Hot plastic smell

[BLV]

I have a 2020 6.6 Duramax diesel HD. At random times, the fuel mileage will drop ( on the display) by about 8 miles per gallon. That lasts for about 20 miles or so , and then the fuel economy goes back to normal. When I get out of the truck I smell a hot plastic burning smell ( only when the fuel economy is not normal ).  Is the engine in the regen cycle?

[silveradosid]

yes

[redwngr]

Yes.

8 to 10 mpg 'less than expected' for current; driving conditions. 

Lasts about 20 minutes. 

 

Is the truck fairly new/low miles?

 

Typically the smell part disappears after the first few regens.

On a higher mileage one it is possible that there is a fuel leaking from the regen circuit that is resulting in the smell.

 

[BLV]

Yes, it’s got about 10K on it. Bought it new. Be nice if they told people that’s normal. I had it back to the dealership for this, but they couldn’t find anything wrong . Thank you for replying.