How long is vegetable oil good for?

My wife is using some old oil in some brownies, I'd say at least a couple of years old, is it going to be harmful in any way? There is no expiration date on the bottle so she says it never goes bad. I don't know.How long is vegetable oil good for?
in my opinion vegetable oil isnt very good tasteing to use. the oil flavor is too strong if your bakeing use real butter.its much better tasteing.but vegetable oil will last a good while.i dont keep mine around more then 5or6 months but im sure it last longer then that but the longer it sits the stronger the taste gets and trust me you dont want to taste it when it gets real strong.:)How long is vegetable oil good for?
I think it have an indefinite self life. If, you strain and reuse it good until it burned or take on the tastes of what you fry. I use oil separate for Fish, Onions and other foods. Peanut oil best for High temperature frying as it not burn as quickly. Canola oil I use for medium Temp. Olive oil I use for low temp.
Smell the oil...


If it smells rancid, throw it out...


Oxygen %26amp; Heat makes oil go rancid..


Store oil in fridge to extend its lifetime...