electronically, some computer program "sees" the order and takes an action before it, that moves the price by a penny or a fraction of a penny. I used to think I got a fair fill at the bid or ask price (depending whether I was short or long), but they can actually front-run you in a sub-penny way. In other words, you don't even notice it at the bid/ask prices.
I didnt know you could get filled sub penny on CL. I though that was only going on in stock fills. Do you have more info on this?
you sure your software isnt just showing an average fill price for several entries? 4 @ 73.07 & 1 @73.08 gives you an avg fill price of 73.072
Minimum Fluctuation $0.01per barrel http://www.cmegroup.com/trading/energy/crude-oil/light-sweet-crude_contract_specifications.html