I believe diesel engines require a heck of a lot of cold cranking current...so it's a more powerful battery. Probably nice to have if you live where temps are extreme, or you're running a stereo with a dozen 18-inch subs!

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car