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The information provided in all "Your RV" pages are only suggestions and anecdotal stories.  The information in these pages is a generic peace of work and is meant only as a general guide, it should not be taken as absolute fact. The information provided in these pages can change at any given day.  Please read our RV Manual page for more information.

Today all motor homes have many alluring features, living comfort, power, torque, slide-outs, basement storage, riding and driving comfort, fancy graphics and yes–prestige. There is a wide array of products to choose from for the first time owner or those considering an upgrade.

They all share several common features, such roof air conditioners, hot water heaters, furnaces, kitchen stoves, refrigerators, and slide outs. Motor homes have become more luxurious and more sophisticated in the last few years and of course with these enhancements the prices have gone up; so have the weights. To bridge the price gap between gas and diesels rigs, several new "entry level" diesel models have made their appearance. Their prices are only 20 to 30% more than the high-end gas motor homes. This has led to a marked increase in diesel powered motor homes.

So the question presents itself to the existing gas motor home owner or to the first time buyer: Should I spend more money and buy a diesel pusher?" What follows is an attempt to give buyers some food for thought in the deliberation of this question. Lets compare the fundamental parameters between today’s gas powered motor homes vs. their diesel counterparts. (This discussion will be limited to class A Motor Homes in the range of 32 feet to 40 feet in length.)

Engines

Herein lies the most distinguishing factor between the two types of motorhome. The gas power train will consist of a V 10, Ford or a V8, Chevy. These power plants were developed for the light duty trucks. The horsepower rating of the V 10 has just been boosted to 310 hp, 6.8 liter with 420 ft./lbs. of torque. The V8 offers 290 hp, 7.4 liter with 410 ft./lbs. of torque. The gas hp ratings are "peak" and our only delivered at relatively high RPMs of 3600 to 4200. The diesel offerings are 300hp, 8.3 liter with 860 ft./lbs. of torque, 330 hp, 8.3 liter with 950 ft./lbs. of torque and 350 hp, 8.3 liter with 1050 ft./lbs. of torque; these are all the same Cummins (ISC) engine with different fuel management programs. The diesel hp ratings are delivered at 2250 RPM. Caterpillar offers their 3126B family in this range, with power ratings of either 300 hp or 330 hp. This class of engine was developed for RVs, delivery trucks, transit-mix trucks and school buses. Even larger diesel power plants with ratings of 400 to 500 hp are also available on a few coaches. Cummins also makes the very popular entry-level ISB 275 engine. It is a small (5.9-liter) engine, with a rating of 275-hp (2600 RPM) and 660 ft./lbs. of torque. A companion version is also now being offered with 260-hp, 550 ft./lb. These smaller engines are all applied to lighter entry level diesel pushers.

Diesel engines provide power and torque that a gas owner can only dream about! Even the small 5.9-liter diesel will run off and leave a gas rig in hilly or mountain terrain. Torque is good, more of it is better; it is the force that causes something to move or go into motion. Diesel engines supply more torque than equivalent displacement gas engines and they deliver their peak torque and peak horsepower at much lower RPMs. This results in less piston travel and engine crank rotations over a given distance. The direct result is less wear on engine components. This is why a diesel engine has a life expectancy that is considerably longer than a gas engine; their longer warranties reflect that fact. You won’t see any commercial cross-country trucks with gas power plants; even the light intra city haulers are usually diesels.

Another big plus for diesel power is the fact these turbo inducted units do not lose any of their power in the mountains. Gas engines typically lose 3 % of their power for each 1000-ft. of elevation. (Cummins power ratings are based on sea level to 7,000 ft. with no degradation. The diesel power plant is the big winner based on its ability to deliver higher horsepower and more torque plus a much longer service life as opposed to the gas engine.

Transmissions

The gas motorhomes are coupled to, light truck, 4 speed transmissions. The bigger, heavier diesels are all mated to the industry standard, the Allison 6 speed World Transmission with few exceptions. (Some low cost entry-level diesels offer the smaller 4 or 5 speed Allison transmission.) The 6-speed transmission is very rugged, and sophisticated. A powerful computer controller adapts its shifting program to the driver’s style and demands. It is a true truck transmission. The shifting experience and power transfer with one of these transmissions has to be experienced. The electronic shift control of the 6 close ratio gears, along with very timely converter lock-ups make for a very smooth and "seamless" operation! The gas engine’s transmission struggles because the ratio between the 4 gears is very wide. This is really evident when you have to start from a standing stop at the bottom of any kind of incline. The diesel power train wins hands down, with the higher horsepower, higher torque, and 6 forward speeds.

Chassis

Before 1999 it was very easy to overload a gas-powered motorhome. This was the year that one manufacture, (Ford), increased their Gross Vehicle Weight Ratings (GVWR) by 3,500 lbs. This gives gas buyers a 20,500-pound GVWR. Diesel-powered chassis’ offer GVWRs of 24,000 to 36,000 lbs. Chassis lengths in gas rigs top out at 208 or 228 inches, beyond that they resort to the use of a tag axle. Diesel chassis’ extend up to 278 inches, with out a tag axle to supply 40 foot hull lengths. Some gas chassis’ extend 13.5 feet beyond the drive axle; this creates a very significant "tail swing" when turning. The gas chassis’ are certainly adequate for most motorhome applications, however they do not begin to offer the quality of ride, steering control, nor the stability that is typically found in a diesel pusher. In a crosswind a gas rig driver will constantly be required to make steering wheel adjustments to maintain course; this is referred to as "bump steering". It can be very tiring in the course of a day’s driving under such conditions. (The entry-level diesels will also exhibit this characteristic to a lesser degree.) The heavier diesel rigs with "active" air bag suspension can typically be driven with one hand on the steering wheel, even in the presence of a crosswind. They are much stronger and they of course are much heavier. They have to be sturdier because they are supporting a very heavy power train and large payload capacity, compared with the typical gas powered unit. (An 8.3-liter diesel engine weighs 1530 lbs. while it’s Allision transmission weighs 535 lbs.). The gas V10 engine weighs around 525 lbs. while it’s transmission weighs in the area of 300 lbs. One subtle advantage of the diesel pusher with it’s rear engine is the fact the entry door can be placed up front or mid-ship; this provides a more flexible floor plan that has no engine "dog house" in the front. The diesel chassis wins based on driving stability, floor plan, quietness of operation, and comfort through out a day of driving. They produce less fatigue for driver and co-pilot; this yields more enjoyment.

The Hull

The hulls or bodies of motor homes are all very similar. They all contain fiberglass exterior walls with aluminum or steel frames in the walls and roofs. Polystyrene foam board material is used for installation. The interior walls are covered with Luan and the ceilings and roofs utilize a combination of plywood and Luan. The wall construction will typically be done with vacuum bonding; Gel-Cote will cover the exterior walls. The graphics designs on the exterior of a gas rig will usually be accomplished with decals, whereas the diesel product will have those graphics spray painted on. Decals have a limited life when exposed to the elements. The roof of the gas motorhome will be rubber sheet (EPDM); it costs less than the fiberglass roof coverings found on most diesels. Rubber roofs are harder to keep clean and tree branches can tear them. The diesel product will usually have fancier interiors with cabinet quality that is generally superior to that found in the gas product. Gas rigs are not generally offered in lengths of over 36 feet (and that is literally stretching it–with a tag axle). Diesels with lengths of 36, 38 and 40 are the norm. Shorter, 32 and 34 foot, diesels are available They offer a great power to weight ratio and they can go where many of the large rigs can't. If you are a full timer or extended traveler and you can afford one–the diesel pusher is highly desirable.

Capacities

These numbers are important to anyone who is going to "full time" or do extended travel in a motorhome. Gas models offer a 75-gallon fuel tank; diesels offer fuel tanks of either 90, 100 or even up to 150-gallon capacities. This provides the diesel owner with considerably greater driving range between fuel stops. You will find larger capacities in the liquid tanks in a diesel. Storage capacity is generally bigger in a diesel vs. a comparable length gas unit. The diesel motor home has a definite advantage in all carrying capacities.

Brakes

The gas offerings have hydraulic disc brakes with ABS. The diesels have air activated drum brakes with ABS. However, at least two diesel pusher manufacturers offer very powerful hydraulic disc brakes with ABS. It is claimed that their braking efficiency is equal to or better than the conventional air brakes. It is generally an accepted fact that diesel motor homes have superior braking systems compared to those of gas powered motorhomes. Today, all diesels come equipped with an exhaust brake retarder to help them ease down grades; gas units lack this devise. A superior braking system is one of the major strengths that diesels have over gas powered units.

Please read our Brakes page for more information.

Tires and Wheels

Gas rigs come equipped with 19.5-inch wheels and low profile tires; the 16-inch wheel is history. Diesel rigs come equipped with 22.5 inch wheels and tires which may be of the low profile G 159 type or the large conventional truck tires that are either 250mm, 275mm or even 295mm in size. Whether gas or diesel powered, one needs to be assured that the tire load ratings are proper and have plenty of weight margin in their capacity. Large wheels and large tires help nullify the effects of road feedback; they generally provide a better ride–assuming a decent suspension exists. Advantage diesel.

Please read our Tires page for more information.

Service Costs

There can be no doubt that it is more expensive to service and maintain a diesel powered motor home. The oil changes and filters, diesel typically-24 quarts versus gas-6 quarts, plus the diesel’s large fuel and air filters will definitely cost the diesel owner a lot more. However Cummins has increased the oil service interval to 15,000 miles. The heavier maintenance requirements for braking systems and the cost of tires will also exceed the gas motor home service expenses. The diesel owner will never make up the difference based on the somewhat better fuel mileage that a diesel produces. The advantage, here, lies with the gas-powered motorhome.

Cost

Finally there is the matter of price and affordability. If price was not an objective, I suspect that almost everyone who wanted to own a motorhome would buy a diesel pusher. One must answer the question: "Is it worth it?" To many who can afford a diesel, the answer is a resounding YES! The reasons are compelling and the value is there for those who can see it. You may ask the question: "can I have fun and enjoy RVing in a gas rig"? Absolutely, they all can offer a lot of pleasure. And the manufacturers are making our choices a lot easier by offering so many entry-level models in gas and diesel. There is a suitable model out there for everyone.