Burning used oil through our engines - PeachParts Mercedes-Benz Forum

GregoryV022 · #1 10-25-2011, 02:13 PM

So out of curiosity, after i drained the oil from my 300TD, i decided to pour 2 gallons of it into my fuel tank to see if it would burn.

thinking back on that, im wondering if that wasn't be best of ideas.

please advise.

thanks in advance.

boneheaddoctor · #2 10-25-2011, 02:24 PM

Bad idea....there are a lot of contaminates including soot that are abrasive to the injection pump. So while it will run....for a while....you are going to shorten its life.

vstech · #3 10-25-2011, 02:27 PM

2 gallons will cause some wear, but mixed in with the tank it's not the worst thing as long as you don't do it on a regular basis. you tried it, it burned, don't do it again.
some members here have centrifugal cleaners for the oil, and they soot filter it, and use it as a fuel...
I'd not recommend it...

Mad_Matt · #4 10-25-2011, 02:30 PM

Oil is oil but used oil can be hard on the injectors and the injection pumps. It's full of carbon as well as other containments including additives and anything over 25 microns can cause damage. If you want to burn old engine oil I'd run it through a 10 micron fuel filter and mix is with diesel fuel to insure its viscosity, flash and pour points stay close to that of diesel.
I've considered doing the same thing in mine but don't have an electric FP with a filter head attached to run the oil through on it's way to the tank.

There are some oil bypass systems that run a small portion of the engine oil into the flue system to be burned. They all look like gimmicks to me.

vstech · #5 10-25-2011, 02:37 PM

... I'm thinking MUCH smaller filtration is needed for the IP to flow without damage than 10microns...
I'd be uncomfortable with 2 microns filtration on USED MOTOR OIL!!!
the BOSCH pump has REALLY tight tolerances.

Mad_Matt · #6 10-25-2011, 02:49 PM

I agree that more filtration is better but most Diesel Filters are only 25 microns. I'm still on the fence personally becaue of the other additives in engine oil.

vstech · #7 10-25-2011, 02:52 PM

I thought the primary filter was 25, and the secondary was 5 or 10?

Biodiesel300TD · #8 10-25-2011, 03:12 PM

There is a reason we use motor oil as a lubricant and not as a fuel. It burns really dirty. Think of the smoke from burning a quart or two in a few thousand miles, now imagine a gallon or two over 300-400 miles. Smokey and the bandit. Give a Hoot, Don't Pollute!

Best thing to do with it is to recycle it, or burn it in a waste oil heater.

GregoryV022 · #9 10-25-2011, 03:22 PM

probably should have clarified i had almost a full tank of fuel when i added the used motor oil. so it will have been diluted somewhat.

ive been running on this mix for about 60 miles now and if anything the engine runs smoother. but i hear that the general consensus is that unfiltered oil will cause undue wear on my IP and other internals.

is there any other course of action i should take at this time.

vstech · #10 10-25-2011, 03:47 PM

when you get the fuel down below R, I'd change the fuel filter... don't change it before you run out though. ( most filters catch the most when they are dirty...)

Diesel911 · #11 10-25-2011, 05:20 PM

Quote:

Originally Posted by Mad_Matt

I agree that more filtration is better but most Diesel Filters are only 25 microns. I'm still on the fence personally becaue of the other additives in engine oil.

The Secondary Spin-on Filter is listed as a 10 nominal Micron Filter. However, nominal Micron means it has a 50% efficiency rating at 10 microns.

BrianCostello · #12 10-25-2011, 05:26 PM

This habit came from the old diesel boats (like tug boats) of the 60's, 70's and into the 80's.

Some ships/boats had the used oil pump direct into the fuel tanks!! but you must realize it would be 15-20 gallons of used oil, into 2-3000 gallon's of diesel fuel about .01%

2 gallons into a 18 gallon tank is .11%. . . .a bit higher. and not advised. I say only run 1/2 tanks for the next 4 fill ups. So you keep diluting it.

Brian

Diesel911 · #13 10-25-2011, 05:27 PM

Despite the fact that I had advised against burning used Motor Oil as Fuel I tried out of curiosity; 2 quarts of used Motor Oil in my Volvo Diesel.
(However, I filtered it through a 2 nominal micron Filter Bag before it went into the Tank.)

It makes the Exhaust gas stink! And, it stinks even after the Tank was refilled with only Diesel Fuel.

Motor oil has additives in it to retard burning and used Oil can have acid in it.

It also has an Ash content to it. Ash content is actually Metal.

GregoryV022 · #14 10-25-2011, 05:45 PM

Filtering it probably would have been a good idea. ill keep filling up at half tank to dilute the mixture until the fuel in the inline filter comes through clear (its black right now). then i will change the spin on filter.

i sure hope i haven't done to much damage.

mach4 · #15 10-25-2011, 06:11 PM

As suggested, untreated engine oil is probably not a good idea for automotive diesel engines.

Years ago we were on a cruise ship (back before 9/11 when it was still possible to take tours of the engine room) and the subject of engine oil came up - I think in the context of "how do they change the oil in the ship's diesel engines?" And the answer was - "they don't. The engineer described a closed loop system where a portion of engine oil was removed on a continual basis and mixed with the fuel and burned with an appropriate amount of make-up oil added the crankcase continuously. Seems to make sense...

A recent article in the Seattle PI talked about the cruise ships in Seattle - "A lot of them burn what's called bunker-C , and it's so dirty and it's so black and it's so awful, they have to heat it until they can get it to the point where they can move it around the pipes. It's like tar". If that's the case, diluting the fuel with appropriately filtered crankcase oil seems highly appropriate. If this is true, then the only waste to be disposed of would be the used filters. Seems like a good design. Obviously, the system would have to be designed to handle the quality of fuel being used.

It would be pretty cool, though probably highly impractical, to have a closed loop system on our cars, where an oil change would consist of a filter change and adding motor oil to the make-up tank... and the only other maintenance maybe an oil pan flush every 200k or so.