Originally Posted by itguy08
Originally Posted by 02SE
Originally Posted by dareo
Their claim that the GM only used .6 liters vs Ford and Rams 2.6 2.7 liters is cause to throw out their entire set of data. Those trucks are going to get very close to each other in fuel economy. Real world results would be 5-10% of total variation between the three diesels. At least TFL will run a 98 mile loop and show the results.
As you point out, anyone that can't see there is obviously some flaw in their data gathering and reporting, is in denial, a super fanboy, or simply clueless. Similar weights, similar power, two are within a tenth of a MPG, and one supposedly uses a mere fraction of the fuel? Yeah, there's either blatant bias, or just incompetence in their methods.
Had you both bothered to actually read the link you'd see where they do explain how the dyno runs worked and how the GM posted the same #s twice. Given Truck Trend is a pretty respected magazine (and the results somewhat back up pickuptrucks.com's tests in that the GM is the most fuel efficient), I think they know a little bit of what they are doing.
Quote
The first two tests of our six-event throwdown pitted our three factory-stock 1-ton duallies against ATS Diesel Performance's vicious dual eddy-current Mustang dynamometer. Before getting down to the nitty gritty of just how much power these monsters put out, we first ran them through a fuel-economy evaluation utilizing the dyno and its powerful software. Similar to how the EPA does its fuel-economy testing, our evaluation began by strapping each truck to the dyno. We then topped off the fuel tank using a metered dispenser and set off on the 22-minute test. Over the course of a simulated 7.2 miles, the dyno is able to vary its load to simulate a diversity of terrain and driving conditions, and the vehicles run from stopped at idle all the way up to 60 mph. The system tells the driver what input is required by displaying a green arrow that must be kept between a pair of lines on a nearby monitor. Think of it as the most stressful, tedious video game you've ever played. Upon completion and before leaving the dyno cell, the trucks were again topped off using the metered pump, and the amount of fuel used was recorded.
To eliminate the human factor as much as possible, we tapped the driving talent of ATS's Maximillian Edwards, resident dyno guru and head of the company's electronics shop. Max made it through the test with no faults, but a pair of anomalies on the first test led us to run all the trucks through a second time. During the first test, the Ford F-350 went into its exhaust-regeneration cycle, thus tanking its fuel-economy result and voiding the test. The second anomaly came when the GMC Sierra Denali 3500HD used a significant amount less fuel than the other two, leading us to wonder if we'd done something wrong. After a second run, the Sierra backed up its first number and took the win in our fuel-efficiency challenge by a wide margin.
Certainly not scientific but neither is resetting the fuel computer and using that as TFL uses to calculate their MPG #s. The dash computer is great at averaging over long periods of time.
Not sure any of this matters - the OP doesn't want a Diesel and wants to stay in a GM vehicle, which by all accounts is one of the top pickup trucks.
So you really believe the GM used ONE TENTH over a half gallon, while the other two used two gallons more? Their testing methodology is flawed, but they apparently lack the expertise to determine why.
As dareo said, TFL uses the same pump and filling method every time for their 98 mile loop, and hand calculate the fuel economy for each truck they test. The newly revised for '17 Duramax is much better in fuel economy than it was prior the engine overhaul. So much so that it's usually right there with the Cummins for fuel economy. It's a shame GM hasn't redesigned the entire truck to be able to compete with Ford and RAM in the heavy towing arena. Maybe that's in their plans for the supposedly redesigned 2020 truck.
