It gets pretty hot there in the summer too! I don't know of any Hypoid gear oil with a lower viscosity rating for that application but maybe check locally and see if it's recommended with that climate. It's not an issue here in San Diego. We want the stuff that will hold up to the heat and abuse we put them through. With 50 years of wear in his 7 1/4, I doubt he'll need to worry about too tight of clearences!