HELP! Our newly purchased Duramax Hummer
 

Started making black smoke on a hill! Even on some fairly mild hills @ 70 MPH. Edge programer was set on economy.

we have owned it only 2 weeks, never did that before. only 9K miles on the Duramax. Then it started running normal again and has not done it in the 70 miles home. EGT was 1100-1200 during the smoke.

truck has ONLY been run on B99 since engine was new. we mixed in about 75% dino diesel shortly before the smoke issue???

It never smoked on B99, but it did after a mix of #2 and B99??

True. But it did not start smoking when we added #2 and has not smoked since that one incident. Lasted about ten minutes. We then continued our trip back to LA from Tehachapi (including some steep hills)

So it stopped after #2 was added?? Might have been some thicker veggie oil being burnt before the #2 had a chance to thin the mix out.

no. it did not smoke during hills/mountain driving UNTILL we ran some #2 and then it only did it for about ten min. on some hills. VERY black smoke and alot!

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sounds confusing. It never smoked for 300 miles or so ON B99. Then shortly (2 days) after adding about 80% #2 it had the smoking incdent. is that clearer?

Might have been some stuff that got separated out when the #2 and B99 mixed. I would recommend changing out the fuel filter(s). But after she cleared it's throat, so to speak, still runs strong??

possibly, but I thought it was an issue when you have been running #2 and then start Bio. This truck has been running B99 since new and has THREE fuel filters two of the are FASS?? Yes it is running strong again. Also we are only showing about 10-12 MPG on economy setting. Predator motorsports says we should be getting close to 22MPG. maybe another issue?

what year dmax motor is it?

or is it the 6.5?

It is a 6.6 I belive. With only 9K I would think 2006-2007

It you could please find out for sure. This way we can move to the proper forum. TIA. It have a little bigger/flatter front end have bigger headlights?? If so it's an 07 and up.