today I noticed a steady black cloud blowing from my tailpipe, during acceleration the smoke became white/blue. This happened at 70-75 mph. When I dropped below 60-65 it stopped blowing. No loss of power, no rough idle and no changes in gauge levels. When I stopped and ran the rpm's to 1,800 no smoke. Only at freeway speeds. Any ideals what the problem is.

[madmatt]

have you noticed a loss in fuel economy??

[Texasbull]

I have averaged between 16-17 mpg. The computer is currently showing 15.8. Since this incident I have not had the chance to notice a change

[Mark Rinker]

Are you running any performance tunes, or stock?

Check for plugged or collapsed air filter, or blocked inlet tube. Sometimes these things can happen under high air demand - and spring back to normal at idle. Look carefully for signs of flex in all inlet tubes.

[Texasbull]

No extras all stock

[DmaxMaverick]

LBZ or LMM? If it's an LMM, it could be due to a DPF regen.

[Texasbull]

It is an LBZ engine