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Gas and Diesel Prices

Like a lot of you, I never thought I’d see a sign like this again.  Here in Salt Lake City anyway, gas can be had for under two dollars a gallon, and diesel for under three.  Seeing this got me wondering, what sort of effect does this have on the old Gas vs. Diesel motorhome debate?

And then there was our recent review of the Winnebago Travato.  With Winnebago offering a diesel option on the Travato, we have a very unique situation where you can get the exact same motorhome with either a gas or diesel power plant.  That’s probably as close as we’ll ever get to a true “apples to apples” comparison for Gas vs. Diesel.  Curiosity got the better of me, and I got to work with a spreadsheet.  I’ll make the spreadsheet available at the end of the post.  But I also created this quick-and-dirty breakeven calculator you can run right from this page.  Try it for yourself with your own assumptions.  It’s fun!

The Fit RV's Gas vs. Diesel Breakeven Calculator
Price per gallon of gas:
Gasoline Miles per Gallon:
Price per gallon of diesel:
Diesel Miles per Gallon:
Price per gallon of DEF:
DEF miles per gallon:
Extra cost for diesel engine:
Miles until Break Even:

I don’t mean to start a holy war with this post, and I’m not necessarily out to change anyone’s mind.  Heck, I don’t even know if I’m changing my own mind.  Nevertheless, the results of my little cost comparison are intriguing.  The cost savings from owning a diesel just aren’t as great as you might imagine.  Here’s a little snippet from the spreadsheet to get you excited (or angry).

GasvDiesel Result 1

That’s right.  With the assumptions I used here, the longer you own the diesel, the worse and worse the financial picture looks.  Here’s where I got my assumptions:

  • The price of gas and diesel is what you see in the picture, except I added 10 cents per gallon to account for mid-grade gas.  (In Utah, the lowest octane grade is 85. The Promaster requires 87.)
  • The mileage for the gas-powered Travato is the long term mileage posted from a popular 2014 Travato blog.
  • The mileage for the diesel ProMaster is frankly an estimate, but in line with what I’ve heard from both Winnebago and the ProMaster Forum.
  • Estimates for DEF mileage were all over the place.  I found some as low as 300 miles per gallon, and as high as 1250.  So I shot for the upper middle and used 1000.
  • DEF cost was from Amazon.
  • And the extra cost for the diesel engine was directly from Dodge’s “Build and Price” website.

You might argue some of these assumptions, but that’s why I’m giving you the spreadsheet.  The one assumption you could argue most easily is that the gas prices we’re seeing right now aren’t going to last.  So when you plug in more realistic recent prices for gas and diesel, you’ll find that you will break even with the diesel… EVENTUALLY.

GasvDiesel Result 2

Like, after 470,000 miles eventually.  Still not looking good for the diesel.  To put this into perspective: our own (non-DEF) diesel, Das Bus, was new in 2003.  This was 12 years ago, back when Lance Armstrong was still either winning or not winning Tours de France.  (Now there’s another holy war I want to steer clear of!)  Anyway, today, she’s got about 120,000 miles on her.  That’s just over one fourth of the way to making up the difference above!

Now being fair, this spreadsheet just looks at consumable costs, and the up front cost of the diesel.  There are a number of things I didn’t consider here that should still factor in to any “Gas vs. Diesel” decision.

  • Diesels generally retain much more of their resale value.
  • You’ll enjoy an extended range with the diesel.  If going 500 miles or more between fill-ups appeals to you, then this is something to consider.
  • A diesel motorhome might actually make it to 470,000 miles.  Gas… maybe?
  • Gas or Diesel – how many miles are you actually going to put on your motorhome?
  • Do you want diesel fuel on board for some other purpose? (Espar heater? A diesel generator?)
  • Maintenance costs and needs are likely to be different for gas and diesel motorhomes.
  • Is wondering “Does this station have diesel?” something you want to think about? (Not all of them do, and Stef and I have been annoyingly burned by this on more than one occasion.)

And there are probably more than that. Even so, when I actually sat down and did the math, I was surprised at how the numbers turned out.  I’m not yet ready to completely give up my diesel snobbery.  But after going through this exercise, I’m having more of an open mind about the Gas vs. Diesel question.  And please remember, I’m just presenting information for you.  I’m not necessarily trying to tell you that you need one or the other – that will depend on your individual circumstances and preferences.

And now, about the spreadsheet.  You should be able to just change the assumptions in the top part and watch things change.  In addition to the break even mileage in yellow, there’s also an operating costs chart, and a graph in case you want to see things presented those ways.  With some of the assumptions from above, the chart looks like this:

GasvDiesel Operating CostsAnd the graph looks like this:

GasvDiesel Operating Costs Graph

I’ve protected the formulas to keep you from accidentally changing anything, but there’s no password on the sheet – if it asks you for one, just hit enter.

Gas V Diesel

I can’t decide if I’m curious about or fearful of the comments you might leave, but feel free to do so anyway down below!