Burning down the house (or not).

June 24, 2011 3:20 AM

In a pinch, is it possible to use diesel fuel to fire a boiler that normally runs on no. 2 heating oil?

Three weeks from now, I'll be replacing my oil-fired boiler with a modern, environmentally friendly (er, friendlier) propane unit. Since the clock is ticking on my old, oil-fired boiler, I've allowed the heating oil in my tank to run down to an unthinkably low level. I'm not sure how much remains, due to a flaky meter, but it's in the range of a few gallons or so.

We're in the summer months, so my oil usage is small, but I nevertheless rely on it to heat my domestic hot water. There's a possibility I might run dry before the propane conversion begins. Unfortunately, the oil company sells heating oil in quantities of 50 gallons or more. Making a purchase now would leave me with 40 gallons or more of expensive oil--and an expensive disposal when I remove the oil tank several years from now.

Then, it struck me: why not buy a few gallons of diesel oil at the gas station, and use this instead? Ordinarily, I'd be hesitant to use an unrecommended fuel in my equipment, but the boiler will be junked after the propane unit's in. And according to Wikipedia, No. 2 heating oil is similar in chemical composition to diesel fuel.

Is this stopgap solution a workable one? What would be the consequences of using diesel for the boiler, in terms of efficiency, fumes (if any), and keeping the boiler running for a scant three weeks? Has anybody tried this approach?

posted by Gordion Knott to home & garden (14 answers total)

Looks like you can use diesel.
posted by NordyneDefenceDynamics at 4:00 AM on June 24, 2011 [1 favorite]

Absolutely. They are chemically the same product - diesel fuel is just dyed and taxed differently. (I worked as a manager at an oil company for a few years - if people ran out of oil or were low, we recommended diesel.)

(Diesel will not harm the burner, it will not cause fumes, and it will not make your house burn down. It is just a matter of cost efficiency. Just be careful putting it in - those jerrycans from the gas station are kind of awkward depending on where your fill pipe is!!)
posted by firei at 4:25 AM on June 24, 2011 [1 favorite]

They are chemically the same product

That's not absolutely true, not always at least. Road diesel is generally higher quality and tighter spec than Heating oil No. 2. Diesel has additives for engine use that the heating oil will not.

In short, road diesel is generally a higher quality product than Fuel Oil #2. It can be used just fine as heating oil. Road diesel's main drawback is that's more expensive.
posted by bonehead at 7:10 AM on June 24, 2011

I believe the opposite is true. Home heating oil is dyed while diesel fuel is not. Diesel fuel is taxed while home heating oil is not. I've had inspectors check the color of my fuel in the truck to see if it was dyed. The diesel fuel you buy at the pump has to be clear.
posted by JohnE at 7:24 AM on June 24, 2011

Apologies, gang. Yet another thing my ex-boss lied to us about! But at least we all agree that it won't harm the burner.
posted by firei at 7:50 AM on June 24, 2011

The diesel fuel you buy at the pump has to be clear.

Road diesel is dyed slightly green. Non-road diesel is typically dyed red. It's not uncommon to see state inspectors at farm and ranch events and expos or rodeos testing diesel on the trucks and leaving $500+ fines everywhere for using farm diesel in a road vehicle.
posted by Mister Fabulous at 8:46 AM on June 24, 2011

This is very helpful. I'd been told this before but didn't know if I could trust the information.
posted by theora55 at 9:03 AM on June 24, 2011

And, just to be clear, there is no difference at all chemically between retail and farm (dyed) diesel (at least, not in the testing I've done). That's just a tax thing and a bit of dye.

Diesel colour also has a lot to do with sulphur content. The old low sulphur diesels (LSD) are bright yellow/green from the sulphur compounds. The new ultra-low sulphur diesels (ULSD) are a very pale straw colour.
posted by bonehead at 9:17 AM on June 24, 2011

Yes, this is exactly what my oil supplier (Carson Oil) told me to do when I ran out and they couldn't get to me for 24 hours.
posted by nicktf at 9:31 AM on June 24, 2011

This is basically just like buying a coupe of 30 litre plastic bags of firewood from the local servo for $7 each instead of getting a cubic metre delivered for $50. It's so close to the same product as not to matter.
posted by flabdablet at 9:47 AM on June 24, 2011

Just don't do the reverse and use heating oil in your truck. That's the only proviso I'd make.
posted by bonehead at 9:50 AM on June 24, 2011

bonehead: "Just don't do the reverse and use heating oil in your truck. That's the only proviso I'd make"

It would work ok.

For a while.
posted by ArgentCorvid at 9:52 AM on June 24, 2011

bonehead, for the last 20 years my father-in-law has been running his vehicles on heating oil salvaged from de-commissioned oil tanks. He carefully filters it into wine bottles using coffee filters. Yes, the garage stinks of diesel, but think of the savings!
posted by vespabelle at 10:07 AM on June 24, 2011

The only difference in Diesel #2, and Heating Oil #2 is TAXES. Road diesel has $ 24.4 cents Federal tax + your local state tax added in. The fuel is one and the same. I've sold it now for 37 years in Alaska! We don't dye fuel as a 'marker', in Alaska though...
posted by BVB at 11:00 AM on June 24, 2011