I just changed mine this week using Valvoline
Synthetic DOT 3&4. My research revealed DOT 3, 4 & 5.1 were my choices with each having both a higher dry and wet boiling point as the number increased. Also, DOT 5.0 is silicon based and not compatible with the other 3. In fact, my SPF manual recommended against using 5.0. I couldn't readily find 5.1 locally, so I used the highest boiling point product I could find here without ordering it.