How large is the new pile? If the new pile is large and the cooking oil would make up a small percentage of the pile, it should be ok. Make sure to mix it throughout the pile and not have it all concentrated in one spot.

Cooking oils are fats and fats give the bacteria that digest the material in compost indigestion. It is not a good idea to add large, and this is, amounts of fats to your compost.

Hmmm, well my pile is about 3x3 wide and about 2 feet high. Maybe I could include some rolaids?

I would add it, but maybe add it a little at a time so you don't overwhelm the pile.

Cornell University, the Rodale Institute, the Master Composter, and many other sources of good, solid composting information do not recommend adding fats to compost.

I have BIG compost piles - thanks to the ice storm and local tree timmers one is approx. 20'x15'x5' and gets turned with the tractor ;) and like kimmsr I avoid adding fats/oils. But that is because I hope to use it all up in my lifetime.

In any quantity, they can shut a pile down completely. But in your small pile, if composting time is no object and you have a steady source of other really good additives for your children and grandchildren to add go for it. ;)

Seriously, instead use it to kill weeds in the gravel drive or in the cracks on the cement patio. Leave it out of the compost pile.

A couple cups would be fine. 2 quarts is a lot to add to that pile- and I'm the guy that always says "go ahead- throw it in!".

I fail to see why adding fats would kill the pile...
Of course I drive a diesel car so I'd probably strain it good and run it...
Seriously though it came from vegetables, it'll compost. I probably wouldn't dump it all in at once but maybe a cup a week, it'll be gone in no time.

Ever accidentally spill motor oil? It takes a while but the ground recovers...

It won't kill the pile- it makes it smell and will slow it down a great deal. It coats everything, smothering some of the microbes, and creating a small anaerobic region as well (oxygen doesn't dissolve well in oil). Yes, it is in vegetables, but in a very dilute form. There' gold in seawater as well...

Well, that's my guess. Anyway- whether I'm right or wrong on why it happens- I've seen that it does happen.

I do like the idea of using it to kill weeds!

I really want to keep from having to take the oil to the landfill and would love to make use of it here.

I appreciate all the input and understand why some would or would not add it to a pile.

As for killing weeds, do you just pour a little on to smother the weed? I have a short gravel trail leading to the woods that I constantly weed. Will the vegee oil attract racoons? I have already had one destructive visit after having left cat food on my deck!!

I see coon skin hats for sale in my future!