On the stand I'd put a fair amt of (as suggested) ATF in there then turn it over several times to coat the walls etc then turn it upside down/drain it then turn it right side up & at BDC fill it & record the amt then upside down & drain it then right side up & turn to TDC then fill it & record the amt & do the math. Pre coating everything before you calculate will give you significantly more accurate reading I would think because if you dont, the amt left over that is coating the surfaces from the 1st quantity is going to skew the 2nd reading giving you a false reading of more or less CR depending on if you fill @BDC or TDC 1st. How much I do not know but I think w a bit more effort (to precoat) that you can end up w a pretty accurate reading on what you got.