Maintenance Items

Happy Holidays To All!
Recently we have been receiving alot of skepticism from our customers regarding certain items that we recommend as part of our 30,000 mile scheduled maintenance packages, such as the transmission fluid and coolant change at 30,000 miles. Our carline (High-line Asian) only specifies an "Inspection" of the coolant and trans fluid at 30,000 miles. We are in Houston where the driving conditions are brutal and leaving coolant/tranny fluid in for 60K miles is asking for trouble. The vehicles are not equipped from the factory with extended life fluids. Does anyone out there know of any websites where I can get some technical data to back up our recommendations? Any other suggestions?
Thanks,
Mark W. Bailey
Recently we have been receiving alot of skepticism from our customers regarding certain items that we recommend as part of our 30,000 mile scheduled maintenance packages, such as the transmission fluid and coolant change at 30,000 miles. Our carline (High-line Asian) only specifies an "Inspection" of the coolant and trans fluid at 30,000 miles. We are in Houston where the driving conditions are brutal and leaving coolant/tranny fluid in for 60K miles is asking for trouble. The vehicles are not equipped from the factory with extended life fluids. Does anyone out there know of any websites where I can get some technical data to back up our recommendations? Any other suggestions?
Thanks,
Mark W. Bailey