You should be OK without a heater. You may want to change all your oils to synthetics.
AMSOIL Series 2000 Synthetic 0W-30 Motor Oil is specially formulated for superior cold temperature engine protection. Series 2000 retains excellent fluidity in extremely low temperatures, so it flows quickly and reliably to allow easy starting and immediate lubricating protection.
AMSOIL SEVERE GEAR EP lubricants excel in hot and cold temperature extremes. By design, they resist breakdown from high heat, preventing acids and carbon/varnish formation. Their waxfree construction also improves cold flow properties, improving fuel economy and cold weather shifting.
Koz