What is the high ba? I used test500 last winter and I didn't get any sorta pain from it. But yes, sterile oil will be fine. I'd be willing to bet even that eq you have will be fine to cut it with...
Yes, which brand is it? If you got a brand from someone who at least half knew what he was doing, it shouldn't hurt much. I've made 500mg/ml test enth and cyp and both were painless. Then again, if he just went the ole 10%BA route like Denkall's T400, then yeah, you're in for a world of hurt