I stuffed the biggest Duralast battery that would fit into my X5, even though it's just the 3.0 engine. With the A/C loads calling for a lot of fan action here in the Texas heat, I want every bit of reserve possible to maintain a steady voltage to the rest of the vehicle. The Duralast seemed to have the best cost/warranty/power for the price as well.

2002 X5 3.0 246,800 miles
2004 325i 109,000 miles