I made a small batch of beaver oil… it turned out great! I am curious do I have to add a preservative to it? Or will it stay fine on the shelf at room temp? How much oil would you recommend to adding to a quart of bait?… just rough estimate to get started!

No preservation needed in my experience. Skip the tail oil in your bait and add the sludge that forms underneath it

Oh Man I already chucked the sludge out!!! That makes good bait also ??

The leftover tail chunks/sludge can be good bait

Tail oil needs no preservatives.

So how much would you suggest I add to a quart of bait to start?? I just want it to be barely noticeable

Ive never added tail oil to bait. I use it as a stand alone lure.
Hopefully some else will chime in. I used the leftovers as a bait by itself. The tail chunks/slurry will catch everything from coyote to possum.

depending on what you are using for your base i would add less then a quart of base to a clean bucket to allow for effortless mixing then to that i would start with 8 oz of tail-oil and whatever other ingredients you think
(Asafetida civet Tonquin or castor) just to give you an idea and you will find when working with tail-oil and castor together one can almost cancel the other somewhat undetectable so keep that in mind and you will have to exsperiment
right everything down then when you are happy with your formula get it down some holes and let the canines tell you what they think of it
and what Turtledale mentioned about the remaining solids after you draw out the oil can make an incredible base for canines

Make sure you write down what your doing.