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

Just bough that exact one last month. Look online they had a 20% off coupon

I don't know how old mine is, but It cranked just fine even during the recent cold snaps of -30 C. I'll check it sometime, probably in the spring, since it's too $@% cold to work on the car outside. Oh, what I wouldn't give for a few solar flares.

Replace it proactively is my vote!

When you do replace it select a battery in AGM chemistry.

Better temp resistance, vibration resistance. Slower discharge rate and faster recharge rates are all benefits of AGM technology.

By 2016 over 50% of all domestic auto manufacturers will ship their models with AGM batteries.

FWIW I work for the largest battery retailer in the nation.

I work with Bonnie the head of distribution @ (EMP) East Penn Manufacturing AKA DEKA they are the largest manufacturer of car batteries in the US and make an excellent product. They produce the Duracell Procell Flooded and AGM product for us and we are having excellent results and very few warranty claims.

I personally run the ODYSSEY AGM product in all my cars as they have proprietary manufacturing techniques and use virgin lead Vs. Recycled which will produce more CCA's and a longer service life overall.

I run a lot of aftermarket Audio and Video in my cars so I like the extra power the ODYSEEY provides but for daily drivers and W/ Audio under 1000W the Procell AGM will work great!

Group 49 is the most common for our application but most BMW's will accept a 94 or 95 size as well depending on the mounting location and number of screw points for the hold down cleat.

Helpful Tip - After replacing your battery the 4x4 DSC light may be on.
Turn the wheel all the way to full lock right and then back to full lock left. the will calabrate the steering angle senor and the light will go out.

I deal with east penn batteries on a weekly basis maybe I could get a good deal from them this summer when I`m going to replace my battery.