According to the dealer I use GM is recommending a new additive they are marketing for the Duramax. It is part number, 88861009, Conditioner, Diesel Fuel 325 ml (11 oz). Has anyone used or know anything about it? I have been using it for about 1000 miles. My fuel mileage did improve, I am now getting 18.9 city and 23 highway unloaded.

Anything anyone can add would be welcome.

Regards,
JimO