Originally Posted by jerztime
Greetings all! Trying to choose our first RV and would love input on gas vs. diesel. The plan is to get a 25-ish foot motorhome and at some point tow a small car (think Mini-Cooper). Am interested in insight on power, maintenance, any insight you can offer. Many Thanks!!!
A big problem with the RV industry is fuel economy. Many Otto engines (actually the automotive gasoline engine is Daimler/Maybach's, not Otto's) used for RVs have very poor fuel economy with 6 to 8 mpg being a norm. Today's atmosphere can see one international incident raise prices by $1.00 almost in hours.
The Diesel engine is typically 30% more efficient, but in many older engines, is extremely dirty producing high levels of carcinogenic exhaust fumes. Gasoline exhaust fumes are also as poisonous as older Diesels and the fuel (benzene) is carcinogenic. Modern Blue-Tech (and other Common Rail Diesels such as Cummins) burn clean and have odor free exhaust (like Cruise Ships) and lack the loud Diesel Knock of older truck engines.
Modern engine designs have cleaned up Diesel exhaust. Gasoline engines have lost a lot of efficiency by being made to run more cleanly while Diesels have improved greatly.
Gasoline engines have low hp output over much of their range while the hp output of Diesel engines is typically higher over their rpm range. So a typical 350 hp gasoline engine may produce only about 50 hp during much of it's rpm range while a lower hp rated Diesel, running at lower RPM may produce the same, but typically MORE power. The 188 HP Mercedes-Benz Diesel in the Sprinter chassis actually performs more like a 250 hp gasoline engine while using far less fuel and less pollution in 3 of the 5 polluting gases.
So the Diesel power curve is ideally suited to heavy duty use when constant loads are heavy (such as pulling a motorhome, locomotive, ship etc.) where gasoline engines have to be sized MUCH larger to achieve the same pull and performance. The MB Diesel is a heavy duty truck engine while I believe that many of the gasoline engines used in RV chassis are medium duty. Ergo, the Diesel is higher priced.
Because gasoline will burn only in a narrow range of stoichiometric mix rations from about 8:1 (8 to 1) to 12:1, this raises fuel consumption at idle and at low throttle compared to a Diesel which can run as low a 200:1.
So the Diesel is a far better engine in principle from the start. In the Sprinter the MB Diesel is a Heavy Duty engine with a life span of considerable length. The typical gasoline engine used in medium duty trucks is not nearly so durable. I doubt this matters because I don't believe the typical motorhome's body will last long enough to recover on this investment.l
The MB Diesel also meets all current pollution standards. Newer gasoline engines found in trucks do also, but not all diesels found in the marketplace do. If the engine produces the old acrid diesel exhaust odor, then it's either damaged or the old poisonous design.
You do pay quite a price for an MB Diesel. If you drive 10000 miles, based on today's fuel prices with 10mpg for gasoline ($3.45) and 15 for the Diesel fuel ($3.89) for the Diesel will be $850 cheaper for fuel.
Many gasoline engined motorhomes get 6 to 8mpg. (At 6 mpg for a typical Class C then the advantage at 10K miles for the Diesel rises to $3100.) At tune up time, the Diesel will not require spark plugs, but will require a decent fuel filter and Blue-techs use DEF fluid every few thousands of miles.
Diesel fuel, worse that gasoline, needs to be stabilized if left sitting in a tank as it grows algae in it. But gasoline sublimates and forms shellac if not similarly treated.
Diesel injection pumps are destroyed by the presence of water. Gasoline engines typically just stop running. Diesel fuel filters will cut off the fuel flow entirely in the presence of water and cost more.
Based on my survey of 25' Motorhomes using both gasoline and Diesel engines I find the price difference to be about $20,000. If you have one of those 6 mpg Motorhomes then you'll break even on the price of fuel alone in about 42 months.
But, this on only PART of what I considered when I purchased my Sprinter Diesel chassis in a Itasca Navion IQ. The handling and quality of the chassis should be considered. Not all motorhomes handle like the large van that the Sprinter is. It steers very easily and accelerates far faster than you might expect for a 10,000 lbs vehicle with a 3 liter engine. On the highway I get about 17 mpg (15 in the mountains).
I used to drive a 225 cu. in. (3.7L) gasoline Ford Truck which weighed about 4400 lbs and it couldn't get out of it's own way. I didn't weigh enough to be able to push the brake pedal hard enough to lock the wheels, even though I pulled up on the steering wheel with about 75 lbs of force while pushing on the pedal with both feet. My Sprinter requires a lot more pressure than my cars, but is reasonable.
There is a good reason that some writers refer to the Mercedes Sprinter as the "savior" of the RV industry and it's not just fuel economy. It's also the quality of the chassis and all it's ancillary systems, like ABS (Anti Bockier System) anti-lock brakes, and it's excellent handling.
Almost all Class C (and some Class A) makers today seem to have a Sprinter based unit, and they are selling very well. There are also class A Sprinters which are also about 25' long and get from 16 to 18 mpg.
As more and more people grow tired of the size problems with larger units they tend to settle on the 25' long Sprinter based units and are not disappointed. Not to mention that many RV parks do not have spaces longer than 30' or pull though sites.
The Sprinter has a 54 foot turning circle. This is a major advantage compared to many other RVs. I was easily able to make a turn in Gettysburg where a Class C gasser (about 28 feet) could not.
Diesels burn their fuel with an excess of air. This results in their having better performance at higher altitude. I spent last weekend at 2700-2800 feet. I was blowing past gasoline Class C RVs as if they had the anchor out at that altitude going up long inclines. I have heard from others in forums that the gasoline engines lose a great deal at higher altitudes.
So far, all these considerations tend to feel like personal opinion and a choice could still go to gasoline (the explosion engine) or to Diesel. The factor that I tend to go with is the same factor that leads me to tend to buy features in automobiles and homes that I personally don't care about.
That factor is resaleability. You may pay $20,000 more for a Diesel RV (any of them not just the Sprinter) but you will tend to:
A. Be able to sell your unit more easily.
B. Recover a higher percentage of the purchase price (lower depreciation).
C. Have longer and less expensive regular service. (Class C not large DPs)
We (automobile people) used to say the cheapest car to own was a Ferrari (or Rolls-Royce or Bentley or other exotic car) because you can resell them for as much or more than their original prices in many cases. Diesels tend to be cheaper to own.
Of course if you cannot afford the extra money up front, this is a moot point.Most of the automobile manufacturers are phasing out the old oversized engines of the past (GM is lagging behind). They are being replaced with smaller turbo supercharged engines that are more efficient.
If you want to check out the Leisure Travel Unity series with the MB Sprinter 2.1 Liter Diesel, it is using the latest Sprinter with 7 speed transmission. It also has many of the options than Winnebago seems to not yet mention in their preliminary advertising for their 2015 models.
My choice is for a Diesel Sprinter based RV. You should chose based on what you feel is most important to you, not due to other's (like my) opinions.
Simply comparing Diesel to the Gasoline engines is not a granular enough comparison to make a well informed decision. I looked at the actual RVs and how well they were executed and how well they perform on the road as well as all the factors I mentioned above.