Dave's Bus Conversion

Veggie Oil Fuel

Frequently Asked Questions


Table Of Contents

  1. Do people really do this?
  2. You can run a diesel engine on vegetable oil?
  3. Do you have to modify the engine?
  4. Seriously, this works??
  5. How much power do you lose?
  6. What about emissions/pollution?
  7. What about engine life?
  8. Won't your exhaust smell like french fries?
  9. Wow - how can I do this to my car?
  10. How difficult was the conversion?
  11. What's your projected cost per mile?
  12. How do you pick up the oil?



1:   Do people really do this?
Yes, people do this, and it works.

2:   You can run a diesel engine on vegetable oil?
Yes, if it's hot enough (sometimes even if it's not).
There are many ways to accomplish this, my solution is to startup
initially on diesel.  When the engine is hot, I use the hot coolant
to warm up the vegetable oil before injecting.

The oil should be at least 160 before injection, though many claim 
180 is a better target.  The engine stays at 180, so it's difficult 
to warm the oil fully up to 180 without electric heat.  I'll start 
with just coolant and I'll see what temperatures I can hit.

There's also the argument that the injectors are plenty hot and
will heat the oil past whatever my final temp gauge tells me.

3:   Do you have to modify the engine?
No.  I just add a second fuel system that is heated by the engine.

4:   Seriously, this works??
Yes.

5:   How much power do you lose?
None.  SVO has about as much energy per gallon as diesel fuel!
In fact, Rudolf Diesel originally invented his engine to work on peanut oil.

Here are some stats on different fuels:

                         pounds/gal  BTU/gal      cetan #   viscosity
                         ----------  -------      -------   ---------
No. 2 diesel               7.05      140,000        48        3.0 centistokes
100% Biodiesel (B100)       7.3      130,000        55        5.7 
Raw vegetable oil           7.5      130,000     35 to 45   40 to 50

The big issue is the viscosity, which we can reduce by heating.

6:   What about emissions/pollution?
Running SVO has significantly lower emissions than diesel.

7:   What about engine life?
Because vegetable oil maintains it's lubricity properties at
high temperature, engine life can actually be increased.

8:   Won't your exhaust smell like french fries?
What do I care?  My exhaust is 40 feet behind me, and I'm driving
away from it at 75 mph.  :)

9:   Wow - how can I do this to my car?
If it's a diesel, then it's possible.  Usually you need to process
the oil at home because it's difficult to carry around the equipment
that I have on my bus.  There are many solutions to be found on the web.

10:  How difficult was the conversion?
It's actually a massive project for a bus of this size.
I need to be able to dewater and filter fuel on the fly, and I need 
to be able to heat and transfer up to 1/4 gallon of fuel per minute.

11:  What's your projected cost per mile?
I get about 7.6 mpg whether on SVO or diesel, but that's mostly
irrelevant since the waste oil is free.  I have to replace the
filters regularly, about 1000 miles for the dirty filter and 4000
for the clean - these are drop in paper filters that cost about $10,
so I'm hoping to pay about $0.0125 per mile.  :-)

Since I can carry 270 gallons of oil (about 1 ton of weight),
I can hypothetically drive my 15 ton bus from Seattle, WA
to Miami, FL for about $42 with only one fillup.  Sweet!

12:  How do you pick up the oil?
This is pretty variable.  Most restaurants get oil in 5 gallon plastic cubes
called "carboys."  Many of them dump the oil back into the carboys and then
have them picked up after collecting a few.  Getting 15 gallons or so from
each restaurant would mean that I'd need to stop at about 20 places to fill
up, and that's assuming each restaurant gives me oil and has a full set to
dispose of.  Fortunately some restaurants have oil collection dumpsters
where they dump a hundred or so gallons before pickup.  From these you can
pickup large quantities of oil that's settled most of the water and debris
out.  The problem is, many of these dumpsters are actually owned by the
retrieval companies, so the oil is as well, and they're not too interested
in letting people take their business away.
The waste oil gets processed and filter by those companies and sold on a
commodities market.  The price today (9/2006) is about $.13/pound (with
oil being about 7.5 pounds/gal).  That's about $1/gallon.  My hope is to
start buying oil from the processors at $1/gallon, and cutting my fuel
costs by a third.  That's like making my 7 mpg act like 21 mpg.  On top
of that, the processed fuel is much cleaner, meaning that I don't have
to prefilter or change my filters much.  We'll see how that goes.


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