Another Gas vs Diesel Comparison

[RVcyclist]

I had hip resurfacing surgery on December 3rd and am stuck at home while I am recovering.  Since I have a lot of spare time I have been reading the forum regularly and spending a lot of time on the internet looking at motor homes.  I am strongly considering upgrading from a 10 year old class C to a newer (2005 - 2007) class A.  Until recently I was only considering gas coaches because I have some tight turns to make to get to my house and maneuverability is a concern.  I have been looking mostly at gas units in the 28' - 32' range; however, I recently found a couple of 33' diesel pushers that look like good alternatives.  And, the prices of the diesels are attractive.

Since I live in the North Carolina mountains, I think the diesel will give a significant advantage on the steep grades I frequently encounter (I am disappointed in how much trouble my class C has when towing my boat up some of the grades). 

I have read several of the past discussions on the fuel costs for gas versus diesel, and I decided to do a little analysis of my own.  The analysis is summarized in the attached file.  I was curious about the fuel costs differences for gas versus diesel, so the first thing that I did was download fuel cost data for the first week of each month of 2008.  Then I calculated the fuel cost per mile for diesel assuming 9.5 MPG and the fuel cost per mile for gas assuming 7.5 MPG (these values are loosely based on MPG values that I have observed in various discussions).  These costs for each month are given in the table.

The last column gives the "Breakeven Diesel MPG."  This is the MPG that a diesel coach would need to achieve to have a fuel cost that is equivalent to the fuel cost per mile for a gas coach with 7.5 MPG fuel consumption.  Based on this analysis, when fuel prices were higher earlier in the year, the diesel coach would only need to achieve 1 to 1.5 MPG more than the gas coach to breakeven with the fuel cost for the gas coach.  However, as fuel prices dropped over the past couple of months, the difference in the price of diesel versus gas has increased.  Therefore, for November the breakeven MPG for the diesel is 9.9 MPG (2.4 MPG higher than gas) and for December the breakeven MPG for the diesel is 11 MPG (3.5 MPG higher than gas).

If the difference between the cost of gas and diesel stays as high as it was during the first week of December and if fuel prices stay low, diesels will have higher fuel costs than gas unless the diesels can get at least 3.5 MPG better than gas coaches (again assume that the gas coaches get 7.5 MPG).  Is it likely that a diesel will do that much better than a gas coach?

My opinion regarding fuel prices is that they will remain close to the current level for much of 2009 and then start increasing as economies around the globe start to recover.  I do not have a strong opinion regarding what will happen with the difference between the cost of diesel and the cost of gas.  My gut feel is that, in the long run, diesels will be the better option when considering only fuel consumption (ignoring the cost differential for diesel coaches vs. gas coaches and the higher maintenance costs for diesels).

I did this analysis in hope of getting a better idea of which coach to buy.  The diesels that I have found cost more than the gas units that I have been considering; however, I am leaning toward the diesel because of the hill climbing ability.  In addition, the diesels are higher-end coaches, so it is an apples to oranges comparison.

Hopefully in a couple of weeks I will be recovered enough from my surgery to go start looking at the coaches in person (most of the coaches that I am looking at online are 3 to 5 hours from my house).

Questions and comments about my analysis are welcome.  Also, any comments that may help me make a purchase decision are welcome.

Delbert

 

[rankjo]

Gas/Diesel mileage is only the starter.
I drive a gasser because I understand gas vehicles, and they are cheap to maintain.  In fact, I do the oil and lube myself,  (saving a little but avoiding going to the dealer), and since in Canada I have to have an annual inspection anyway, which includes examination of the rear brake pads on at least one wheel, and the front discs, I feel reasonably safe.

My personal view of diesels is that they cost more to maintain.  All those air systems, (about which I understand nothing), and the idea that most diesel owners don't change their own oil or lube them selves.  Also, I think that hydraulic brakes are simpler then air brakes, (and I may be wrong about that).

Owning a gasser is very simple, and any garage in town can look after it. Bring a big diesel to a garage and they take fright.  JMHO.

Rankjo

 

[mphy98]

depends upon use. diesel has more torque, a few if any miles to gallon advantage.  but the repair costs are 10 times that of gas, and maintence cost double at least.  if your going to tow then diesel is best, just a few uses a year no towing, then you will never break even between the cost in my humble opinion

 

[rayincorrales]

I have wrestled with this analysis too, at the moment I am considering an upgrade too...I have several friends who have diesels (I have a gas Fleetwood) and what I've been told is that the diesels will likely not get any better MPG due to the increased coach weight of the diesel, however there is no doubt that the diesel will climb hills and tow WAY better than the gas units. Another issue is that without driver constraint, you may find yourself driving faster in a diesel because you can, thus no savings in mileage.

On a recent trip here in New Mexico, I compared notes with one of my diesel friends and on the same trip, I averaged 8MPG in my 35' gas and she averaged 6.5MPG in her 36' diesel. However, she absolutely blew by me on a steep grade where I was struggling to maintain 50MPH. I would guess that she was easily doing 60+MPH.

Another diesel friend told me once, "if you don't want to buy a diesel then never drive one", his point was that the ride of the diesel's was far superior due to the beefed up chassis and frame, he also claimed that "the security" of driving a diesel is unmatched.

All of this is opinion and not scientific, but I know what you are struggling with...

Good luck.

Ray

 

[seilerbird]

After almost 5 months of shopping me and my girlfriend just bought a 2006 Fleetwood Providence 39L diesel pusher. Early on I wanted a DP and GF wanted a gas. I almost had to force her into test driving a DP. It took her about 2 minutes to fall in love with it and it was hard getting her out of the drivers seat. Here is what I discovered about the gas vs diesel controversy.

Diesels get better mileage but gas is cheaper. It ends up a wash.

Diesels cost more the service but need fewer repairs. Ends up a wash.

Diesels cost more initially but last much longer, ends up a wash.

So from what I gather in the long haul it is a wash. It is simply not possible to computer gas mileage costs as you have done. When I first started looking in July diesel was over $5 a gallon and gas was $3.99. Today I paid $1.91 and gas at that station was $1.59.

The guy who said if you don't want a diesel then don't drive one hit the nail on the head. There is no comparing driving a gas to a diesel. I haven't had mine up a really steep hill yet, but the moderately steep hills I have been up don't faze the engine at all. Flatten out the hills and makes them like level ground. The turning radius on a diesel is mind blowing. You talked about having tight turns to negotiate then get a diesel. Riding down the highway is like floating on a cloud. Having the engine in the rear is wonderful. Almost no engine noise or vibration. Just that point alone makes them worth the purchase.

BTW - I just completed a Texas to Las Vegas 1200 mile trip and we were getting 9 mpg all the way. We were not towing and we drive about 55-60 miles per hour. Weight has almost nothing to do with gas mileage. Your heavy right foot has a whole bunch to do with it.

 

[Mark R.]

Delbert nice job on the gas Vs diesel chart, that said you have waaaaaaaaaaaay too much time on your hands! I agree with most of what I read above from others, in NY where I live gas is at 1.83 diesel 2.86, I have a diesel pusher and yes the power is nice but the real nice part is the motor is 34 feet away from you so you can hardly hear it. Some years ago you could buy a GAS PUSHER, if the diesel price stays high maybe someone will build them again. They can build big powerful gas engines, all you need is a market! Hope you get well fast, good luck shopping for your new rig.

 

[Jeff]

Delbert:

We enjoy our Cat powered/Freightliner chassis Tradewinds a great deal. We are full timers and it does provide distinct advantages over the gas m/h's available four years ago: a better ride, more net weight carrying capability, more storage room in the bays, and an exhaust brake for coming down the grades. (Going up was never that big a deal with our Banks-powered 460 Ford in a 37' Pace Arrow.) Today's new gas chassis choices answer most of the weight issues and have adapted transmission brakes for the descents.

The price of all this is operating costs. While fuel evens out (higher price but better mileage for the Cat) I was able to do much more of the maintenance on the Ford (Almost all) and when something does break on the Cat or Freightliner it is expensive!

I am not against diesel power, just suggesting there still is no free lunch. ;D

 

[RVcyclist]

Thank you all for your input.  Mark, I definitely have waaaaay too much time on my hands, but I like doing financial analysis in Excel (I am a finance professor) and it was interesting to see how the numbers add up.

Over the next two or three years our travel will be restricted due to having two teenage sons in school.  During this period the diesel will not be practical.  Over the long run, we expect to do a lot more traveling as we will have more free time to travel.  So, in the long run the diesel may be practical.

The diesel coaches that I am considering are 33' National Tropi-Cal (orphans) on Freightliner chassis.  Am I correct that the Tropi-Cal is a higher end coach?  I know it is not top of the line, but can you give me an indication of where it lies on the spectrum (entry-level on one end, top of the line coaches on the other end)?  The gas coaches that I have been considering are more entry-level.  Can you give me some examples of gas coaches that are comparable to the Tropi-Cal in terms of quality, equipment, accoutrements, etc.?  This will help be better judge the value of the Tropi-Cals and will be beneficial in my decision making process.

Thanks again, Delbert

 

[Gary RV_Wizard]

Some years ago you could buy a GAS PUSHER, if the diesel price stays high maybe someone will build them again.

Workhorse already builds a gas pusher chassis called the UFO. The Winnebago Destination and Itasca Latitude are built on it  as standard (the Freightliner diesel chassis is an option on those models).  It 's abut the only model where you can make an apples-to-apples comparison of gas vs diesel in  the same motorhome.  However, the Freightliner diesel adds air suspension and brakes as well  as the diesel power, so its still not quite the same.

The Tiffin Allegro is available as a front diesel (FRED) or gas model, so there is another opportunity to compare. The FRED chassis has spring suspension and hydraulic brakes and a 24,000 lb gvwr, so is essentially identical to a gasser of similar size/gvwr except for the engine itself. Take a look at the Allegro Brochure on the automotive specs page and you can compare.  This coach  delivers about 10.5 mpg in FRED diesel form and around 8.0-8.5 mpg in gas form. 

Diesels cost more the service but need fewer repairs. Ends up a wash.

Modern engines require so few mechanical repairs that I don't see this as a factor unless you drive a coach 200k miles or more. Even then I'm not sure, since cracked heads or exhaust manifolds seems to be a fairly common malady in RV diesels, just like it is in RV gas engines.

 

[seilerbird]

"Modern engines require so few mechanical repairs that I don't see this as a factor unless you drive a coach 200k miles or more. Even then I'm not sure, since cracked heads or exhaust manifolds seems to be a fairly common malady in RV diesels, just like it is in RV gas engines."

You are correct, Gary. I was thinking mainly about oil changes and routine service. But most of what I am saying comes from what I have read on this and other forums from people with more experience then myself. But since this is the motorhome that we are retiring to I just may end up putting 200k on this puppy. I hope I live long enough to do so.

 

[Gary RV_Wizard]

Diesel service (routine maintenance) is definitely a lot more expensive than on a gas engine.  They have more filters that are more expensive and greater volumes of fluids to change. Diesels even have coolant filters that gas engines generally do not employ.

The complex air suspension and brake system also  seems to need fairly frequent repair (leaks).

 

[Mark R.]

Thx Gary I had no idea that someone was building a gas pusher, I will have to read up on it, I wonder what their owners think of them?

 

[Mark R.]

Did a little reading and found the following owner comments about their gas pushers, sorta what I expected.

Robert :  This is my 6th RV. The UFO is fantastic and my all time favorite-gas is the way when in the rear.You cannot hear the engine. Have done alot of mountain passes towing a Honda Fit, 2,600 lbs. Do not know the car is there. I have had ZERO problems. ZERO, I am in shock. Winnebago got it right and I salute them. WOW what a ride. My mileage in the mountains towingis 7.4. The stereo system is mind blowing. The design of the interior modern and anti-old Winnebago boring.Somebody at W should get a big raise for desigining this plush fun coach.

AB :  Hi: Test drove one of these today(Itasca Destination) beautiful coach inside. Handles like a dream, can't even hear the motor. Functional coach, think I'll be buying it on Monday!

Ronnie Cotes :  I would like to see a comparison between the gas and diesel prices. I think this is a breakthrough coach, I like the idea of being able to choose diesel or gas, especially with the gas engine being in the rear. I've had 2 class A motorhomes and both were gas. Both had the big disadvantage of the noisy engine at the front with the big bulge between the front seats.

 

[Kirk]

No doubt about it that a diesel rig has advantages over the gas rigs, but they won't save you money. Very few RV owners keep one even close to long enough for the longer life of the diesel to begin to offset the original cost.

In gas, it is true that Workhorse has some interesting innovations, but they have also had many problems unique to their product and have far fewer service locations than do the Ford chassis. Not sure which I would buy if I were buying new today, but if you buy a gas RV, check them both since each has it's own advantages.

If you want the best ride and handling, get a diesel with air ride. They frequently have more cargo capacity and nearly always more and better storage. The key is, for your budget is the extra cost worth it for the advantages?

 

[Just Lou]

Well said Kirk,

The differences between gassers and DPs are many, and in some cases very significant.  The question a buyer has to ask, and ultimately answer, is;  Which is Best for me?

My selection process was pretty simple and I've never second guessed it.  Being chronologically challenged (70) and possessing limited discretionary funds made a used gasser BEST for me.

 

[RVcyclist]

Thanks to all for the input.  I am leaning toward the diesel, but not because I think it will save money.  I expect the operating costs to be more than a gas; however, I hope the benefits of a better ride and more power will offset the higher costs.  Given that I live in the mountains, every trip requires some steep grades.  For most trips I will be towing a boat or a toad, so the power will be nice. 

I am a pretty conservative driver and when traveling with the RV I hope that I am not in a hurry (being in a hurry takes the "recreation" out of recreation vehicle).  I hope that a 33' diesel driven conservatively will get pretty good fuel mileage.  I hope the fuel savings will help offset the maintenance costs.  But, based on my analysis, if the difference in the cost of diesel fuel and gasoline does not narrow, that will not be the case because there will not be any incremental fuel costs savings with the diesel.

Another factor in my decision is the initial cost.  The used diesel coach that I am considering cost about $15,000 more than the gas coaches that I have been considering, but the gas coaches are entry-level units and the the diesel appears to be a mid-level coach.  So, part of the higher cost is justified by the coach and not strictly due to the diesel chassis.  In my on-line search I have not found any gas coaches that appear to comparable in terms of size and equipment.  Long-term I think that we will be happier with diesel coach and less likely to want to trade-up in a few years.  My wife and I are in our late 40's and I hope we have many good RVing years ahead of us.

Having said all of that, I still have not driven any of the coaches.  I go back to see the Dr. on Monday and I hope that he will release me to drive and let me transition from the walker to a cane.  Then I can start taking test drives and maybe make a decision.  The decision may be to keep the old class C for a few more years.

Again, thanks for the input.  Please keep the comments coming; this has been very helpful.

Delbert

 

[Gary RV_Wizard]

Diesel fuel contains about 10% more energy than gasoline. On top of that, diesels run at higher compression ratios and are more thermally efficient than gas engines. All this combines to yield 15-20% more miles per gallon of fuel with diesel vs gas.  And if the gas is an ethanol blend, it gets even better (ethanol has less energy than gasoline, so ethanol blends get lower mpg than pure gasoline).

So if the diesel prices exceed gas prices by 20% or more, you don't have a prayer of coming out ahead on fuel economy.