WVO Conversion on my 1995 Dodge Cummins 4x4 Diesel Truck.

This page documents how I run waste vegetable oil (WVO) collected for free from restaurants dumpsters. They are glad to get it collected for free since they usually have to pay for removal in this area. WVO is different, simpler and better than making Biodiesel, because you don't need to do all the processing, which includes adding 25% Methanol (a poisonous, expensive fossil fuel) and lye, a hazardous strong base.

There is a forum with more information about this, and you can ask questions at:

The trick to run 100% WVO successfully without shortening your engine life is to run a 2 tank heated setup, and filter and dewater the WVO very well. Its possible without 2 tanks to run a blend of between 50-80% WVO, but its risky and could clog your filter, ruin your injection pump (IP) (or worse) in the winter depending on the WVO. And this is still an experiment where I won't know if the life was shortened for many years yet since these trucks are rated to last 350k miles before overhaul and this one has 140k after 12 years. Many people have driven >100k miles on WVO already. I am an engineer, so I spent lots of time studying the conversion kits sold by many companies, and many online forums, and came up with my own design which I think is more reliable, simpler, and cost far less.This truck from 94-98.5 is one of the best diesel engines to convert to WVO since its got a strong mechanical fuel injection pump. It burns cleaner than diesel and the exhaust smells like a BBQ grill.

Here is a diagram of my setup:

Here is a new, improved diagram of my conversion which adds the coolant flow:

The valves are through the floor by my foot so they are easy to reach. This model of valve
bought here works good this way since they have a long shaft to go through the carpet, insulation, etc. in the floor. No need for a remote cable or complex electric valves on a truck with lots of room under there. (and no fuel line in the cab) And its only 6" away from where the lines from the tank ran. Keep it simple and reliable is what I always try for. And I read dozens of posts on the forums by people having trouble with their electric solenoid valves failing and overflowing their WVO or diesel tanks making big messes. Which could be be a problem with this setup if you switch your valves into the wrong position.

I start the truck on diesel, or a biodiesel blend. Then once the engine is up to full operating temp on the dash guage, which depends on how cold it is, in the winter it usually takes about 5 miles, I switch both the tank and filter valves to Veg., and the return valve to looped. Most of the heat to get the WVO up to the recommended temp of >160 F comes from the 26 plate FPHE (Flat plate heat exchanger) right before the injection pump (IP). Thats why I placed the FPHE just before the IP. This is much more effective and gives quicker switchovers to WVO than many kit systems where they put a heat exhanger in the WVO tank and attempt to heat the entire tank. The WVO fuel line is heated from inside the Fuel tank all the way to the engine, by tapping into the coolant lines going to the heater core. This is because below around 30 F the WVO becomes like jello and won't flow. This is one reason why you don't want to dump WVO into your stock fuel tank. (And even at warm temps its bad to start an engine on WVO, it will cause coking (gumming up) of the rings.) My system has worked great at the coldest temps we got of -10F even with thick partially hydrogenated WVO that looks like non-pourable gravy which I use about half the time. Non-hydrogenated WVO is better if you can find enough of it because its easier to filter and dewater since it stays liquid down to about 35F.

This truck has a strong mechanical lift pump which is why I chose doing the valves this way to share it, to avoid the cost and reliability problems of adding another electric pump and electric solenoid valves for the WVO.

I put the filter on the pressure side of the lift pump to avoid air leaks which is a common problem I see many complain about when filters and connections are under vacuum. And its a hard problem to track down where the leak is.

Note in the diagram, you have to cut the existing injector drain manifold (small line) coming out of the top of the stock fuel filter and cap that line, and tee that line into the IP return line, so the small amount of WVO in there gets sent back to the proper tank. The stock fuel filter is in a hard to get at spot, so an advantage of this conversion is that I don't run much diesel anymore so that filter won't need to be changed for many years. I put the WVO filter where its easy to change, and get around 10k miles before it needs changing.

To purge the WVO from the lines before shutdown, I turn the tank valve to diesel, wait about 20 seconds which clears the lift pump and lines to the filter valve. Then I turn the filter valve to diesel, wait another 20 seconds for the IP and lines to clear, then turn the return valve to diesel. Then wait another minute or 2 before shutdown. This clears any WVO out of the system.

Here are the 2 valves where I tapped into the coolant lines for heat, with 2 valves so I can control how much goes to the WVO system versus how much to the cab heater. I have found this helps give quicker switchovers since I can have much more flow into the WVO side. Even in the coldest of winter, the heater core valve only needs to be slightly open, showing the effectiveness of this way to force more flow into the long set of lines going back to the WVO tank.

Here is the filter and the FPHE next to the battery, and you can see the WVO pressure and temp guage senders: (that all got covered with insulation after this pic) I have found the pressure guage is useful to get a warning that the WVO filter is starting to get clogged (when the pressure drops <10psi when you floor it) hundreds of miles before it starts to affect performance.

The valves on the floor:

Solar preheat on Veg.oil tank
I use the sun to preheat my black veg.oil tank
bought here , its working great. This size of tank (17 gallons) is nice since it fits to the side of the bed in front of tire wells and still allows the full bed length for my slide in camper as well as all the other 4x8 loads I need to carry.

It was 22F last night, and snowed 4". Today after the sun had been shining on my tank for ~1 hour only partly hitting it and 2 hours fully on it except for the bottom few inches blocked by snow, it was up to 72F WVO inside, 59 F measured at the North side of the tank, 95F South side. The tank is 17 gallons of WVO and was 7/8 full. Another tank which I left in the shade was 30F which is about what I would expect starting at 22 F and ambient is 36F now. And I haven't driven it in 2 days so no heat from that, and no sun yesterday it snowed all day.

So if you are in a cool, sunny place like CO, a black tank and solar can help alot.
Here is a pic:

Here is the fittings and coolant loop inside the tank, those are standard plumbing compression fittings on the aluminum tubes. An aluminum coolant line is looped through 2 of the existing bulkhead fittings, with a coil around the existing pickup tube. This has proven to be enough heat to allow it to work fine in extreme cold around 0F. This is far better than heating your entire tank, which can cause the veg.oil to oxidize and create particles to clog things up. Very easy to make, and the pickup tube is strong and welded to the bulkhead. And the big opening for the filler with bolts and gasket makes it easy to work on putting your heating coil into the tank. And then I drilled a hole and added a tire valve stem with the core out (on the left), and a tube connected to a fuel filter as a vent (not shown.)

Heated fuel filter

I am using a $8
Cim-tek 200 series filter which is 7" tall x 3.5" dia. with a 3/8 coolant hose wrap, tight and full height. I get over 10k miles between filter changes. Its $19 for head and filter. The fuel filter is heated by coolant running through 3/8" fuel hose wrapped full height around the filter and zip tied in groups of 3 hoses to hold it together when I remove the filter.

Tube in Hose fittings
Here is a link to a
Tube in Hose diagram with part numbers similar to how I did my heated fuel line from the tank to the front.


CAT recently did major studies of contaminant particle size in fuel and wear problems resulting. As a result they switched to 2 micron (absolute) filters, after their research determined 5-7 micron particles were the most abrasive.

Realize if you are filtering to 10 micron (nominal) that a large amount of particles greater than 10 microns can make it past. An absolute filter rating means 98.7% efficiency. A nominal rated filter without an efficiency rating (such as 70% of the particles down to 10 microns) is basically meaningless, and most are around 50%. A screen door could be considered a 10 micron filter, it will catch a 10 micron particle, once in a while.

If you have an older mechanical in-line injection its not as big a problem, unless you don't know the efficiency rating of your 10 micron filter. This applys both to your at home filtration, and the ones on your vehicle.

Here is a page about how I
filter and dewater my WVO using a centrifuge that filters it to a very fine micron level and is very easy to do with no replacement filters to buy.

Parts List

I did another conversion for my Mercedes, using this same design. Here is a list of parts from www.mcmaster.com that I am using (includes extras - always buy extras since you never know what you may change during install.)

black veg.oil tank (on the 300TD I used a plastic boat tank from ebay $50.)

Cim-tek head and filter-$19

26 plate FPHE - ebay $75

7833K73 Medium-pressure Needle Valve W/metal Seats, Brass, 1/8" Npt Male X Female.

5346K66 Brass Barbed Hose Fitting Barb X Male Pipe for 5/8" Hose ID, 1/2" Pipe, Packs of 5 -$10.20 Pack

5346K16 Brass Barbed Hose Fitting Barb X Male Pipe for 5/16" Hose ID, 1/4" Pipe, Packs of 10 -$9.85 Pack

50915K325 Standard Brass Compression Tube Fitting Adapter for 3/8" Tube OD X 1/2" NPTF Male Pipe 3@ $2.84 Each

5177K46 Easy-Bend Aluminum Tubing 3/8" OD, .305" ID, .035" Wall Thk, 25' Coil $25.10 Each

8682T23 Miniature Brass Through-Wall Fitting Female NPT X Female NPT, 3/8" Pipe Size -3@ $8.78 Each (only used if you don't buy a tank like I did which has fittings.)

50915K324 Standard Brass Compression Tube Fitting Adapter for 3/8" Tube OD X 3/8" NPTF Male Pipe -3@ $1.57 Each

5346K18 Brass Barbed Hose Fitting Barb X Male Pipe for 3/8" Hose ID, 1/4" Pipe, Packs of 10 -$9.45 Pack

5304K31 All-Flow EPDM Rubber Multipurpose Hose 5/8" ID, 1" OD, 300 PSI, Black 25'@ $1.27 Ft. -$31.75

4638K114 Low-Pressure Galv Iron Threaded Pipe Fitting 1/2" Pipe, Coupling, 1-5/16" Length, 150 PSI -2@ $2.33 Each

4638K455 Low-Pressure Galv Iron Threaded Pipe Fitting 3/4" X 1/2", Reduce Cplg, Fem X Fem, 1-7/16" L, 150PSI -2@ $3.01 Each

44605K276 Low-Pressure Blk Malleable Iron Thrd Fitting 3/4" X 1/4" Pipe, Reducing Cplg, 1-7/16" L, 150 PSI -$2.26

44605K274 Low-Pressure Blk Malleable Iron Thrd Fitting 3/4" X 1/2" Pipe, Reducing Cplg, 1-7/16" L, 150 PSI -$1.89

5346K65 Brass Barbed Hose Fitting Barb X Male Pipe for 5/8" Hose ID, 3/8" Pipe, Packs of 5 -$7.72 Pack

5346K21 Brass Barbed Hose Fitting Barb X Male Pipe for 3/8" Hose ID, 1/2" Pipe, Packs of 5 -$10.65 Pack

50785K152 Med-Pressure Extruded Brass Thrd Pipe Fitting 1/4" Pipe Size, Fully Threaded Nipple, 7/8" Length -2@ $1.11 Each

44605K449 Low-Pressure Blk Malleable Iron Thrd Fitting 3/4" X 1/2" X 1/2" Pipe Size, Reducing Tee, 150 PSI -$3.17 Each