Bamby, if you don't mind doing a little research I think there is a simple solution for you. There is a clay (bentonite) grease that is readily available in Australia, called Castrol HTB (which stands for High Temperature Bearing). It is intended for use in the front hubs of vehicles with disk brakes, so it does not melt and doesn't even become mobile in the hub under considerable heat. I have read on the net that the reason for Peerless/Tecumseh recommending a bentonite grease is that they are concerned to have a very thick, non-slumping grease even at high temperatures, and they also want water resistance, and HTB should provide both of these properties. If you can compare the basic viscosity (stiffness) of HTB with your old grease at room temperature, and if they are about the same, you should be good to go with the HTB.
