We are considering using Petro-Canada semi-synthetic ATF in a fleet of Crown Victoria police cars, at extend fluid change intervals. We have been using a full synthetic (Protec), with a complete flush at 25K and then again every 100K. We have had good results with this program and experienced a reduction in transmission failures and down time. We are looking at other alternatives for ATF. Up to this point cost hasn't been as much a factor as availibility with Protec. Has anyone had any experience with P-C semi-syn ATF in an extended service program.