General Question

LuckyGuy's avatar

Does home heating oil settle, fractionate, or deteriorate if it sits in the tanks for years?

Asked by LuckyGuy (41677points) January 29th, 2016

I live in the Northeast and mostly heat my home with free wood from my property. The house is equipped with a ~10 year old oil fired, hot water baseboard system. I have two 275 gallon, (1000 liter), oil storage tanks in the basement that stays at a relatively constant 56F, 13–15C all year.
I only turn on one tank at a time and my furnace only runs when I am lazy (cold mornings) or traveling.
Since I use wood, the oil in my tanks can, and often does, sit for years. On average, I might go through one tank per year. When one tank gets near empty, I switch over to the other tank and order a load when the price is low, usually in the summer.
A “normal” house only has one tank, burns 1000 gallons, 3800 liters, and gets oil delivered about 10 times per heating season. The oil is always “fresh”. Obviously, my usage is not normal.

Is there any disadvantage to running this way? Is the oil breaking down? Is there data that shows how/if oil changes over time? I have “googled it” already and only see information from sources that want to sell magic elixirs that are “guaranteed to take inches off my wast, make me hard, and increase my bra size.” I can’t find a reputable source that answers this question.

I have not noticed any problems and my filters and nozzle are always relatively clean. I’m just wondering if there is any disadvantage to using old oil.

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7 Answers

kritiper's avatar

No, but there could be some rust from condensation (as well as condensation) sitting at the bottom of the tank. If in doubt, install an in-line oil filter. (A primary fuel filter for a Diesel engine is cotton wound to absorb water.)

Tropical_Willie's avatar

^^^^ What @kritiper said ! ^^^^

LuckyGuy's avatar

I have shutoffs and cartridge filters at each tank. Just before the pump I have another cartridge filter and a Tiger loop debubbler with a clear glass inspection port.. The oil always looks immaculate – even if it is 4 years old.

The price of oil has dropped so much it is ⅓ of the price it was about 2 years ago. I am (shudder) thinking of using the furnace a little more – almost like a “normal” person. But then I’d have to get rid of junk wood another way.

Buttonstc's avatar

You’ve seen the movie, Fargo, right?

Just rent a wood chipper. It would make good mulch?

LuckyGuy's avatar

@Buttonstc I have so much wood. I can go through 15 face cords in a season and I am still over a year ahead. Plus we have bonfires regularly.
And every few weeks another tree bites the dust. My chainsaws get a workout.

That is why the oil tanks stay full for so long.

CWOTUS's avatar

I don’t know about home heating oil, but it reminds me of a funny incident from my youth …

We lived on a lake in the summer time, and I was always in or on boats there all summer long. I was either canoeing, rowing and exploring, or fishing, or later in my youth, sailing – and then only sailing. But I had always wanted an outboard motor to put on the rowboat to make it easier to go farther from home and fish in areas I didn’t care to row to and from. So one day out of the blue one of my father’s cousins offered him an ancient (even at the time!) Evinrude 1.5 horse outboard. It had an integral fuel tank, and being a two-stroke product of its time, it required oil to be mixed in the fuel with every fill-up.

The thing had not been run in years, perhaps decades, and it wouldn’t run when it was given to us. But it still had fuel in the tank! Dad agreed to take it, and he put it into the truck to bring it to our permanent home to strip it down, clean it up and reassemble it. That afternoon, while driving home and in the middle of nowhere (literally, just outside of Podunk, Massachusetts, which is a real place) we ran out of gas. In another first (since Dad never ran out of gas while driving) he also didn’t have a can of fuel with him. But he did have a funnel, and we had that old Evinrude, and it did have some fuel in it, so …

I held the funnel while he opened the fuel tank and upended the motor to pour its tank’s contents through the funnel and into the truck’s tank. That fuel didn’t pour, it sort of oozed. It had the color and consistency of thick, brown molasses – and this was a reasonably warm fall afternoon. It took several minutes to pour the equivalent of, I suppose, a cup to a pint of “fuel” into his truck’s gas tank inlet.

We closed everything back up, and put the outboard back in the truck. He turned the key to crank the truck engine for a bit, and it started up. It ran rough and smoky as all get-out, but it ran several miles to a farm that he knew of, where the owner, another friend of his, gave us a few gallons of “actual gasoline” that got us back to the road again for a proper fill-up at a service station.

I don’t know the chemistry about what happens to gasoline-oil mixtures that are left alone for a long time. I don’t know if the gasoline in that tank had undergone more than just evaporation, or whether it was en route to some kind of phase change, or what. But I thought you’d enjoy the story, anyway.

I’ve got another story about the time I accidentally filled my boss’s gas-powered pickup with diesel fuel, but that one wasn’t so funny at the time.

LuckyGuy's avatar

@CWOTUS Nice. Gasoline is a collection of hundreds (maybe thousands) of organic and inorganic compounds. The mix is intentionally varied several times per year to provide quick starting and smooth operation in cold weather and a slower evaporation rate in hot weather. Summer fuel has a lower RVP, Reid Vapor Pressure, than winter fuel. It has fewer light ends and will not evaporate as quickly when subjected to heat. Winter fuel has a high RVP and is great for starting a car in cold weather but it will eventually evaporate and turn into summer fuel when it is subjected to heat for a long time.
Gasoline engines are quite forgiving once they are started. If you have even a little “normal” gasoline and mix in the oily residue of old gasoline as long as the stuff can pass through the fuel filter it will work.
Here’s another trick. The fuel pickup for most vehicles sits near the bottom of the fuel tank and is covered with a sock-like filter. It can never be right on the bottom of the tank. When the fuel level drops below the pickup, the fuel flow stops and you are out of gas – even though there still is some in the tank. If you were able to pour a little liquid with a higher density than gasoline into the tank it will make the gasoline rise to reach the pickup and you can drive. Eureka! Ideally you pick a liquid that is soluble in fresh gasoline. Old, evaporated gasoline is perfect!

By the way, my Tahoe with its 24 gallon tank gets fed all the old gasoline from my mowers and tractors when I empty them or take them out of storage. I do not throw out gasoline no matter how old it is.

I’m guessing the RVP of oil must be so low there is virtually no evaporation so 4 year old oil is just as good as fresh oil. It certainly appears to be.

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