Adding DEF, Breaking Down the Cost - 2014 Ram 1500 EcoDiesel Long-Term Road Test
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2014 Ram 1500 EcoDiesel Long-Term Road Test

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2014 Ram 1500 EcoDiesel: Adding DEF, Breaking Down the Cost

August 19, 2015

2014 Ram 1500 EcoDiesel

A few hundred miles into my road trip with our long-term 2014 Ram 1500 EcoDiesel, the truck's DEF needle dipped into the red. So somewhere between Roswell, New Mexico and Austin, I stopped at a big travel center/truck stop/gas station that had DEF on tap.

Back home in Santa Monica, DEF pumps aren't easy to find. The closest stations to our offices are 15-20 miles away, so we've been using the various-sized boxes to fill up the blue stuff. But out on the open road where diesel big-rigs are king, diesel exhaust fluid is everywhere and when you aren't buying by the box, DEF is much, much cheaper.

When I pulled up at the pump, there were a few things to figure out. There was a big plastic shield covering the DEF pump (probably so you don't confuse it with gasoline) and a selection process on the keypad that had me buying "Reefer" on the company credit card. I'm hoping the boss doesn't look too closely at that expense report.

Otherwise though, it was just like pumping fuel: put the pump in, pull the handle, stand around and wait until it's done. It was much easier than ordering a box online, waiting for it to come in the mail, unscrewing the top, installing a spout and then having a bunch of cardboard waste when you're done.  

2014 Ram 1500 EcoDiesel

DEF was $2.80 per gallon at this station which is on par with the national average. For reference, the next-cheapest DEF purchase we've made was when we bought three 2.5-gallon containers from Amazon.com for $33. That works out to $4.40 per gallon. Clearly, it pays to find this stuff at the pump.

With that fill, we had added DEF to the Ram seven times over the last year. Here's a breakdown:

Date

Mileage

Gallons

Cost

 Per Gal

7/9/2014

5,542

1

$7.55

$7.55

7/11/2014

5,760

4.5

$21.00

$4.67

8/11/2014

8,975

6

$58.50

$9.75

10/25/2014

15,748

7.5

$33.00

$4.40

11/30/2014

21,083

6

$40.47

$6.75

3/18/2015

27,941

7.5

$35.91

$4.79

7/26/2015

36,363

6.275

$17.56

$2.80

Over 36,363 miles, the Ram has consumed 38.775 gallons of DEF. Since the last fill-up, we've averaged 1,342.1 mpg with DEF and the lifetime average now stands at 937.8 mpg. In other words, we are using about 10.6 gallons of DEF every 10,000 miles.

If we'd done every DEF fill at this pump with a price of $2.80 per gallon, our lifetime DEF cost at 36,363 miles would be $108.57. As it stands, we've spent $213.99. Not a life-altering difference by most standards, but definitely a gap. With these numbers in hand, I started wondering what the cost difference between our diesel-powered Ram and the two available gasoline-powered engines would be.

When I filled up on DEF, the Ram's lifetime average for fuel economy was 22.4 mpg, compared to its EPA-combined rating of 22 mpg. So for the purposes of this comparison, we'll say that the fuel economy for all three Ram powertrains hypothetically match the EPA's numbers. With four-wheel drive, the 3.6-liter and 5.7-liter gasoline engines are rated at 19 mpg combined and 15 mpg combined, respectively.

The current national average for diesel fuel is $2.61 and the national average for standard gasoline is $2.62. With those prices, here's what that fuel cost would be for each powertrain over 40,000 miles.

Ram 4WD 3.0-L Diesel V6: $4,745.45*
Ram 4WD 3.6-L V6: $5,515.78
Ram 4WD 5.7-L V8: $6,986.66

So the last thing here is to add our DEF costs ($213.99) to our diesel costs, which brings our long-term Ram's total to $4,959.54 ($4,854.02 if we'd bought all our DEF at the pump). I'll concede that there are several other factors at play here including tow ratings, upfront cost difference, maintenance and the (in)convenience of finding diesel fuel, but they just aren't big enough issues to scare me off this excellent powertrain.

Oh yeah, I ran out of windshield-washer fluid again. So I put in a gallon and it cost six bucks.

Travis Langness, Social Media Editor @ 36,363 miles

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