Used motor oil on treated pine

Question

I am having a large bin made for refuse bags at our beach house. It will be made from treated pine and stainless steel screws and hinges. I was quoted for the job which includes 4-5 layers of used car oil to treat the wood (probably for cost saving as well as longevity).

I am not concerned about the look, but rather whether this is inferior treatment to another treatment option that is still affordable and won't require more maintenance over the coming years.

My other concern is the environmental impact. Will the oil leak in any way once absorbed into the wood?

I live in South Africa.

Answer 1

Depending on where you live, this may not even be legal. Used motor oil, where I live, must be collected in leak-proof containers and periodically picked up and taken to a depot where it is reprocessed. Using it as a hack outdoor finish is not legal here, and rightly so.

Everything that is in the oil and inside the engine of a car (aromatic hydrocarbons, volatiles, heavy metals) will end up in your local environment over time.

If we were living in a time where good outdoor finishes weren't easily found, or were too expensive, you might see motor oil as a poor last choice. At some point all kinds of petroleum products were used in this manner. For example, it was common for diesel fuel to be put to all sorts of uses when it was cheaper and easier to come by (and the cheaper stuff wasn't dyed red) than alternatives. Many of us are living in houses where the basement was sprayed with petrochemicals as part of the concrete pour. You aren't allowed to do that anymore.

It just makes no sense today. It'll make a terrible finish and to add insult you will have to reapply regularly.

This whole idea is so astonishing in 2021 that I'm wondering if the wood whisperer you know doing this has ever actually used the internet, or even read a booklet on finishing outdoor projects from the last three decades.

Please, just skip this and use one of the good outdoor penetrating finishes and commit to splashing on more coats semi-regularly, or go for a sealing product that'll last years between reapplications.

Modern finishes are so much better than this worst, last choice.

Answer 2

but rather whether this is inferior treatment to another treatment option that is still affordable and won't require more maintenance over the coming years.

It's certainly something that people do -- you can find lots of people discussing it if you search for something like "wood motor oil." I've never tried it myself, and I wouldn't do it. A proper water/weather sealer for wood costs about $20/gal at any home center. Using motor oil to seal wood makes about as much sense as using wood sealer to lubricate your engine.

A good deck stain would be another option, especially if you'd like to choose the color.

My other concern is the environmental impact. Will the oil leak in any way once absorbed into the wood?

It surely won't leak out in the sense of dripping on the ground, but everything that's in the oil will eventually end up in the environment somehow. No wood protectant lasts forever; some of that oil may soak into the wood and stay there, but only until you eventually replace the bin, and at that point it'll end up in the landfill or incinerator. Some of it will leave the wood through weathering and end up in the soil or water.

Answer 3

You don't say where beach house is, maybe in California? 100% this is illegal there :)

Used motor oil provides long service for untreated wood used as posts set in soil. Usually only used on farms and other rural settings.

It gives v good protection but ends must be soaked in oil for a long time to be effective.

• end grain is like a sponge, soaks in oil deep

For side surfaces wood must be dry or treatment will be ineffective.

• treated wood sold wet in America

• oil / water do not mix

Treated pine already has 10+ year lifespan with no maintenance. Do maintenance and it maybe lasts until you don't need it any more!

If you want zero maintenance option pay more now, less over time. Have bin made from:

• white oak
• redwood
• western red cedar
• catalpa
• Pacific yew

Bin will look better, less cracks and splits, because these species are not sold wet.

Bin will last longer. White oak survives outdoors with no maintenance for 30+ years in wet setting, 100+ years in dry setting. Durability of other species on list equal or higher than white oak.

Answer 4

I'm not sure about using motor oil for a garbage bin? I'm having a hard time getting my head wrapped around this? Is it like an enclosure around a dumpster to keep animals out?

Regardless a mix of used motor oil and diesel fuel (I can't remember the ratio I was actually trying to find that when I stumbled across this post.) I think it was 2 parts diesel to 5 used oil, I remember I tried 50/50 first and the uptake wasn't consistent so it's not 50/50.

Anyway old oil & diesel are the best solution I've found in two specific instances.

1. Is if you are cementing untreated beams into the ground. The stuff is amazing. I have a large shed/hangar for my ultralight where I framed out the doors and support beams from regular old Douglas Fir studs soaked in the stuff for a couple days and it has over the past 15 years held up to scorching temperatures 120F+, monsoon storms, at least 2 microbursts, and took it all like a champ. I've had the roof come all the way off once and partway off another time. If there were ever a tornado or hurricane here (very unlikely in AZ) it'd be a tossup which I'd try riding it out in the shed or the house.

2. Is where you are looking for insect resistance. Ants and termites give it a wide berth, and I've seen scorpions literally everywhere else on the property besides in and around that shed. Yes that includes in the house.

Unless your use case involves one of those two scenarios you're probably better off with another product. Oh yeah and if you do ever use this stuff make darn sure you wash your hands with Dawn dish soap before eating anything. I made myself violently ill twice building that shed before I caught on to what happened to me.