Choosing Gasoline or Diesel Powered?

[JohnnyT]

I realize that this is a long thread but if you are pondering the Gasoline versus a Diesel based on power consideration or are wondering about adding an after market performance enhancing kit to a Gasoline engine to close the power equation it might be worth a read. This thread is intended to be an addendum to the First Time Buyer... sticky.

The question of a Gasoline versus Diesel is a topic that seems to have no correct answer. But one that comes up frequently Here is some food for thought, after you have done some looking post questions about specifics and you will get plenty of feedback.

Diesel can have more torque and HP but that does not always translate to better performance and higher MPG. There are some configurations of Gasoline powered Motorhomes that will out perform some Diesel coaches due to weight to power ratio, gearing, rear axle ratio. There are some diesel powered configuration where power is not an issue with any grade or load.

In terms of reliability Diesel engines are constructed to have a longer life span but for most folks and I mean most, the reliability and longevity is sort of a non issue due to the amount of mileage and the length of ownership. Diesel's will be somewhat more costly to maintain.

The longer and heavier a coach is the more need there is for power. There is also the issue of carrying capability. So you will want to focus in on what size motorhome then look at the weight carrying abilities of your choices.

The modern Gasoline power trains and chassis have evolved tremendously in the past several years and the expectation that they will continue. If there is a Gasoline powered motorhome that meets your fancy it is worth a long hard look.

There are some benefits to going diesel powered other than fuel mileage ( which is not usually anything to write home about) A DP pusher will generally be quieter in the cockpit area when underway and will have the benefit of air suspension and Brakes.

Another minor benefit of a DP is that in many cases A DP will have a much longer range between fuel stops due to the size of the fuel tanks.

If you are looking at a length of the 35 or less then I would be looking at A Gasoline and over that you are in sort of a mixed bag up to about 38 feet then you really want to be leaning in the direction of a Diesel simply because of the torque to handle the weight.

You will need to sort out what you are looking for in terms of length and CCC plus the price range you are wanting to be at. A diesel will be a significant increase in price. Drive both and then figure out if the added cost is worth it to you.

So what does this all mean?

Some gasoline powered coaches will be challenged going up some steep or long grades but then so will some diesel powered coaches. The real question is so what? How much time will one spend going up steep grades?

There are aftermarket kits that can enhance performance such as the Banks System or the gear Vendors add on to the none Allison transmissions that adds extra gears. The Banks after market performance enhancements are available for both Gasoline and Diesel powered units. I have installed both in the past and still have a F350 4x4 that has both the Banks system and the Gear Vendors. The addition of a Banks or a competitive alternative will yield additional available power both in terms of Horsepower and Torque. The question of whether the additional cost of these systems will yield enough performance enhancement of warrant the cost.

In looking at the performance curves relative to the 8.1 on the Banks web site it should be noted that for an 8.1 the optimum gain is at a fairly high RPM which should be taken into account relative to cockpit noise. Using the most optimistic gain estimates you could be looking of 16 to 23% depending on rpm's in terms of torque. The RPM range will be between 3800 and 4800. The most material gain will be on acceleration especially on on ramps and passing.

In terms of pulling power up grades there will be improvement there as well. But lets compare getting 25,000 pounds up a grade with a banks enhanced gasoline 8.1 with getting 30,000 pounds up the grade with a Cat 330 powered diesel. Looking at the chart below the 8.1 with the Banks system will have to move 45 pounds for every foot pound of torque versus the Cat which will have to move 35 pounds for every foot pound even at the heavier weight. You can also see on the chart below that at the same weight the diesel will have even a greater advantage. However that is not the end of the story.

The W24 chassis comes with a 5.86 rear ratio which is nominally in the range of 20% higher than the typical rear ratio of a cat 330 equipped chassis so the 29 percent more weight per foot pound of torque available with the cat 330 is down to about a 9 percent difference in power to move the weight provided the gasoline unit is 5,000 pounds lighter. If the same weight then the cat will have about a 25% advantage in the ratio of weight to torque to move it even with the performance enhancement on the Gasoline engine. How much difference will this make to you? The only way to answer is to drive the same course with the two different power trains and see for your self.

Keep in mind that you will more than likely be testing a stock Gasoline engine and that adding a Banks or similar performance enhancing package will yield somewhere in the neighborhood of a 20 % improvement. What this means is that the performance enhancement kit will offset the weight that you are going down the road with towing a dinghy and with all your stuff on board. So if the performance suits you and you like the rest of the coach the Gasoline powered motorhome ought to be on your short list since it is possible to add the performance enhancement kit. The added expense of a performance enhancement kit will be far less that going the diesel route. The diesel as tested will be just about as good as it will be so keep in mind that the added wieght of towing a dinghy and carrying all your stuff may impact the performance you experienced during the test drive without the additional weight.




Torque.........455.. 560... ..660.....860.. 1050.. 1200

Weight
20,000......... 44... 36........30........23......19......17
25,000......... 55... 45........38........29......24......21
30,000......... 66... 54........45........35......29......25
35,000......... 77... 63........53........41......33......29
40,000......... 88... 71........61........47......38......33
Pounds to move per increment of torque

455 = Stock 8.1 Torque
560 = Banks equipped 8.1 Torque
660 = Cummins ISB 300 Torque
860 = Cat 330 Torque
1050 = Cummins ISC 350 Torque
1200 = Cummins ISL400 Torque

So the answer is yes these after market systems will help off set the power differential between a Gasoline Powered versus a Diesel Powered unit.The difference in actual performance getting that weight up the grade while not be as much as the chart would indicate since the Gasoline powered coach will have a higher rear end ratio and the higher revving gasoline engine to be able to take the advantage of the higher rear gearing.

One other issue to take into account with a normally aspirated engine (non turbo) is that the air density will have an impact on the power generated by the engine. "On a hot day, or at high altitude, or on a moist day, the air is less dense. A reduction in air density reduces the engine horsepower." Link So on those hot muggy days a non turbo engine will have less power than on a cool dry day. Adding altitude to the equation will also rob power on non turbo assisted engines. Virtually all modern diesels in today's motorhome will have a turbo as standard equipment. The power loss in most situations is not really significant. The loss is in the order of 1 % per thousand feet up to three thousand feet then about 3 % per thousand feet there after.

There is one advantage to a diesel worth considering and that is the auxiliary braking that is available via either an exhaust brake or an engine brake. To my way of thinking the availability of auxiliary braking is a far more important advantage than any extra power. Having said that, the perspective I have is that at times it is convenient and others it is a margin of safety that I really appreciate. The thing to keep in focus that it is possible to adjust ones driving pattern to proceed in a safe manner without the need or desire of an auxiliary brake.

A diesel powered coach with a power to weight ratio that is superior to a gasoline powered unit will be able to pull grades at a faster rate and descend down grades more aggressively if equipped with an auxiliary brake. An engine brake being superior to an exhaust brake. But again the question is so what? Just what percentage of the on the road time will be spent going up and down grades where this is really a material issue?

There are Gasoline coaches that will out perform some diesel coaches in terms of pulling grades. As I mentioned the longer and heavier a coach gets the more that the need of a diesel comes into play. In this case the word need is a euphemism for desirable. Feeding that desire does have a price tag. The issue is determining the need based on the size coach and then working through the coast versus the benefit.

The only way to know is to figure out what you want in terms of size and floor plan which will include the added weight of sliders. If you are a driver instead of a parker and you want a large coach then a diesel may be the better choice if you are a parker then it may make more sense to go with a Gasoline powered unit in terms of price.

Our needs were such that a 40 footer was our choice which got us into a Diesel. For our traveling partner a 32 footer Gasoline unit is the perfect size he is as happy with his choice as we are with ours. We have traveled together extensively in mountainous country in all but the steepest of grades he is able to maintain the same speed with his vortec 8.1 as we are with our ISL 400. While I think he would like to have a larger fuel tank and would benefit from an auxiliary brake he is as happy with his coach as were are with ours. Our ride may be a little smother due to the air ride and the cockpit noise level lower when climbing grades but to him those issues are not enough to justify the price differential of his coach versus ours.

With the innovations in chassis design of gasoline powered coaches and the addition of 5 and 6 speed transmissions given the price differential of going the diesel route I would look long and hard at the gasoline powered coaches. The only way to know is to pick your size and floor plan then do a test drive.

One thing that you will find is for the most part all of us like what we have but there is always something "better". I would discount those who disparage one type versus the other... Or makes extravagant claims not supported by any logic of the physics involved in moving weight. But I would pay attention to those that take the time to go beyond this is bad and that is good.

I also think that we at times get lost in generalities so I would suggest that you get in the ball park with generalities but focus on specifics when you are in decision mode.

In general 🙂 a diesel pusher will be quieter in the cockpit area, will offer a smooth ride due to air suspension. Some diesel pushers will offer pass through storage. Most diesel pushers will have some form of auxiliary braking either in terms of an exhaust or and engine brake. (Diesel Engine auxiliary Brakes)

In general :)At some price point the interior fit and finish of a Diesel Pusher will be a step up... But for the upper end of the Gasoline powered units and the entry level diesel and up to some point along the DP price curve I do not believe there is much if any difference.

In General 🙂 the more expensive DP's will offer additional amenities beyond what is available on Gasoline powered motorhomes.

In General 🙂 Diesel pushers will have a longer range due to larger fuel tanks.

Here is a thread The power equation...Horsepower- Torque -Gear Ratio- Weight for those that want to ponder on this issue further.

JohnnyT

[zep]

I think I finally have hubby convinced that we won't live long enough to benefit from the extra cost or the 'if' better fuel mileage of a diesel. That said, reading this article is very interesting because I kept reading 'GM 8.1' which would be husbands choice over Ford. What is the difference between the Ford 6.3 and the Chevy 8.1?? which delivers better torque, horsepower and fuel mileage assuming units are identical?

I'm having a difficult picking out a 'used' unit, 2007 or new because so many are the Fords and I can't get the husband past this part.

Any help will be greatly appreciated.

PS: We currently pull a tt but it's a lot of work for him retiring in a year or so.

[Mikey360]

Just registered and this thread is the first one across which I stumbled. Lots of great information. Our 'new to us' 2007 Fleetwood Providence to be delivered soon. I'm looking forward to soaking up lots of help and contributing where I can.

[nostrings65]

...and then there is the bottom line...men who drive pushers think its the ONLY way to go and feel superior to those of us in the gas class A category....8 years fulltiming and I've seen it and heard about it more than I would care to....gotta have that torque and room enough for the wife's crap. Just sayin.

[driveby]

CDNEO1 wrote:
As part of my research, when the time comes I will be looking at gassers as well as diesels.. I prefer diesels simply as a matter of personal taste, but budget does weigh in my decision.

I believe that the V10 can haul **** as well as anything else on the road.

I will need a wheelchair lift, so I know that its been done both on Winnies and higher end diesels. but one thing I will be paying particularly close attention to is tires.. because its not unheard of for wheelchair conversion companies to ignore the fact that they're adding weight to the tires. Of course this occurred on my personal vehicle and not an rv.. but still..

not to hijack the thread but Winnie (and maybe others) have a whole division to accommodate wheelchairs and other needs for those that need such a mod.

[CDNEO1]

As part of my research, when the time comes I will be looking at gassers as well as diesels.. I prefer diesels simply as a matter of personal taste, but budget does weigh in my decision.

I believe that the V10 can haul **** as well as anything else on the road.

I will need a wheelchair lift, so I know that its been done both on Winnies and higher end diesels. but one thing I will be paying particularly close attention to is tires.. because its not unheard of for wheelchair conversion companies to ignore the fact that they're adding weight to the tires. Of course this occurred on my personal vehicle and not an rv.. but still..

[jdubya]

I only saw one mention of stability of the diesel pusher vs front engine gas. I would think that there would be considerably less trouble with swaying from a diesel pusher than with a heavy front gas. Not so? I have owned a diesel pusher 34' older motorhome (Itasca Suncruiser 1993) which I traded for a fifthwheel (39' Cedar Creek) because we wanted extra room when we lived in it for a year. I found that the fifthwheel was very stable in crosswinds, etc, compared to the motorhome, but I have no experience with a gasser front engine motorhome vs the DP. I am thinking about going back to a motorhome but we have already purchased the diesel truck and fifthwheel so we would take quite a beating in a trade down or else would have to pay too much to boot to go to a newer motorhome. I have seen 2000 - 2001 gassers in the $40k range and 1998 - 1999 diesels in the same range. We're afraid that we will lose too much living space to gain back the convenience of the motorhome.

BTW I have had both diesel motorhome and pickup and the diesel is not that hard to take care of. I change the filters and replaced the fluids on all of my vehicles. I have had more trouble with our 2008 Grand Caravan than with the 2003 Dodge Ram Cummins Turbo Diesel. (I had to put new brake pads around and fix the cooling system on the van already.)

[Seamutt]

Anyone got a diesel with couple hundred thousand miles on it, just asking.

[Skid_Row_Joe]

horizon451 wrote:
As far as maintenance you need to change the oil on a DP every 25,000 miles or one year whichever comes first. With a gas unit I think the number is every 5,000 miles. There are more filters to change on the DP than the gas unit. I have had both and prefer the DP. I also like the front door vs one right in the middle of the living area. I like the storage capacity and yes, I do like the torque of the DP.

Correct. Not to mention the gas engine would burn in the neighborhood of 20% more fuel in a DP give or take. My last diesel coach I put 150K miles on - I chose to have a diesel engine, which was the only way to go. The V8 gasser would have eaten me alive in fuel costs alone, not to mention it's higher maintenance costs.

[Skid_Row_Joe]

wickedinns wrote:
Thanks for the input. We are planning on doing extensive traveling for a couple of years at least. We hope to cross Canada and then tour as much of the USA as possible and then who knows from there.
Anyway we will keep looking and keep logging in to get more info from this sight (which by the way is full of info and VERY HELPFUL!!!! )

Thanks again

Wanda

You said the magic words "extensive travel." A 20% bump UP in mpg stays with you as long as you own and drive the coach. When in doubt, go with diesel power. A diesel doesn't need to be fed as often. And, the maintenance and associated costs are far less than a gas engine.

I'm 100% diesel, have been for 20+ years both cars and motorcoaches. I would never give up the better mileage. Diesels are for people that have done the math on costs.

[horizon36]

I would suggest that you drive similar sized coaches in gas and diesel. The diesel pusher (DP)rides on air bags and the gas on springs. The air will give you a smoother ride. The engine is in the back on a DP and so is the noise and heat. A DP is much quieter running under load than a gas unit. The carrying capacity of a DP is typically much higher than a gas unit. For extended travel you will most likely want at least a 36 foot coach. That size and weight on a gas unit will start to limit your carry capacity and not so much on a DP.

As far as maintenance you need to change the oil on a DP every 25,000 miles or one year whichever comes first. With a gas unit I think the number is every 5,000 miles. There are more filters to change on the DP than the gas unit. I have had both and prefer the DP. I also like the front door vs one right in the middle of the living area. I like the storage capacity and yes, I do like the torque of the DP.

[wickedinns]

Thanks...more food for thought...EH! hahahahaha... I drive a diesel car and LOVE it but of course it isn't a truck and diesel here is reasonable but since we plan to travel in the US that changes the situation. My diesel car is no more expensive than my gas car, as the mechanic I go to is local (not a dealership) and is very reasonable but MH are a whole other story from what I have been reading and advice I have been getting from other sources. Perhaps going with a newer gas model is best especially since we don't even know if it is what we want (I do but hubby is a whole other story). I hardly ever see diesel's driving by on the highways in these parts....they are always gas. I have a sister who owns a smaller gas and loves it(she is more of a parker and it is her first) and a brother who has a diesel and swears that is the only way to go (he is a driver and has owned a couple of each)..... ahhhhhhh.....and they BOTH want what is best for LITTLE sister!!!!!:S
Back to the drawing board.....

Love the input ...keep it coming....

Wanda 🙂

[jtment]

wickedinns wrote:
Thanks for the input. We are planning on doing extensive traveling for a couple of years at least. We hope to cross Canada and then tour as much of the USA as possible and then who knows from there.
Anyway we will keep looking and keep logging in to get more info from this sight (which by the way is full of info and VERY HELPFUL!!!! )

Thanks again

Wanda

Hi Wanda, We too are at about the same re-searching stage as you are, and have pretty much the same set of questions. I would like to shed some light on a few things that the Mrs and I have learned during our research. As a retired Teamster, drove Semis for 35 years, I always felt that the diesel was the only way to go. however, currently owning a 2009 Chevy Silverado Diesel, it hurts the wallet every time I hit the fuel station. I pay more for diesel than the highest grade of gasoline. I'm finding that the maint cost is much greater than that of a gas motor. Geesh, a fuel filter alone will run you $60, and I've learned that if you don't keep it changed at least every 10K miles, you run a high risk of blowing out your fuel injectors. By the way, those little babies will cost you around $375 ea, and there are 8 of them. That doesn't include the labor, and that will be near $90 per hour if your lucky. So besides spending way to much for fuel, and to keep it running clean, that weighs heavy on my researching.Of course there are many more items that should be compared, but operating cost in my opinion will limit travel somewhat. Diesel motors are not designed the way they were 20+ years ago, but the ride has. Again, in my day, if you had a spring on your seat, that was a luxury..lol. The overall ride of a pusher is fantastic. Drives like a Porsche and rides like a Cadillac, and you will always be the first up the hill if that impresses you. And if your going to travel in the mountains, an engine brake will save your brakes, and your concern of loosing it on a steep downhill. I'm wondering what else folks out there are comparing besides the performance of a diesel pusher. I like the looks from the outside myself. A 42'Monaco 3 Axel with a 500 HP engine looks and sounds like you have arrived, however, looks are not everything eh! Big windshields lets you see more while driving, but then allows a lot of sun in while crossing Canada Eh!!! Slide outs give you tons of room, but I expect they rattle like hell going down the road, and unless your doing more camping than driving, I don't quite see the need. I've read that there are a couple types of RV'rs, movers and campers. If your a mover, give me HP, looks, and ride. If your a camper, give me 10 slides and a hot tube!!! Somebody give me some thoughts here.

[wickedinns]

Thanks for the input. We are planning on doing extensive traveling for a couple of years at least. We hope to cross Canada and then tour as much of the USA as possible and then who knows from there.
Anyway we will keep looking and keep logging in to get more info from this sight (which by the way is full of info and VERY HELPFUL!!!! )

Thanks again

Wanda

[427435]

A 2000 or newer gas is likely good for 150,000 miles if maintained well.

In other words, it'll likely outlast the house part of the MH.

[JohnnyT]

Wanda, the longevity of gasoline engines have improved greatly to the point where I am not sure that longevity is an issue... The reason I say that is the amount of mileage that the typical RVer puts on their motorhome Gas or Diesel is fairly low.

If a gasoline powered motorhome meets all your other requirements I would not discount it on the basis of durability.

I would begin with asking yourself.. How many miles per year are you planning to travel... If you believe you are going to keep the motorhome for an extended time frame and you plan to put significant miles per year...then longevity will come into plan...

One other question I would ask is how much would it cost to replace the engine.

The diesel engine is designed to go more miles that a gasoline engine but for most the added longevity never comes into play...

JohnnyT