Depending how long it's been sitting (and it's propensity to wet sump), I wouldn't go more than half full to start. Then run it, making sure oil is returning to the tank. When it's up to normal running temperature, top off. Oil expands quite a bit when warmed up (or maybe it's just frothing) and if you fill the tank cold, it will definitely puke all over the place when it warms up.
