I've never used it, but I agree that ATF+4 is a good fluid and is a synthetic. However, I'm pretty sure that it does have different friction modifiers in it due to use with modern computer controlled transmissions. In other words, the shifts may not be as crisp/hard as it would be with Type F or other race related trans fluids. But it obviously works well in most applications. Synthetics are a big plus since they are more resistant to breakdown from heat. I use Amsoil Super Shift.