Adding Used Motor Oil to Diesel Fuel?

[CapnCrunch]

I have found casual mentions of the practice but can's seem to find a full thread on it. I gather that it not a recommended practice for newer engines but I haven't seen any negative comments about doing it with older diesels.

I also gather (again only casual mentions) that the used oil should be kept to around 1% of the fuel volume.

Does it cause operation problems?

Does it adversely affect fuel economy?

Is it illegal anywhere?

I would rather have posted this to the Trawler Forum because Trawlers tend to have larger tankage, but I cannot get their system to log me in so I thought I'd go ahead and ask y'all.

[Alan Mighty]

Why dilute diesel fuel with used crankcase oil that likely is contaminated with metals, combustion products etc?

If your aim is to add lubricity, then surely a clean out-of-the-retail-jug ashless oil, such as oil designed for a 2-stroke engine, is what you would use.

And then there is the question of to what level you can safely dilute your diesel fuel. 1%? or perhaps 0.5%?

Oddly enough, you don't need to guess about such things. There are a few studies that have resulted from applying the scientific method.

Take a Captain Cook at: https://www.fuelexpert.co.za/2-strok...ical-study.php

[Wotname]

My concern would be possible contaminates but I suppose if it gets though all the fuel filters then it shouldn't be a problem.

As for dilution of the diesel, I don't see this as a problem assuming you have an old style engine (not common rail etc). The engine would run OK with 50% oil but might be smoky .

At 1%, the engine wouldn't notice it.

EPA folk might not like it but...

[CapnCrunch]

Originally Posted by Alan Mighty

Take a Captain Cook at: https://www.fuelexpert.co.za/2-strok...ical-study.php

I prolly should have stated that my reasons for researching were 1) as a more economical use for what would otherwise be a waste product and 2) a possible way to at least marginally improve my fuel expenses in my 1983 Perkins 4.236 engines.

The link you provided discusses addition of new 2-cycle oil to newer engines, so wasn't really relevant, but thanx for the effort.

[thinwater]

The blending of used oil in with diesel and marine diesel was manned by ISO (8127) decades ago. Specifically, the metals and higher ash content causes trouble, far more than the savings justify (at 100:1, there is no savings to speak of either).

This was something that was tried in the distant past when fuel was more expensive and recycling was less available. Makes no sense now. It's a dead horse, like adding pepper to antifouling paint.

It is not legal for on-road use.


Used oil is NOT a waste product. You may not be paid for it, but in larger lots the value to rerefiners approaches that of virgin oil.


(I was a chem e in the industry for 35 years)

[Lepke]

I burned used oil after good filtering for about 50 years. I mixed about 10:1. If you think about it, a diesel will run on straight oil.

I centrifuge and test my oil now, so no longer burn because I have no waste oil. But in the past have burned waste oil in ship engines, tugs, and small engines, like Detroits. Because I've used bypass oil filters or centrifuges since the 1960s, my oil is cleaner than most. My engines went longer between overhauls than other operators, so I never saw a downside to burning oil. Burning waste oil is a common practice in larger commercial boats and ships. No idea what the EPA thinks of burning waste oil, nor do I care.

[fatherchronica]

I would want an open end wrench sized to bleed the injectors hanging right there and maybe a couple of fuel filters inline. Having an engine die can sometimes be pretty hairy and I usually do all I can to try to minimize rushing around in a panic.

[roland stockham]

The engine may be fine with it but on stray bit of metle can wreck the high pressure pump. Why do you think deisels have multi stage filters? Personally the risk/benift would not be worth it.

[Boatyarddog]

Originally Posted by CapnCrunch

I prolly should have stated that my reasons for researching were 1) as a more economical use for what would otherwise be a waste product and 2) a possible way to at least marginally improve my fuel expenses in my 1983 Perkins 4.236 engines.

The link you provided discusses addition of new 2-cycle oil to newer engines, so wasn't really relevant, but thanx for the effort.

As oil is recycleable, why not take it to a auto repair store or?.
You'll encounter, problems with this experiment.
Increased deposits on valve faces and excessive coking.
Oil rings on your Pistons are to remove oil from excessively adding to Exaust and causing problems.
IMHO NOT a good practice.
Cheers
SV Cloud Duster

[Boatyarddog]

Originally Posted by thinwater

The blending of used oil in with diesel and marine diesel was manned by ISO (8127) decades ago. Specifically, the metals and higher ash content causes trouble, far more than the savings justify (at 100:1, there is no savings to speak of either).

This was something that was tried in the distant past when fuel was more expensive and recycling was less available. Makes no sense now. It's a dead horse, like adding pepper to antifouling paint.

It is not legal for on-road use.


Used oil is NOT a waste product. You may not be paid for it, but in larger lots the value to rerefiners approaches that of virgin oil.


(I was a chem e in the industry for 35 years)

Thanks for this most informative post.

[OS2Dude]

Originally Posted by Lepke

I burned used oil after good filtering for about 50 years. No idea what the EPA thinks of burning waste oil, nor do I care.

Perhaps you should start. Yes, the EPA can be overly picky about things. No, your vessel by itself does not make much of an impact on the would wide environment. But is everyone pollutes because it is easier, cheaper, and their 'outa-sight, outa-mind' mentalities then the impact is much greater, especially on the local environment.

[lorenzoj]

Adding used motor oil to fuel tanks is an old practice that has almost been discontinued.
In the mid 1970's GM tested 2 stroke Detroits with a high concentration (>10%) of used oil in the fuel tanks, and concluded that this practice would not affect the warranty.
I owned 671 detroites in triaxle dumps, and every week or 50 hours, we would drain a gallon of oil from the crankcase and filter it to the fuel tanks. The fuel tanks were in the 90 to 100 gal range. The oil filter was changed based on pressure drop across the filter (we used 10 PSID as our change criterion). The oil was never changed, and this practice kept the oil quality in the crank case at a continuous high quality level as opposed to the highs and lows on a regular oil changing routine. We used Delo 100 straight 40 wt oil.
I have 671 detroits in my current boat, which I have owned for 20 years, and I still use Delo 100 40 wt. I do not add the motor oil to the fuel tanks anymore because todays low ash, low particulate fuels may give unpredictable results with the addition of motor oil.

[moctrams]

Old diesel mechanic told me because of the low Sulphur diesel fuel these days I should add Marvel Mystery Oil to my fuel. I do it every time I refuel.

[GordMay]

To ensure that the diesel-waste oil mixture is suitable for use in a diesel engine, and that the emissions from the mixture will not be harmful to human and environmental health, it is important that the following requirements are met:
The waste oil must have been generated from a diesel vehicle;
The waste oil must be uncontaminated;
The waste oil must be filtered to a 10 micron maximum rating;
and
The concentration of waste oil in the waste oil-diesel mixture must not exceed 5% by volume (i.e., no more than 5L of waste oil per 95L of diesel fuel)


Under § 80.522, used motor oil, or used motor oil blended into diesel fuel, may only be used in the fuel system of model 2007 or later diesel motor vehicles, if the vehicle or engine manufacturer has received a Certificate of Conformity under 40 CFR Part 86, that certification is explicitly based on emissions data, and the motor oil is added at a rate consistent with the Certificate of Conformity. Under § 80.525, kerosene that a kerosene blender adds (or intends to add) to 15 ppm sulfur diesel must meet the 15 ppm sulfur content standard, as indicated by product transfer documents or test results.

[SarahBeth]

Originally Posted by Lepke

No idea what the EPA thinks of burning waste oil, nor do I care.

Frankly, I find this attitude both short sighted and offensive. As sailors, we know better, and first hand, how degradation of the oceans is impacting life on earth. WE are (or should be) its first stewards. That means we need to pay attention to the impacts of our actions on the health of the seas. The Environmental Protection Agency studies these impacts and makes its pronouncements accordingly. So not caring about these regulations - which are based on a desire and duty to PROTECT the oceans - is self-defeating. If you don’t care about it for yourself, how about thinking about your children - or the occupants of low-lying kingdoms and countries in Polynesia and elsewhere who are dealing with the impacts of selfish actions now.