Monthly Archives: July 2016

Ram fuel economy data

Back in May, I bought a “power adder” device for my truck: a DiabloSport Power Puck. By altering the sensor data the truck’s computer receives, it allows you to select an increased amount of power via a three-position switch: stock; +60 HP / +100 lb-ft torque; and +90 HP / +180 lb-ft torque. I got it used on eBay and it required some repair work to get it going.
Now that I’ve collected the same amount of fuel economy data post-Power Puck install as I had prior to it, I decided to do some statistical analysis. My truck is a 2003 Dodge Ram 2500 with the 5.9L common-rail Cummins turbo diesel engine, and a 6-speed manual transmission.
The raw data are below, but the results are, in summary (note that these are hand-calculated numbers, not what is reported via the overhead fuel economy meter):
Average fuel economy pre-PP: 18.03 mpg
Average fuel economy post-PP: 18.3 mpg
Is it a significant increase? Who knows. I don’t have enough data to feel I can draw that conclusion. But I am seeing slightly improved fuel economy, while at the same time having a lot more power when I want/need it. The advertising seems to be accurate; the question is whether it’s worth getting one simply for the increased fuel economy. I suppose if you keep your truck for a long time and/or fuel prices are high, it might be. But most people want these things to make their trucks perform better, and any improved fuel economy is just a bonus.
Further conclusion: while the overhead fuel economy meter has always been inaccurate, the Power Puck has worsened its inaccuracy by a factor of four. Prior to the Power Puck, the “lie-o-meter” was fairly consistently and optimistically wrong by about 3.16% (meaning, it was reporting fuel economy that was an average of 3.16% higher than it actually was). After adding the Power Puck, it has continued to be consistently optimistic, but by an average of 12.57%!


7/14 overhead 18.8 actual 17.27 error +8.86%

— Replaced fuel filter on 7/11 but only drove ~100 miles with new filter

7/4 overhead 21.2 actual 18.04 error +17.52%

6/28 overhead 20.5 actual 18.98 error +8.01%

6/6 overhead 20.8 actual 18.29 error +13.72%

5/26 overhead 21.1 actual 18.40 error +14.67%

5/11 overhead 20.6 actual 18.23 error +13.00%

5/4/16 overhead 21.5 actual 18.85 error +14.06%
(first full tank with Power Puck)

— Start power puck

11/21/15 overhead 19.5 actual 16.98 error +14.84%

11/7 overhead 19.9 actual 18.44 error +7.92%

10/1 overhead 19.0 actual 18.05 error +5.26%

9/17 overhead 18.4 actual 21.8 error -18.48% (?!)

9/6 overhead 18.7 actual 15.95 error +17.24%

8/30 overhead 18.0 actual 17.12 error +5.14%

7/1 overhead 17.6 actual 17.33 error +1.56%

5/21 overhead 17.7 actual 18.56 error -4.86%



Average overhead mpg prior to power puck: 18.6

Average actual mpg prior to power puck: 18.03

Average error between overhead and actual, prior to power puck: +3.16%

Average overhead mpg after power puck: 20.6

Average actual mpg after power puck: 18.3

Average error between overhead and actual, after power puck: +12.57%


Ram: Oil and filter change; fuel filter change

207,048 miles, 7/11/16.

I replaced the fuel filter (with a Baldwin PF7977, which does in fact fit even though Amazon thinks it doesn’t). The old one was dirty, though I don’t know how much of that was dirt and how much was just trapped dye from the 2-stroke oil. There is a marked increase in acceleration with the new filter, so I guess I ought not wait as long between fuel filter changes (this one had at least 21,000 miles on it, as it couldn’t have been replaced earlier than when I bought the truck from Unique — and maybe it even had more miles than that).

People on the forums say to change the fuel filter every other oil change. For $15, it’s a good way to preserve injectors and the injection pump.

Changed the engine oil (with plain Valvoline diesel 15w-40) and filter (Baldwin BT7349 — again, Amazon says it doesn’t fit but it does).