When we get automatic cars in for service we always check the transmissions for two things. oil color and level. When the color is extremely dark we give the client a quote on the oil, gasket and filter. yes it is expensive but still cheaper than a rebuilt or new gearbox most of the time they accept and we replace everything and they comment afterwards that it feels like the vehicle drives better. We also only buy the recommended oils for the appropriate manufacturer and parts directly from the dealership. Only original parts. We don't believe in using aftermarket parts or oil when it comes to automatic gearboxes. They scare us🤣. Also had a couple of ramblings at work about toyota and ford saying it is filled for life. what's the lifetime suppose to be then. 5 years tops? it's ridiculous. sorry started randomly rambling. Singing off now before i continue.