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Old 04-15-2010, 08:08 AM   #1
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Default Diesel vs. Propane Generator

We are in the process of purchasing a Fleetwood RV but do not know which type to buy, one with a diesel generator or one with a propane generator. I was told by the dealer that the diesel generator was better (that RV was more expensive) because it was more fuel efficient.

Another concern is whether you can smell diesel fumes with a diesel generator, in the RV.

What are the advantages and disadvantages of both types?

Thanks! Any help in this matter is greatly appreciated!
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Old 04-15-2010, 03:33 PM   #2
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Default Re: Diesel vs. Propane Generator

I have owned 14 RV's in the past 40 years. At this time I own a 40ft Beaver Patriot Thunder 425 that I use to tow my Forest River M B Cruiser Class B Sprinter motorhome. Maybe my findings might help you.

The Beaver is a diesel with a diesel generator. The Sprinter has a propane generator (because it could not be ordered with a diesel).

In a nut shell you want the diesel generator, regardless of cost. For the past 20 years, I have traveled into areas of the USA that have been destroyed by hurricanes, earthquakes, tornados, etc. There is no electricity for weeks or months at a time. I have to use a generator for both my work and my home (so to speak).

The diesel is less expensive to run (estimated 30% less) , but that is not the deciding factor. I find that the diesel will run longer because you have more diesel on hand, so you have to fill up less offen. The propane companies are hard to find and darn near inexcessible in a large motorhome. On the other hand, most stations that sell diesel have an area that is easily accessible to large coaches.

Although your costs may vary, the majority of the propane generators I have had wornout quickly and after repairs the cost exceeded the cost of a good diesel. For example at Hurricane Ike in galveston, I had to replace the stator (spelling) in the Onan propane generator in the Sprinter. The cost was $ 1,900.00. That was painful for a generator that cost $ 3,000 when new.

As to smelling fumes, there is no difference between diesel and propane. Just make sure the exhaust is on the drivers side and is close to the front of the coach (as far away from the bedroom as possible)

The Onan "Quiet" series of diesel generators are the best choice for many reasons. Any Cummins truck dealer, and most RV companies can work on them. The cost per hour for maintenance is probably half what any propane unit takes.

Mike Stephenson
2004 Forest River M B Cruiser
Lubbock, Texas
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Old 04-15-2010, 11:39 PM   #3
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Default Re: Diesel vs. Propane Generator

Thank you for your response! The information you provided is very useful!
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Old 04-16-2010, 07:43 PM   #4
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Default Re: Diesel vs. Propane Generator

If you plan on using your generator a lot then go for the diesel...otherwise the LP unit is fine.

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Old 07-13-2014, 05:08 PM   #5
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Default Re: Diesel vs. Propane Generator

I have a diesel rig and a diesel generator. Everything works great. Low noise level and no smell. after you choose between a gas or diesel engine... and unless you are ordering a new unit... go for the best unit at the best price. Happy Hunting!
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Old 07-13-2014, 07:17 PM   #6
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Default Re: Diesel vs. Propane Generator

Diesel is a trade off between nois, efficincy and exhaust smell. The other issue with diesels is that they do not perform well when lightly loaded for long period. They lose efficincy, when loaded lightly, (under 50% ish), and then they are subject to "wet stacking" which is an accumulation of unburned fuel in the engine and exhaust leading to some pretty significant issues.

Personally, with all the faults of LP I would go with LP UNLESS I was going to run the diesel near capacity most of the time, and could live with the noise and exhaust smell.

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Old 07-13-2014, 08:13 PM   #7
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Default Re: Diesel vs. Propane Generator

Only real disadvantage of the diesel is initial purchase price, about $4,000 more than propane.

As far as advantages go, you'll hear some 'I'll never have a propane generator' comments and they may have merit with respect to commercial work or a large Class A RV, but in a Class B or small C... not so much. Commercial work and private use are different applications and have different answers.

In terms of longevity there's not going to be much difference between the Onan 3600LP (propane) and 3200QD (diesel) because they are both air-cooled 3600-rpm engines. The typical water-cooled, 1800-rpm diesel gensets found in Class A RVs will have a longer life, but that's not what we're talking about here, apples and oranges.

Runtimes also won't be all that much different. The diesel generator can only use the top 3/4 of the fuel tank (about 19 gallons in a Sprinter), and even that assumes that you will arrive at your destination with a full tank. Arrive with half a tank and you may only have 7 gallons available. Diesel gensets uses less fuel so that is an advantage, but bottom line depending on how much fuel you have available in your main diesel tank and the size of your propane tank you may or may not have longer runtime with the diesel. Also while runtime can be very important in a large Class A where you might need to run the A/C all day long to keep the coach cool when driving, this is almost never necessary in a Class B/small C as the dash air is usually adequate. Plus, a large Class A might have a 150-300 gallon diesel tank providing a significant fuel capacity advantage over propane, not 26 gallons as with a Sprinter. Again, apples and oranges.

The one factor that remains is that a diesel genset means looking for propane less often (if you use the generator a lot) That's not usually a problem in the US so not really much of an issue, and whether it's worth an extra $4,000 to you for the occasional convenience is a personal decision. IMO you would have to use the generator a lot for it to be worth it, and in a small RV in a non-commercial application you probably won't be unless for some reason you frequently need air conditioning for very extended periods while stopped. Most everything else is best done with an inverter so solar may be a better place to put the money.

So, if you do insurance adjustment work in disaster areas or do pet grooming (you know who you are ;) then you probably want a diesel. For private use it's much more of a mixed bag due to the high initial cost of the diesel vs. the relatively few, really only single advantage in a small RV.
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Old 07-13-2014, 08:16 PM   #8
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Default Re: Diesel vs. Propane Generator

LP for me... Quieter due to less vibration and resonance; less stinky (diesel is really noxious to me); doesn't use your RVs fuel supply (which is important in a Sprinter w/ 26 gallons total and the last 1/4 tank is not accessible by the genny) vs a Class A with 300+). LP is available... But you have to think and plan ahead!

For a Class C where the power loads are generally light to moderate, or occasionally heavy, LP is my choice.

Less maintenance on the LP as it's cleaner.

Down side is that in very cold weather, you may have trouble due the cold decreasing the LP vapor available.
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Old 07-13-2014, 08:46 PM   #9
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Default Re: Diesel vs. Propane Generator

I chose to keep things as simple as possible and consolidate wherever possible. By eliminating the need to provide for two very different fuel supplies, a diesel will also save time and frustration every time you go through your "get ready to get on the road" check-list. If the gauge says full, you are done with fueling. The most significant issue for me however has nothing to do with convenience, cost, or performance... Diesel fuel is not under pressure in your small, enclosed, sleeping quarters, and if your system springs a leak, you won't wake up dead. You won't wake up to a Big Boom either... just before the lights go out for the last time.
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Old 07-13-2014, 09:20 PM   #10
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Default Re: Diesel vs. Propane Generator

You indeed have subtle way of describing the facts...ha!
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