Anyways, yes, Champ Car, not Lemons. I believe any external oil cooler would incur the penalty, yes, even a factory style. We are already starting at a 5 lap disadvantage, and we have to take another lap or two for other "mandatory" changes (driveshafts on these cars tend to come apart over 120 MPH or so and we may take a penalty for an adjustable panhard bar just to get the rear axle positioned back after lowering). We heavily considered using the factory AC evaporator and trying to fly it under the radar just in case...but we decided it wasn't the risk of it running into the cabin and trying to leakproof it.
I took a glance at the champcar rules shortly after reading this thread and I think you are right. It says "non-OE". On one hand in my mind that leaves it fairly open to interpretation for ideas like Vermeers with OE internal radiator trans coolers etc, but I'm sure if a tech sees oil lines going from a filter block to the radiator they might disagree, lol. Maybe subtly ask some guys who have had their cars tech'ed at these races before to get an idea of how stringent it is.