Thanks Grant, I did not consider that the 40 is less resilient at typical track temps. I still don't think the 5 weight is needed for summer since these engines warm up fast and they are already at ambient temp. I have been changing my oil before and after the track plus a week on the street so I will look around for a good deal for some 10w50 or 15w50 for the track and stick with the 40 for the street and AutoX. Glad we had this thread pop up.