used motor oil as fuel

Discussion in 'Propulsion' started by Boston, Feb 5, 2012.

  1. Boston

    Boston Previous Member

    < thread split from to encourage this discussion to grow without fear of diverting the other thread. >

    I wouldn't think so but then again I'm probably not your best source on marine applications, Last time I touched a boat was about 35 years ago. yup lots of the old boats we worked on had dry exhaust specifically cause it was cheaper, but I wasn't exactly as accomplished a mechanic as I am today way back then either. From what I can remember it was pretty much set up just like a car. Radiator, antifreeze, exhaust pipe out the top with a flapper on it.

    On my own build I'm not even remotely considering the trouble or potential troubles of a wet exhaust system. Going dry all the way and using a heat exchanger right off the pipe to heat the fuel for better filtration. But then again I'm using used motor oil as a fuel so I need to heat it. Normal diesel you don't really need to heat in order to polish it up some. Although I'm sure it would help, specially with passive water separation.

    here's a couple shots of my heat exchanger on the exhaust pipe of the truck

    In the second shot you can see the y connector which brings hot exhaust gassed from the headers into a single pipe. Duel exhaust is more expensive and I wanted to equalize the pull from cooling the gasses with the heat exchanger. Otherwise I'd have ended up with two exchangers instead of just one.

    I could have just bought a heat exchanger, ( there about $600 ) but whats the point, I made my own ( cost me about $50 in parts and $10 in welding ) Two 5" to 4" reducers and a chunk of 5" pipe worked like a charm, after that it was just a mater of cutting a coupling in half for the hose connections and drilling the holes. I ran 4" exhaust pipe off the Y and then just used about a 4' section of 5" pipe to jacket the exhaust pipe with cold oil. Doubles as a muffler as well. Heat up the fuel so I can separate any water that might be in there more efficiently and then sends it on to the standard oil filters, which also work about a million times better with warm oil than with cold.



    I'd think if you were just running standard diesel you could skip all that. But I'm a cheap bastad and I'm not paying a dime for fuel if I can help it.
  2. Angélique
    Joined: Feb 2009
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    Angélique aka Angel (only by name)

    Bos, when the whole system is cold, do you start on diesel or do you have a seperate system to heat up the used motor oil for start ?

    I'm amazed, does it smoke . . . . :confused:

  3. Boston

    Boston Previous Member

    I start on diesel, but I could start on motor oil if I had a more powerful starter. The cold thicker fuel puts additional strain on the starter. Also my snap connect to the fuel heater in the filter is wonky so its not hooked up till I can cannibalize a new one of an old truck. And that particular parts really hard to find. Once I get everything all dialed in I think I could probably start on motor oil, but for now I start on diesel.

    And no, I spent some time and tuned it so it doesn't smoke when running the used motor oil. Which wasn't easy because I nixed the idea of using a centrifuge in the polishing system. Which would have taken out the free carbon from the oil and made it easy to tune for low smoke.

    It smokes when I go up into the mountains because of the altitude and I'm not running a computerized system. But at the altitude I tuned it for it doesn't smoke at all. I'm at about 6,000' in Denver and I am in the process of buying property up in south park, which is over kenosha pass at about 10,000' If I go much higher than that it starts smoking like a ***** but thats not the oils fault, its the oxygen content. When I ran it on diesel it did the same thing

    here's a shot of it as I was tuning it and you can see there is very little smoke, specially for a diesel running full bore

    OK enough of the hijack
    sorry Cat
    back to you mate and best of luck

    one more brief interlude
    I found 7 acres for 5k just down the backside of the pass from here
    I'm thinking fishing cabin since its about 5 miles from the miracle mile. Colors 2005/Kenosha Pass highway 285.jpg
  4. Angélique
    Joined: Feb 2009
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    Angélique aka Angel (only by name)

    About the used motor oil as fuel aside . . .

    The burning of used motor oil in a diesel engine amazes me but I'm also amazed about heating the fuel in a exhaust heat exchanger as I know of several fuel heaters for fuel efficiency reasons (don't know if the claims are realized) but they all use heat from engine coolant to heat up the fuel.

    Anyway, I think in Boston's system the oil is going to cool down while being transported from the exhaust heat exchanger to the fuel filters, there being filtered and then transported to the injection pump. Atomization and combustion might be improved if the oil gets reheated just before the injection pump.

    Here some examples of fuel heaters to put in a radiator hose (the hot one) which in Bos' project can be used to reheat the oil just before the injection pump for better atomization and better combustion . . . . .

    [​IMG] ---> Link.

    [​IMG] Fuel Pre Heater Project for 89 Ford Mustang - - And some more: link -- link

    Cat, sorry about the chitchat, please carry on with the original thread . . . . :)

    Bos, if want to elaborate on this or if there are more responses to come, maybe better ask the Moderator to make a split off thread about this containing the posts -- #1 -- #2 -- #3 -- #4 -- #5 -- and the ones that might follow . . ?

    Good luck !
  5. Boston

    Boston Previous Member

    fair enough
    hijacking is such an unsavory habit

    don't use copper for a fuel line
    not sure why but its supposed to be a big mistake

    I use all cast iron or aluminized steal like it the pictures of my gigantic heat exchanger

    Oh and they make reducers so you don't have to pinch stuff off like in that last picture. Bad craftsmanship will inevitably lead to more headaches down the road. Do it up right whatever you do and best of luck with it


    I sent Jeff a note just in case Cat wasn't enjoying our theft of his thread
  6. Boat Design Net Moderator
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    Boat Design Net Moderator Moderator

  7. CatBuilder

    CatBuilder Previous Member

    Yeah, I was going to ask if he could close it. :D:p;)

    Joking, of course. I didn't mind the drift, but thank you for being polite. :cool:
  8. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member


    I assume you are cleaning the oil before burning it..are you running filters?
    If so,I recommend a centifuge-it will remove everything down to fractions of microns.

    I have one of them on each of my Cummins,and haven't changed the oil in 3.5 years/460 hours.
    I'm not being cheap,I just like to have perfect oil and a by product of that is I just don't need to change it.

    Had the oil sampled last year and they asked me why I brought in oil with such little use on it.....
  9. Angélique
    Joined: Feb 2009
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    Angélique aka Angel (only by name)

  10. Boston

    Boston Previous Member

    I run a total of 7 filters on what starts out as waste motor oil. First thing I do is heat it up so it filters better, then it goes through a water separator several times, then two 20 micron rock strainers ( race filters, they don't do much but take out large chunks but they are very high volume and have 20lb pop valves, two 5 micron purilator filters and two 1 micron purilators. The system is designed to just run whenever the truck is running.

    It works well for veggie oil to but that stuffs a pain in the *** to find sometimes and being the cheap bastad I am I just don't feel like fighting it. So I use what veggie oil I can find to make bio diesel and mix it with the used motor oil. That and a little Kerosene later and the stuff runs great as a winter blend. In the summer I can run straight veggie or motor oil and as long as I watch my temps I'm fine.

    I have a centrifuge but the pressures you need to make it work properly are a little high for the standard oil filters I'm using and I'm a little funny on so much high pressure in the system

    I was thinking I might pull the fluid through the filters and then push it through the centrifuge but at that point I'm already down to 1 micron and all thats left is the free carbon. As you can see from the rev test in the previous posts there just isn't that much smoke coming out of this thing. So I'm not so sure I feel like going to all that extra trouble of adding a booster pump and a regulator just for the centrifuge that isn't doing all that much anyway

    who knows
    Once I run it some this summer I'll know a lot more about how its reacting to the new system, winters kinda a tough time to really know how it likes the new set up. Half the time its cold and the other half its sliding around in the snow. That and I'm not driving it that much till I get the body work and interior done. Snow tires would help a lot as well .


    Thats it from earlier this year when I was just running it on veggie oil. The water separator isn't hooked up yet ( the big tube on the right hand side ). The centrifuge if I end up installing it goes on top of that tube and the filters and separated fluids drop down to the gravity separator. Anyway you can see all the filters, goes orange white gold through the system and then drops back into the big tank, which is baffled of course to help keep filtered and unfiltered fluid a little better separated, Basically I let it run whenever I'm driving and for a few hours when I first fill up.

    I've got about 150 gallons of veggie oil in the back yard now and maybe 100 gallons of WMO in the tank. The tank holds 200 gallons and I've got another 40 in onboard tanks. so my range is about 3600 miles. I fill up twice last summer, one on veggie oil and one on motor oil. Which convinced me it was worth it to rebuild the truck. Maybe not from the frame up but it should end up looking new once its done. Hopefully sometime this summer.
  11. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    Looks like a great set up you have there.

    Reminds me of an old slant six/stick shift Dodge truck I bought,on propane.
    It had 700 litres underneath and I added another 500 in the bed and with the great mpg I could do 10,000 km/ 6200 miles.

    Many engine centifruges for machinery etc can run off of air..very little air in fact.
    I think .2 cfm.

    I don't know what you mean by high pressures...mine run off the engine oil pressure.
  12. Boston

    Boston Previous Member

    I got one that runs on 100psi, the rest of the system is independent of the motor and runs at about 20psi, an oil filter really shouldn't go over about 60 psi and most have a pop valve that bypasses the filter element if you get more than 5lbs cross filter difference in pressure. So the lower the pressure the better. Also makes a world of difference if you warm up the fluid.

    cool rig on the propane. Around here they are getting hard to insure because of the dangers of explosion. I get around that two ways, one I have farm plates, I can carry up to 502 gallons of just about anything, and my tank isn't directly hooked up to anything, all those hydrolic snap connectors mean the system can come out in about as long as it takes me to drive the fork lift over to it.
  13. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    Actually I had no fears about propane,with all the turn off valves,relief valves, and especially the excess flow valves.
    If a hose it cut it will only leak 10 litres an hour..enough to smell.
    And with the narrow fuel/air range for explosions I was fine with it.

    Propane would be great on a new vehicle with proper anti knock and higher compression I bet the power would be close.

    Anyways centifuge..somethin like this:

    There is one out there that runs off 12 volt to run the centrifuge
  14. Boston

    Boston Previous Member

    well those are pretty damn slick

    I got a cheap one and it arrived used and broken from Paba bio diesel. The thing cost me about $120 and it used pressure from an auxiliary pump. Its still sitting in its original box waiting to be returned. Problem is I welded up the water separator with that specific design in mind so once I get the system down I'll redo it out of aluminum. I'm still fiddling with it.

    Nice find on those filters though, If I can get one to work at under 40psi I'd be happy as a clam. Thing is again its just removing free carbon after it goes through all the filters I've got on this thing. Even have a wad of cattle magnets in the tank. Must have put fifteen or twenty of them in there right were the baffles cross so the fluid is forced to slowly flow past them constantly even if the system isn't running.

  15. Frosty

    Frosty Previous Member

    If I had a single cylinder Lister on a cement mixer I would use any damn oil I could get. But I would be more reluctant on my triple stage injected 16000 dollar Yanmars.
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