I disagree with your calculation for two reasons:

1) A lot of people do conversions because they need a new engine
anyway, so for many the calculation needs to be done on the "premium"
charged for a diesel conversion over a rebuild of their 1.9 or 2.1

2) My 2.1 syncro lists the gasoline requirement as 91 octane right
next to the filler neck, so I have to burn premium gas. In Canada this
generally means paying $0.07 to $0.10 MORE per litre for diesel.

The math still probably works out against the diesel but when I do it,
it will likely be for eco reasons and added (mostly flat) torque.

Chris

On 3/10/06, Pensioner <al_knoll@pacbell.net> wrote:
> Musing over conversions, one of my many talents, brings me to consider the
> cost-benefit scenarios.  Let's postulate that we drive 10000 miles per year
> just to use easy numbers.  Discounting the normal maintenance for both a
> converted vanagon and a non-converted vanagon, the costs of conversion seem
> to range from ~$14000 (not a misprint) in my case to perhaps $3000 for an
> average of $5000 (high but we have to start somewhere).
>
> If fuel costs over time are the principal reason for going to diesel (not
> fuel availability, or the desire to side with Willie on the BioDiesel
> concert) then it makes sense to look at the fuel savings one would enjoy
> over that 10000 miles per year.  Diesel currently costs about %10 more than
> 87 Octane and is likely to stay that way.  For $2.50/gallon 87 octane let's
> say and vanagon average fuel efficiency of 17 miles per gallon.  The gallons
> per year is easily found to be ~588 gallons times $2.50 gives $1470 per year
> fuel cost before conversion.   If you go with diesel the fuel consumption
> will probably be on the order of 25 miles per gallon.  For the same 10000
> miles per year you'll pay $1100 in fuel costs including the %10 higher price
> for diesel.  You will get additional range between fuel stops but you'll
> need it as not all fuel services feature diesel.
>
> In summary you'll save $370 per year in fuel costs for 10000 miles per year.
> How many years to break even on the installation is left as an excercise for
> the reader.
>
> Seems to be over ten years if your previously owned motor lasts that long.
> FTSOE let's say it does.  You will have saved $3700 towards the motor
> replacement.
>
> The above example is to be considered a conservative estimate process, your
> mileage, tolerance, costs, will no doubt be different.
>
> "If a man professes knowledge but cannot express that knowledge in numbers,
> then that knowledge is of a meagre and insufficient kind"  -- Lord Kelvin
>
> Numbers rule!
>