But on the Ascent tests, the WIX XP (lowest efficiency) showed the highest capacity, lowest differential pressure and the longest time to fill up, while the Royal Purple (second highest efficiency) had the second lowest capacity, highest differential pressure and shortest time to fill up. On the BR test results, the Amsoil, Royal Purple, and Fram Endurance showed among the best efficacies but among the lowest capacities and hot flows, while the Wix XP had among the lowest efficiencies but among the highest hot flows and capacities. The Boss was the only filter that was among the top in all three measures in the BR tests. So other than with the Boss in the BR tests (and to a lesser degree the OG Fram Ultra on the Ascent tests), there does appear to be a tradeoff between efficiency on one hand and capacity, flow, and time to fill up on the other hand.