2016 2500 Duramax Fuel Milage

Marc Russ · November 21, 2016

How do you tell when it goes into a regeneration?

Colossus · November 21, 2016

RPMs go up when at a stop or in park.

Cowpie · November 23, 2016

Nice to hear. It seems GM does pretty good with it's oil life monitor, tire pressure monitor, & now fuel economy monitor devices. You hear that, GM? WAY TO GO! See? You guys CAN do some things right! Drinks all around!

They may have done alright with the OLM and TPMS, but I use neither of them. Still haven't found the sensor that determines that my pickup gets operated several miles a day on dusty gravel roads and lets the OLM know this, so until I do, I change the oil at 5000 miles. As for the TPMS, I deflate tires to 55 when empty or light loaded, and only air them up to 60 front 70 rear when I know I will be piling on the weight. So both OLM and TPMS is a moot issue with me. I just ignore the nanny TPMS light. Just something else in a list of things I had to pay for that I have no use for.

Colossus · November 23, 2016

I don't think there will ever be a sensor that determines what the conditions are of the road you drive on, but in general and as a general rule of thumb, the OLM does it's job for the parameters it does measure.

But when all else fails, 5000 miles /once a year works just fine too.

Cowpie · November 24, 2016

I realize that the move has been on for some time to extend oil drains by both consumers and OEM's, but it is not without its flaws. My 2006 Cadillac CTS 3.6L is one good example. First off, GM admitted they goofed on OLM programming and had the engines going twice as long as they should have on oil changes. Well after many timing chain failures, oil consumption issues, ad nauseam, we all learned. And No one should trust blanket OLM guidelines without confirming that the particular oil they are using is holding up well in that time frame. Different oils have different chemistry, even if they are the same API class or even dexos compliant. I have extended the drains on my commercial heavy trucks by about 50% beyond the OEM guidelines with excellent results, but it is with a stack of oil sample results confirming things and even using several brands of oils to find out which worked best with my engines. The OLM is algorithm only. No actual testing of oil. And it assumes a lot that may not always be true.

But oil sample testing may not be in most people's game. But on a expensive vehicle and engine like the Dmax, I am not sure how spending $10-$15 bucks on a used oil sample is going to be a wallet buster. I can get oil kits and analysis from my oil suppler, as can anyone else, for about $10. I recently saw Wix filters has their own sample kits and analysis going for about $12 on Amazon.

And even among CJ-4 class oil that the Dmax uses, there is a wide swing on oil and additive package makeup between differing brands. And how that works well in one's engine also varies widely. Think that all CJ-4's are comparable? Then mosey on over to the Petroleum Quality Institute of America website and see the results they have gleaned. From my own experience, almost 5 million miles of it, with commercial diesels of varying sizes and applications, engines will show a favoritism to a particular brand of oil.

ShotgunZ71 · November 24, 2016

Just took the truck on an 850 mile trip. Interstate driving, speeds generally 75-80. I averaged 20.4 mpg for the trip. Very happy with that considering the speed. I have noticed if speeds stay around 70-72, the mileage is a mpg or so better.

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Debra in Cali · November 26, 2016

Just keep in mind that that 100 miles to empty can quickly take a nosedive if your truck goes into a regen. Don't ever let the thing go below 1/4 a tank.

That is especially true when pulling a behemoth. Was running a little light on the way home with our new 5th wheel. Traffic on the freeway was at a dead stop with Onstar telling me accident ahead. Bailed on the freeway idea and used surface streets. Wouldn't you know it. Hit a red light every time. My husband was cracking up. But we were moving faster that way than the freeway. By the time I got home I was really low.

Colossus · November 27, 2016

Why would OnStar be telling you there is an accident ahead?

revrnd · November 27, 2016

I have extended the drains on my commercial heavy trucks by about 50% beyond the OEM guidelines with excellent results, but it is with a stack of oil sample results confirming things and even using several brands of oils to find out which worked best with my engines. The OLM is algorithm only. No actual testing of oil. And it assumes a lot that may not always be true.

Did Delphi ever bring to market a oil "checking" sensor? I recall reading in a commercial trucking magazine (new products section) back in the late 80s/early 90s that this sensor (placed in the oil system) would measure the dielectric of the oil. I may have the numbers reversed, but you'll get the point. New oil has a dielectric of 1 as it degrades, it gets closer to 0. At a pre-determined measurement, the PCM would alert the driver.

EDIT: Looks like they've refined it:

http://www.autoblog.com/2007/01/20/delphi-announces-new-oil-condition-sensor-for-diesel-engines/

Marc Russ · November 28, 2016

Just filled up and these are the results:

DIC set to last 400 mi. = 16.7

Trip B set to 400 mi. = 17.2

Actual fill up after 400 mi =14.5.

My usual drivng loop is about 30% 45 mph with a few stops and 70% around town with normal traffic, stop signs and various stops.

I'm short more than 2 mpg between actual and the most conservative DIC measurements. Had it a month and haven't had the chance to go much faster than 55 mph yet.