# Used Vegetable Oil
**URL:** https://boards.straightdope.com/t/used-vegetable-oil/291107
**Category:** Factual Questions
**Created:** [February 21, 2005, 3:35am UTC](https://boards.straightdope.com/t/used-vegetable-oil/291107 "2005-02-21T03:35:00Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Junior\_Spaceman](https://boards.straightdope.com/u/Junior_Spaceman)
#### Post date: [February 21, 2005, 3:35am UTC](https://boards.straightdope.com/t/used-vegetable-oil/291107/1 "2005-02-21T03:35:00Z")
What can I do with vegetable oil after it’s been used once?
I’ve deep skillet fried chicken with a substantial amount of oil for frying. I’ve now strained it and kept it in a metal bowl. It seems a shame to dispose of this oil immediately, without using it again.
Can this oil be used more than once?
If so, how do I “keep it” until further use?
If not (or even after it’s second use) how can I dispose of it properly?
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### Author:  [@Nametag](https://boards.straightdope.com/u/Nametag)
#### Post date: [February 21, 2005, 3:51am UTC](https://boards.straightdope.com/t/used-vegetable-oil/291107/2 "2005-02-21T03:51:55Z")
Yes, you can keep using frying oil until it smokes. Let it cool and put in an old oil bottle. Disposal: do the same, and throw it in the trash.
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### Author:  [@ouryL](https://boards.straightdope.com/u/ouryL)
#### Post date: [February 21, 2005, 8:31am UTC](https://boards.straightdope.com/t/used-vegetable-oil/291107/3 "2005-02-21T08:31:53Z")
My mommies rule is twice then toss. Especially if you cook more than one batch. Even then, add new oil. 😛
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### Author:  [@EvilGhandi](https://boards.straightdope.com/u/EvilGhandi)
#### Post date: [February 21, 2005, 8:41am UTC](https://boards.straightdope.com/t/used-vegetable-oil/291107/4 "2005-02-21T08:41:33Z")
I hate the smell of used oil, yet loves me the fried foods. I dump it the minitue I am done with it.
I wish there was a place that (remnicient of WWII) wanted our oil to blast the Japs. or something. I wouldn’t care if they didn’t blast anyone. I do plumbing and I know what kind of crap my dumped oil causes.
So what is the dope? I know we have a few chemical engineers onboard here. Is it too expensive to collect this potential fuel than it is worth? I imagine used fryer oil would be MUCH cheaper to refine than say, drink boxes, or even bottles.
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### Author:  [@KP](https://boards.straightdope.com/u/KP)
#### Post date: [February 21, 2005, 8:58am UTC](https://boards.straightdope.com/t/used-vegetable-oil/291107/5 "2005-02-21T08:58:04Z")
Lightly used, properly stored oils can be re-used many times. Restaurants (which hardly qualify as light use) often only change it once or twice a week --dozens or hundres of uses. Oxidation, water contamination and “burned bits” all contribute to oil degradation. I find that allowing it to cool, then filtering it into a jar through filter paper is enough. The instructions for many deep fryers say it can be stored in the fryer for a 3-4 weeks in cooler climes, and you _know_ that they are going to be conservative – they have nothing but liability to motivate them. The type of oil and deep fryer is also very important. many deep fryers and a cool trap under the heating coil which can greatly extend oil life by trapping burned bits and moisture.
This isn’t medical advice. It’s barely even English.
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### Author:  [@InvidiousCourgette](https://boards.straightdope.com/u/InvidiousCourgette)
#### Post date: [February 21, 2005, 9:32am UTC](https://boards.straightdope.com/t/used-vegetable-oil/291107/6 "2005-02-21T09:32:52Z")
> [@EvilGhandi](#):
>
> So what is the dope? I know we have a few chemical engineers onboard here. Is it too expensive to collect this potential fuel than it is worth? I imagine used fryer oil would be MUCH cheaper to refine than say, drink boxes, or even bottles.
Cheaper indeed. At its simplest you can do this:
1. Filter your oil through a cloth
2. Add a spoonful of methanol
3. Use resultant mixture as fuel in your diesel car
The car program Top Gear did this a few years ago with a Volvo, after first emptying it of real diesel fuel. It worked fine. I would not recommend going down this route, however. In the long run it will likely foul up your engine. It is quite possible, however, to be a bit more sophisticated and you will be able to run a diesel vehicle just fine on used cooking oil. It makes most sense if you have access to a business that produces a lot of the stuff. Collecting domestic used oil would probably be uneconomic.