Adding Used Motor Oil to Diesel Fuel?

[Simi 60]

Originally Posted by 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.

How does the stray metal get through?
Why do you think diesels have multi stage filters?

[Simi 60]

Originally Posted by SarahBeth

Frankly, I find this attitude both short sighted and offensive. .

Better than tipping it in the ocean via the "magic pipe".
https://en.m.wikipedia.org/wiki/Magic_pipe

As a full time cruiser with no marina and no car, but at next change 100 litres of bypass filtered used oil aboard, how do you propose one gets rid of it?

[Midnight Son]

Cummins Marine, for it's larger series use https://www.cummins.com/engines/centinel to burn the old oil, allowing up to 4,000 hr before oil change, in conjunction with https://www.cummins.com/engines/eliminator a multistage filter/centrifuge system. This is for K block engines though, nothing smaller. At least to my reading.
All the best

[Boatyarddog]

Originally Posted by SarahBeth

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.

Thanks!
Good Folks Everywhere
Keeping oil out of the air and Oceans IS and has always been most important,
4 stroke technology was developed for that purpose.
No reason to back up on preventing pollution.
Cheers,
SV Cloud Duster

[a64pilot]

Originally Posted by Simi 60

How does the stray metal get through?
Why do you think diesels have multi stage filters?

The wear metals are of course fine enough to not be caught by an oil filter or they wouldn’t be in the oil to start with, but as any oil lab will testify, they are there.

First oil crisis oil was burned with fuel, anything to keep from buying fuel. It did in fact cause wear on the fuel injection system and it cost money, didn’t save any, and of course early 70’s those were old fashioned Diesels and no ULSD either.
Fuel filters do not remove every particle that can cause wear, they remove the majority of particles that cause wear, but just for starters there is no normal fuel filter that removes 100% of the particles bigger than it’s rated.
It’s a false economy.
I manufactured aircraft, this aircraft was Certified to burn both #1 and #2 Diesel as opposed to Jet, actual field experience proved that the dirtier fuel caused more maintenance in the form of increased fuel nozzle cleanings and cost money, not saved it.
Oil in fuel is the same thing, sounds like a good idea, but it’s not.

[Cadence]

Originally Posted by 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.

Why on earth would anyone want to add something removed for particulates and run it through a fuel system?

[Sailshabby]

Originally Posted by 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.

Worth a thread of its own, perhaps. Anyone using Marvel these days?

[Simi 60]

Originally Posted by a64pilot

the dirtier fuel caused more maintenance in the form of increased fuel nozzle cleanings and cost money, not saved it.
Oil in fuel is the same thing, sounds like a good idea, but it’s not.

Its what I suspected which is why I haven't gone down that path but it still doesn't help me get rid of used oil.

Hoping there is a waste oil container where we next come out of the water.

[thinwater]

Originally Posted by 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.

The EPA never did ban used oil for this purpose. They didn't need to. Truck line experience killed it, after which engine manufacturers, API, and ISO put the nail in the coffin. But it was primarily the truck lines and ships that that gave up on the idea.


On the face of it, it makes no sense to add dirt to a highly refined product. You can do it, with filtration, but it will only be financially successful anecdotally, not statistically.

[Boatyarddog]

Originally Posted by Sailshabby

Worth a thread of its own, perhaps. Anyone using Marvel these days?

Sure, but this is a top end lubricant, 60% mineral oil, not motor oil. You cannot filter out Chemicals that will deteriorate your fuel and engine.
As well add residue from combustion
Some things were not meant to be burned as an end result.
We burn used motor oil in our business.
Don't like it.
SV Cloud Duster

[a64pilot]

Originally Posted by Sailshabby

Worth a thread of its own, perhaps. Anyone using Marvel these days?

I use it for a lot of things, but I don’t add it to my boats fuel, however I’ve seen R-1340 aircraft radials that would stick exhaust valves without it. I believe it’s not much more than stoddard solvent and something to make it smell nice, and I’d say it’s pure snake oil, except I have seen it work on old aircraft engines.
It was first formulated I believe way back when by the manufacturer of the Marvel carburetor to keep it clean, and when I say way back when I’m talking pre WWII I think.

It’s a great air tool oil. Isn’t real oily and smells nice too, and does clean out the mess air tools accumulate from oily wet air

[GordMay]

Originally Posted by a64pilot

The wear metals are of course fine enough to not be caught by an oil filter or they wouldn’t be in the oil to start with, but as any oil lab will testify, they are there ...

Originally Posted by thinwater

The EPA never did ban used oil for this purpose. They didn't need to. Truck line experience killed it, after which engine manufacturers, API, and ISO put the nail in the coffin. But it was primarily the truck lines and ships that that gave up on the idea.
On the face of it, it makes no sense to add dirt to a highly refined product. You can do it, with filtration, but it will only be financially successful anecdotally, not statistically.

Well said, both.

[TKDSailor]

Originally Posted by Sailshabby

Worth a thread of its own, perhaps. Anyone using Marvel these days?

FWIW (and off topic), one comment on Marvel Mystery Oil. I was trying to figure out whether my rings were leaking oil, or if it was the valve stem seals by taking a compression test on the cylinders (6 cylinder gas engine), then putting oil in the cylinder and checking compression again to see if the oil sealed the cylinders and gave me better compression (hence, bad rings...). I didn't have any 30W oil, but the Marvel was close by, so I tried it. It EXPLODED! Shot the rubber tipped compression gage right out of my hand, and scared the crap out of me! I don't know if this is an anomaly, but I would guess that when, even at the low compression ratio of a gas engine, the Marvel oil explodes when compressed...

[KP44]

Most engines will burn the old oil. If it's only 2%, there should be no problem burning the mix.
But why mix dirty oil into your clean diesel? Would you mix dirty diesel in with clean diesel just to save a couple euros or dollars?
I save my used lube oil to donate for recycling. If I ever install another diesel stove, I might filter the waste oil and mix it with stove diesel. But even after filtering, I would not pour it into my clean diesel tanks.

[captlloyd]

Originally Posted by TKDSailor

FWIW (and off topic), one comment on Marvel Mystery Oil. I was trying to figure out whether my rings were leaking oil, or if it was the valve stem seals by taking a compression test on the cylinders (6 cylinder gas engine), then putting oil in the cylinder and checking compression again to see if the oil sealed the cylinders and gave me better compression (hence, bad rings...). I didn't have any 30W oil, but the Marvel was close by, so I tried it. It EXPLODED! Shot the rubber tipped compression gage right out of my hand, and scared the crap out of me! I don't know if this is an anomaly, but I would guess that when, even at the low compression ratio of a gas engine, the Marvel oil explodes when compressed...

My guess it was more of a hydraulic episode rather than an ignition one.