What brand of gear oil would you recommend for my Toyota with 100K miles on the trans?

By gear oil I am going to assume you mean automatic transmission fluid. I am not aware of any differences between the brands. But, I am wondering why you need it. If you have a leak, consider an additive that swells the gaskets and seals to reduce or even eliminate the leak. If you are planning to change the transmission fluid, be aware that Toyota says that under normal conditions, there is no reason to change it. It does not wear out. If it looks very dark and smells burned, due to having towed something huge or getting stuck in the snow, then change it. Otherwise it is just a waste of money. If you mean gear oil as in manual transmission, again brand is not an issue and just use any appropriate weight gear oil (80W or 90W, check the manual).What brand of gear oil would you recommend for my Toyota with 100K miles on the trans?
For a car with 100k on it, I'd recommend switching to a good synthetic gear oil (manual transmissions only) such as Redline, Mobil 1 or Royal Purple. The consumer type stuff form Castrol and Valvoline would be OK too, but it just isn't the same quality as Redline and Mobil 1





For an automatic transmission, any higher-mileage ATF would do quite well. And contrary to what was said before, it's not the oil that wears out, it is the additive package that wears out. This is why car manufacturers recommend changing it out at set intervals, stated in your owner manual. Most are usually 30k or 60k, depends on the manufacturer's care guidelines.