Not familiar with your app but, I have never seen a
situation like yours with limited use where the economic
aspects of the project are not prohibitive.  For a low
mileage application, it would take many years to realize a
return on investment from fuel savings.  Maintenance expense
is not likely to be much different.  It is not likely that
the salvage value of the old engine is going to be anywhere
near enough to cover the cost of the replacement components
and, by the time you add in the labor cost for the project,
there is just not much probability that the project is
feasable on a low useage application.

Lugnut

Lugnut makes some very good points.  It could be done, sure.  But the
cost of acquiring a good motor and fitting it to the existing bus willl
be high.  Mating the engine to the rest of the drive train will be a
challenge too.  Since you will be downsizing the powerplant you may
have to find a way to offset the reduced power available to push that
big bus around.  Replacing a lower geared transmission, adding a
brownie box or dropping the rear end gearing are all expensive
possibilities for giving your bus enough power to negotiate hills at
25mph and do something as simple as pull out of a rut  or back out of a
ditch.

If you plan on leaving the motor running to supply power to the mobile
office when parked you might look into adding a separate
motor-generator unit as used in motor homes.

You need to do a cost-benefit analysis before proceeding I think.
Compute the difference in actual fuel usage, difference in maintenance
costs (likely minimal) for five years.  Then subtract the cost of a
conversion.  I think you will end up with a very large negative number.

Keep in mind that a diesel engine is far more efficient at part
throttle operation than a gasoline (Otto cycle) engine.  You may not be
wasting as much as you think.

Remember that the engine will still need to do the same amount of work to
move the same amount of weight. As long as you don't leave the engine idling
for long periods I doubt you'd ever see any kind of savings swapping out to
a smaller motor.

4 litres doesn't seem large for a bus engine, BTW.

Your money would be better spent simply making sure that the tires were well
inflated and that the motor was tuned up.

If cash is a real concern then use a real trailer and just use a truck to
move it when necessary.

Wrong economic reasoning.

Who cares about the wastefulness of a one minute operation that happens
once a week?

Do you think that the few drops of fluid that you save over the
remaining lifetime of the bus will ever recover the cost of the engine
conversion?

DOH!

So its overkill. If its going to be so rarely used, the lifetime cost of
feeding the bigger engine a little more fuel would NEVER be more than
the cost of trying to replace it. Why bother???

dances_with_barkadas@yahoo.com wrote in article
<1167989227.474225.310780@s80g2000cwa.googlegroups.com>...

Yet another shade-tree engineer overlooked, somehow, by the major vehicle
manufacturers of the world............