On this forum and others, I have seen people mention offhand that they have mixed their used motor oil into their fuel. I am pretty religious about frequent oil changes in my Diesel, and every time I do, and then go to recycle the oil, I wonder.

Those of you that do this, what steps do you take to filter that dirty oil ? What about having to heat the fuel tank and lines in cold weather, as with WVO ? Any performance issues you have noticed ? Any adverse effects ? How much oil would you use per tankfull ? How about used transmission oil ?

I'm using a high quality certified B20 blend from a major Truck stop near my home, the Jubitz, so I'm pretty sure I have IP lubrication issues with the new ULSD covered. It's more of a penny-pinching thrift kind of thing, that and I'm genuinely curious. Do some people actually do this on a regular basis ?

Thanks in advance, everyone.

Dumping used motor oil used to be a standard practice years ago at most truck stops. I've done it for years with no special treatment whatsover. The used oil has already been filtered by the engine oil filter. I dump it in my 700 gallon diesel tank that also has a filter on the pump. And, besides all that, any of my diesel trucks also have filters. Seems that's plenty, and I've never had a problem. But - I don't use a lot - probably never more than a 10% mix. I'll also warn you, that just a little used oil turns your whole tank of fuel dark. If a cop ever looks at it, I'm sure there will be questions asked.
In regard to winter - I only use winter-mix fuel at the pumps in cold weather - mostly because I cannot buy my own street-legal clear kerosene anymore - so I buy it at the station premixed. It gets down to 30 below here, and it's not worth taking chances with gelling. Even with good winter-mix - you're really taking chances when it's that cold. When possible, I won't drive any of my diesels when it's below zero. I have several diesel plow trucks - but usually when it snows the temps stay above 20 degrees F.

What is the benefit of doing this?

What is the benefit of doing this?

buying less fuel. :D

get rid of "waste" engine oil

lubrication of fuel system

.....

Hmmmmmm, I already use an addtive for the fuel system.

My tank holds 95L so I will be saving roughly 10 litres per fill up. Any power benefits?

I have put my used oil(engine and trans)right back in the fuel tank of every diesel I have.
(3 Duramax,2 Cummins,3 Cat,2 John Deere,1 International) with never a problem or ill effect.I have done this for about 15 years.
I have noticed about 2 psi. More boost on engines that I pull under a steady constant load. The oil seems to give an increase in power.

I have added oil to the fuel of generator sets and they hold on average about 3 kw more load. That is about 3.3hp or about 3% more horse power in this case.
I'll take 3% more power when it costs $0.

What type of oil are you using and adding back to your tank? Regular natural oil or synthetic? Has anyone ever tried adding synthetic to fuel?

I have added used 5w-40 weight Rotella from my trucks engine into its fuel tank, also added Mobil 1 form my Z28 to my trucks fuel.
I get used motor oil form my friend in roanoke, he lives at home b/c he is going to civial engineer school. He collects used motor oil form his dads, moms, trucks and his bothers and sisters' cars and give me as much as I want. Their oil choise is what ever is on sale at walmart.
Don't get used gear oil, break fluid or PS fluid. Used ATF from an auto is good to use also.

Mostly 15W40 Rotella T from heavy equipment oil changes, some 5W30,etc, as long as it is water free and not gotten dirt in it. I also use transmission fluid if it is from an oil change and not from a shelled out tranny. Have not tried much synthetic so I don't know the effects of it long term

I do alot of oil changes a week but the mess and hassle, not going to bother.

I dont do oil changes often but I hate taking the used oil to the auto parts store for recycling so I might try pouring some in the tank.