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Littlebeckets · 01-30-2006, 09:04 AM

Hi

Has anyone got any experience of converting a 35U Workhorse 8 litre Vortec to LPG. I was wondering where the recommended position would be for the location of the LPG tanks. I live over in UK and there is a very significant cost advantage to using LPG rather than petrol. The guy who is planning the conversion is suggesting that two 120 litres bottles are located in the space under the bed, but I am not too keen on that idea for several reasons!!!!!!!!!

Littlebeckets · 01-30-2006, 09:04 AM

Hi

Has anyone got any experience of converting a 35U Workhorse 8 litre Vortec to LPG. I was wondering where the recommended position would be for the location of the LPG tanks. I live over in UK and there is a very significant cost advantage to using LPG rather than petrol. The guy who is planning the conversion is suggesting that two 120 litres bottles are located in the space under the bed, but I am not too keen on that idea for several reasons!!!!!!!!!

MrTransistor · 01-30-2006, 12:16 PM

Hi Littlebeckets,
It seems to me that a conversion to propane or LPG wouldn't be cheep. My understanding is that one of the things that makes diesel more economical is that it weighs 7.01 Lb/Gal versus Gasoline at around 6.0 Lb/Gal. Since the energy content is similar on a per Lb basis, diesel starts out with a 15% advantage per gallon over gasoline. Since the diesel combustion process is inherently more efficient, the overall advantage goes to diesel at between 30% to 35%. You can do the math based on the price per gallon and your personal experience as to MPG for your type of driving at the prevailing fuel prices in your country or area.

As for LPG, the math is just the opposite. At 3.6 Lb/Gal, LPG even though it has a slightly higher energy content per Lb. comes in at 66%of gasoline's energy content per gallon. For the same range on LPG as compared to gasoline, you would need to carry half again as many gallons of LPG. For a Motor Home with say a 70 gallon gas tank, you would need over 105 gallons of propane or 380 Lbs. or 173 Kg. or 397 litters. Your mechanic seems about half right on the tank sizes but even with half the range on a fill-up, two 31 gallon propane tanks (remember the extra 20% for expansion) are going to take up a bit of room. That is exactly the size of the propane tank on our Horizon and I can't imagine finding a space for another one.

If you increase the size of the tanks to 62 gallons each to restore the range, the size gets to be unmanageable. I think that's why propane use here in the states seems to be limited to commuter vehicles and city busses. It's easy to fill up every 150 to 200 miles when you never leave the city. But for a 5,000 or 6,000 mile summer vacation, it doesn't make too much sense.

The other issue is the cost of the propane. Here in the US, diesel right now goes for $2.25 at some Flying-J's to $2.70 or more at many regular gas stations. Flying-J's current price here in Albuquerque for diesel is $2.36 per gallon. If you take two thirds of that to account for the energy content decrease of LPG, you get $1.55 per gallon as the break even price to switch to propane. Flying-J here has about the best price on LPG in town at $1.69. As you see, converting to LPG here in the states would require a healthy subsidy to cover the increased costs to operate plus the conversion cost.

In Great Britain as well as the rest of Europe, it may be that the tax on gasoline at the pump versus the pump price of LPG is such that this conversion can save you money in the long run. I knew that fuel was heavily taxed in Europe but if your taxes are that high, maybe instead of an LPG conversion, a change in politicians would be in order?

Littlebeckets · 01-30-2006, 04:57 PM

Thanks for the info , MrTransistor. In the UK the price petrol is $6.5 per US gallon compared to $2.5 for LPG, a huge difference. The cost of conversion is approx $4000, so it does make economic sense here in Europe!!

Hikerdogs · 01-31-2006, 08:34 AM

Conversion might make economic sense if you're only taking the cost of fuel into consideration. The total cost of operating an LP vehicle vs. a gasoline powered may not be all that much less.
A couple of years ago we had a leaking LP tank on our coach. It wouldn't have been so bad but it just happened to start leaking in a campground over the 4th of July weekend. All the kids with the fireworks made me a little nervous. We called the local propane supplier to see if someone could come out to drain the tank. When the guy got there he said he didn't have the capacity in his truck to pump off the contents of our tank since it couldn't be pumped off as a liquid. He took us to an abandoned gravel pit so we could vent the contents to atmosphere. While the tank was draining we stood off a considerable distance and observed.
As time went on we engaged in some conversation. I noticed the truck he was driving was diesel powered rather than LP powered. He explained that their previous fleet was LP powered but had some serious drawbacks. On the previous trucks the original gas tanks were replaced similar sized with LP tanks. Since there is less energy produced by the LP the cruising range was reduced. And since there isn't an LP station in every little town they had to go back to their own filling station every time they needed fuel. They were actually spending more time fueling their own trucks than they were servicing customers.
Another problem was the fact that the engines couldn't produce the power and torque necessary to pull the 20,000+ lbs of truck and equipment through the hilly terrain without having the pedal to the metal most of the time.
The last major problem he sighted was cost of fuel system maintenance. Apparently the regulators and other sensitive metering systems didn't like the continuous pounding on the backcountry roads and farm lanes. He said they were spending almost double the money on fuel system maintenance than they were paying for complete maintenance on the gasoline-powered trucks.
If the propane supplier didn't find conversion cost effective (buying LP at wholesale prices) I doubt that it would be for anyone expecting to use the coach in rural areas or where terrain could be a factor.

MrTransistor · 01-31-2006, 09:25 AM

Hi Littlebeckets,
WoW! That's around $4.50 total in taxes on a gallon of gasoline! Here, we pay $.40 to $.60 per gallon depending on how greedy the individual states are. The actual cost of the fuel at the pump minus taxes couldn't be that different. Crude, refining, transportation, and retailing should be about the same. Let us all know the details of how this works out for you.