3-in-1 is pretty unpleasant, I agree. I use it as a cutting fluid for drilling steel mostly and it's not any nicer when hot. Perhaps I will try some of your gun oil.
Best smelling shop liquid I've yet encountered is Marvel Mystery Oil. It's amazing.
Pluses and minuses as cutting fluid. It's not sulfurized or chlorinated, like actual (and lower cost) cutting fluid. On the other hand, the vapors are non-toxic, being mostly polyalphaolefin synthetic oil, and it likely is better than 3-in-1 as cutting fluid for adhoc use, if only due to significantly lower vapor pressure and higher flash point.
topspin|1 month ago