Just how dirty recovered fuel oil is

vtfarmer

A somewhat frequent topic on this site is homeowners with partial tanks of fuel oil trying to either replace the tank but keep the oil they have or do something similar. A common refrain from the oil heating pros is that this oil should not be reused, and a not so common rebuttal from craftier homeowners or me, a farmer with numerous off road diesel machines to feed and decades of experience doing it, is that with the right filtration you can reuse the oil but you need to know what you're doing to not have a problem. Well, I did a little experiment I figured I would write a post about.

First some background: for those who aren't aware, modern ULSD (ultra low sulfur diesel) is the same thing as home heating oil (with the red dye to indicate that it is for nontaxable use only, which in the US means it may be legally used to run offroad and stationary diesel machinery.

I recently recovered about 150 gallons of fuel oil from a home converting to a heat pump (two trips with a pickup bed transfer tank to keep it DOT legal), and went through my usual process of pumping it through a 10 micron filter coming out of the tank then through a fresh 10 micron filter going into my bulk tank, and finally through another 10 micron filter going into the fuel tanks on my machinery. All of my equipment has primary and secondary fuel filters which I change reasonably frequently (for a farmer, meaning more than once a decade lol).

This oil seemed particularly dirty so I pumped some into an empty drink bottle and let it sit in my shop for a while. After about a week it looked like this:



It may be hard to see, but the entire bottom of the bottle if full of dirt that's settled out. This is filthy oil! And I don't know how much material is still in suspension. If I avoided paying the coop about $5/gallon for offroad diesel then my 150 gallon haul was worth $750, mins two new transfer pump filters ($10 each) minus working around not drawing fuel from my bulk tank for a month to try to settle as much of this crap out as possible, minus changing the fuel filters in the equipment I filled from the tank before I realized how dirty this oil was. Oh, and my time, but a person's time is never valued when farming, right?

Maybe this juice isn't worth the squeeze.

Jamie Hall

I might add, @vtfarmer , that if ANY of that dirt gets into the injectors on your equipment, they're toast. If it's at all hard, it's not very kind to your high pressure pump, either. That's why you have all those filters.

The other problem with reusing oil is the possibility of water contamination, and -- related -- molds and slimes. That's why there is a water separator on your diesel fuel system (I hope) and why you pay attention to it -- on some types of injectors, a slug of water will cause catastrophic damage (if you're lucky, it may not destroy the engine -- just the injector). The related molds and slimes will just clog the filters quickly, which results in silence...

HomerJSmith

Pump it thru a Frantz toilet paper filter, removes water, too. Takes it down to much less than 8 microns. Or might try to pump it thru a reverse osmosis filter set up, 3 filters. One 5 micron, two 1 micron. Might work. It takes time to filter, the smaller the particulate being removed the more time. The warmer the fluid, the easier to pump.

vtfarmer

@Jamie Hall I've run some pretty dirty oil through all sorts of injection pumps and injectors and been lucky - usually they fail in such a way that they don't crack at consistent pressures anymore or don't completely shut off and end up coking the pre-ignition chamber (so glad I don't run any indirect injected diesels anymore). The injection pumps usually have governor issues before the plungers get hosed. Yes, water will wreck your day pretty quick but I'm quite diligent about that.

You should peruse some of the fuel threads on farming sites - it will make you cringe!

hot_rod

Jamie Hall said:

I might add, @vtfarmer , that if ANY of that dirt gets into the injectors on your equipment, they're toast. If it's at all hard, it's not very kind to your high pressure pump, either. That's why you have all those filters.

The other problem with reusing oil is the possibility of water contamination, and -- related -- molds and slimes. That's why there is a water separator on your diesel fuel system (I hope) and why you pay attention to it -- on some types of injectors, a slug of water will cause catastrophic damage (if you're lucky, it may not destroy the engine -- just the injector). The related molds and slimes will just clog the filters quickly, which results in silence...

I learned that exact lesson with some recycled diesel in my John Deere tractor, cost over a grand to have the injector pump rebuilt. Removed the fuel tank and flushed lines and fuel pump. What a messy repair to save a few bucks! It took it out the injector pump in a few hours run time. Sediment and water, silica the size of toothpaste is all it takes.

Jamie Hall

Oh I do peruse them! And they are just frightening! We're farmers and loggers, too, and diesels of various sizes are part of life...

vtfarmer

I love measuring things empirically: testing soils, tracking yields, having a bluetooth gauge set and micron vacuum gauge for refrigeration work, and yes when I used to actually live in VT I had an ancient Dwyer CO2 and smoke measurement setup for tuning oil burners (which was almost useless, but didn't end up mattering given I heated 95% with wood).

Is anyone aware of a tool one could find used but serviceable on say, eBay, to measure how much contamination from suspended solids there is in a given fuel sample? I suspect something like this would be expensive to buy new.

Dave Carpentier

Years ago, the common trick for heating oil tanks was to angle the tank so that settled foreign stuff would stay in the tank instead of draining out the bottom port on the end and into your equipment. In an ideal world, this sludge would be removed routinely but of course it wasnt and would help rot the tank out.
So code install became to tip the tank towards the outlet and drain any settled stuff out into your equipment.
A sludge port at the bottom end and an equipment port on the end face but an inch or two high up the end wall would have been handy.

Robert_25

I would not hesitate to put the filtered oil into another heating oil tank, but never into the bulk tank for equipment. We did a large job down in VT one time and ended up getting some fuel from the farmer to get through until the equipment was close enough to the road for a bulk delivery. We had a few cold mornings and could barely get the equipment to start. Turns out the farmer was buying reclaimed fuel from some local outfit. In addition to concerns with dirt and water, the fuel clearly did not meet the cetane requirements of diesel fuel. Once we got back to fresh diesel the starting problems went away, despite the weather continuing to get colder. We mentioned this to the farmer, but they preferred to stick with what they were doing, which included using block heaters in October.

STEVEusaPA

Thanks for showing that visually to people. Whether they heed your advice is anyone's guess.
The only way to re-use that fuel is to put it through a fuel polisher. Good generator companies do it all the time for their customers generators-where fuel can sit for long periods of time. Almost no amount of filtering would make it clean again. At least not to the point where your filtering costs are outweighing the fuel cost.
I always recommend selling it or giving it to someone who has a waste oil burner. Otherwise it just causes problems. Which is why most tank manufacturer's void a warranty for used oil into their tanks. Or to think of this way, you took the oil out of a 30 year old tank. Why do you want to give your new tank a 30 year head start on corrosion with all that crap in your new tank.
Europe and other countries have companies that clean their tanks/polish their fuel as a regular interval maintenance item.


--Boring true life story--
Have 2 customers-a father and a daughter. Father has a plumber switching him to gas. I tell him all the above about transferring that oil to his daughters tank. He's told by the plumber how I'm wrong, I just want to sell them new oil, plumber does this all the time with 'no problems', etc., etc.
He transfer the oil to his daughters house, filtering it like the OP above did.
It took years to stop the plugged filter/plugged strainer/plugged nozzle calls. It got so bad after the first season and a half that I taught the son-in-law (car mechanic) how to change the nozzle/filter/strainer and bleed the fuel pump. Sold him a bunch of them.
The only help in mitigating this problem was whenever I came for a delivery (with additive), I had him/her turn the burner switch off for an hour.
Finally got better after about 5 years.
Look at all the money they saved!

jumper

Cleaning & drying diesel/heatingfuel is relatively easy.

leonz

A two micron Racor fuel filter in a RACOR FG500 filter housing does wonders by spinning the fuel through it as it passes through it.

The water and the dirt and other crap falls out to be drained out by the manual drain as the fuel passes up through the 2 micron filter.

Jamie Hall

How fussy one needs to be about the fuel quality depends almost entirely on the equipment you are using it in, and the potential downsides. For example, burning it in a heating boiler really has a very small downside. The worst that can happen is that either your primary filter clogs, your nozzle or its screen clogs, or in the very worst case the pump is damaged (amazing what a few flakes of rust can do to close tolerance gears). In any case, no big deal. You get cold for a few hours or at worst a few days. A process boiler might be a little different -- but you might have two, or at least have someone on staff or very handy who could get it going quickly.

A diesel engine is another matter entirely. Even a relatively simple breakdown -- a plugged or jammed injector -- may only mean a grand or so in towing charges if you are close to a road (if you are a mile up in the woods... or out in the middle of the back 40 -- it can rapidly get more impressive). More serious damage, say to a high pressure fuel pump (and some diesels may run the high pressure rail at upwards of several thousand psi) can cost a wee bit more. And truly catastrophic damage -- say from a jammed open injjector fluid locking a cylinder -- can cost you a new engine; not a very enchanting thought.

So it depends. What are you using the stuff for? What are the potential problems which might arise? What are the consequences?

And of course all this assumes that the old fuel still meets the specifications of #2 fuel oil...