LP vs. gasoline. New generator in old Motorhome.

[colonelcorto]

Hello, I have a 1996 Southwind. At the end of the season last year, my 22 year old Onan bit the dust. I believe the alternator bit the dust. Luckily, there is an Onan repair center just a few miles away. If it cannot be repaired for a reasonable price, I am going to have it replaced. I am leaning toward the replacement as the generator burns oil and is prone to stalling on a heavy load.

My question is this: if I replace, should I choose LP or gasoline? The current generator is set up for gasoline. It draws from the 75 gallon fuel tank that is shared with gas guzzling Ford 460. Running the generator drops my fuel mileage by about 1 to 1.5 mpg. This is significant when I am only getting 5.5 to 7 mpg to begin with. I am considering switching to LP as the motorhome has a 24 gallon LP tank on board. This would extend my driving range, which I am happy about, but has me concerned about finding a place to refill the LP tank. Dual fuel would be the best of both worlds.

Any advice?

[LaTriker]

I filled up my gas pickup today at $2.18 per gallon. I also filled up the lp tank on the MH today at $3.50 + tax per gallon. If the gph consumption on a gas and lp generator are near the same, a gas gen will be much cheaper to operate.

[wvabeer]

Gasoline all the way, propane gen really consumes it more then gasoline. Gas is much easier to acquire.

[whizbang]

You have to go gas. You carry more of it and it's easier to come by.

[MrWizard]

it should be noted
the OP has his OEM LP tank, which is smaller than LP tanks mounted in DPs with LP generators,
I know the LP tank in the Safari is about 50% larger than what the OP has

thats the nature of the beast, when using an LP genny, you need a bigger LP tank

[wa8yxm]

Gasoline has more Whallop per gallon than Propane. And you carry 75 gallons of Gasoline v/s what 25 of Propane give or take a bit. I'd stick with Gasoline.

[BigRabbitMan]

One thing you need to consider is that a new gas generator will use less fuel per hour than your old one. When I changed my engine from gas to diesel, I had to change the genny to propane. Based on my experience I would stay with gas. By searching you should be able to find a relatively recent Onan Marquis Gold 7000 like mine for a reasonable cost. Quiet and nice. By switching to propane, it was de-rated to 6500 watts and uses more fuel. Someday, I will switch to diesel to get the genny to match the main fuel tank.

[RLS7201]

6500 Onan uses 1.2 GPH at full load on LP. 0.9 GPH on gas at full load.

Richard

[Rick_Jay]

OP,

Get the gas generator. Seeing as we travel with two dogs and 5 people, we have to run our generator when travelling in warm/hot weather to keep everyone comfortable. I don't think your generator draws more than 1 gallon per hour, and most likely, if you're just running one A/C, it's probably closer to 0.5 gallon per hour.

IF you're concerned about having to refuel as often, you might want to consider this option. IF you are diligent about it, you can have the generator pick-up tube in your gas tank lowered so the generator can run longer while you're on the road. I had that done to mine when I had the tank out to weld a leaking spot-welded baffle joint. So now the generator will run until there's only about 10 gallons left in the tank (instead of the 20+ with the original tank). With the old tube, by the time I was passing the 325+ mile mark on the tank, I needed to start looking for gas or the genny might. Now, I don't need to start looking until I reach the 375+ mile mark which allows about an extra hour on the road between fill ups. The obvious danger is that you run the risk of not leaving enough gas in the tank to get to a gas station if you're camping out in some remote area. We've yet to go anywhere there wasn't a gas station within 60 miles of us, plus I know better than to do that.

I do agree with most of what Doug says. He has tons of experience on these systems, and specifically, rigs of all eras, makes & models. His numbers are probably a good guide as what to one can expect on an "average" rig of your era.

I also agree with him that your rig has a pretty low resale value due to it's age. If you're not planning on selling, then this doesn't matter. But there is NO WAY I would ever buy any motorhome which had a generator that used a fuel OTHER THAN the main engine. It's MUCH EASIER to refill with gasoline/diesel than to get gas/diesel and then propane. When I've seen this done on factory motorhomes, it's usually on lower end diesels and I believe it's always done as a cost-saving measure because diesel generators are so much more expensive then gas or propane.

I fill our propane tank maybe once per year. I do use an extend-a-stay when camping in a fixed spot during cold weather. If the generator was propane powered, I'd be changing tanks way too often. Plus, as mentioned, the added PITA of filling with gas & propane along the way. I like to get my fuel and hit the road. I don't want to fill up with one fuel and then go looking for another. Maybe that's just me! 🙂

So, if you're counting votes, I'd say get a gas generator.

Safe travels,

~Rick

[time2roll]

I have virtually no experience with this but I would look at a second propane tank if you go that route.
If the second tank is not feasible then maybe stick to gasoline.

Maybe look at auxiliary gasoline tanks for more capacity.

[MrWizard]

Op
You want to compute it as mpg
Go ahead
But that is not correct
It is gal per hour
10 gal per hour for the drive engine at 60mph
And 1.x Gph for the generator ?

Total fuel consumption is more when running the generator... Yes
But the drive engine fuel use Did Not Change

Imo a gas Genny replacement, is your best choice

[dougrainer]

1.Your resale value of your motorhome is very low due to age
2. Since you plan to keep the RV and replace the genset, going LP will make your RV almost zero in value when you decide to sell
3. LP Gensets are the WORST for any RV Towable or Motorhome. They burn about 50 percent MORE liquid than a Gasoline Genset. Since the largest LP tank on a Gas or Diesel motorhome is at best 25 gallons liquid, you have about 20 hours of running on a tank of LP and this does NOT include running the other LP appliances
4. LP Gensets are also prone to LP regulator oil gum ups. The LP regulator for the Genset, not your coach LP regulator.
5. Running a GAS Genset on the road will pull no more than 1 gallon per hour at full load and odds are you will be pulling about 50 percent load
6. Running an LP Genset on the road will be depleting the LP very fast and you will have NO LP when you get to the CG. Doug

[colonelcorto]

valhalla360 wrote:
I suspect something is wrong with your math.

Assuming a 60mph cruise speed:
- at 6MPG, you are burning 10GPH
- If you lose 1 MPG, that means you are burning 12GPH
- So the generator is using 2GPH.

2GPH is a lot for a generator to burn. I'm not sure about your Onan but my Yahaha 2400 running the air/con continously gets about 5hrs/gal or about 0.2GPH, which wouldn't be enough to measure in terms of the MH MPG.

If true, your 24gal propane tank is only going to be good for a single night running the generator.

Assuming more realistic fuel consumption, I would go with the gas option. With the proliferation of pre-filled propane tanks, fewer and fewer places actually fill propane tanks, so it's a pain to deal with.

No, the math is good. 60 miles traveled divided by 10 gallons used is 6mpg. My generator is an onan marquis 5000 BGM. The rated max fuel consumption for this unit is 0.9 gph. I think it’s reasonable for this 22 year old unit to consume as much 1.5 per hour due to wear. 60 miles driven, divided by (10 gallons plus 1.5) is 5.22 miles per gallon. I know the propane tank would only give me about 10 to 15 hours of run time, which is why I would jump on a dual fuel if it were available. I have had a lot of trouble getting propane delivered while on extended stays, packing up and driving down the road is a real PIA just because you need LP.

[Triker33]

My 6500W LPG generator burns .75 gal per hour. It is fed off of a 40gal tank separate from the house LP tank.

Your 24 gal tank has a 19.2 gal usable. So if you don't use any LP for water heater, stove or refrigerator or furnace. Your generator may run around 25 hours before a LP refill will be needed.

If you plan to stay with going to a LP generator, put a Stay-A-While system on your tank.

Or just replace with a gas generator.

[jamesroadking]

Here are some of the Pros and the Cons of each. https://www.generatorjoe.net/html/genfuel.html