Man the 6 loves to eat batteries.....
 

OEM battery made it barely 31,000 mi. Sears silver replacement made it 36,000. AND died TEN DAYS out of full replacement.

Surprising to see on other Mazda boards just how quickly the 6 goes through batteries. The lack of airflow in the mounting location must have something to do with it.

mine only lasted 3 years and 40 k maybe? I swore it was a differnt problem becuase I couldn't believe the battery would go so quick. I've had 8+ yerars in my other cars ( I know that's longer than usual)

I have had the same battery in there since 2005. I had the fan control module replaced right before the last one went dead and have seen no problems out of this one at all. (knock on wood). I think that the bad fan modules drain the battery after the car is turned off and the altenator cannot charge it back up.

Heat kills the batteries, but you don't notice it until you need it in the winter time.
The location, (mine is by firewall) is high and it still gets quite a bit of heat from the rad and engine.

When it's dead, it's dead. Both of mine gave-up in the middle of summer.

Is Interstate battery best for mazda6 or not? I had replaced 3 batteries during first 63,000 miles.

I don't have any battery over 36,000 miles in my mazda6.

The ground wires need cleaning once in a while---especially main one @ body. good idea to put a few more as well (another body, engine block, throttle body, tranny). Electrically it will be better. It may even help battery.

A ground isn't going to help the battery live longer. If the battery was insufficiently grounded, it would present itself due to sensors not carrying and subsequently reporting sufficient voltage back to the ECU.

Yes, you can add additional grounds from the engine to the chassis. In fact, this was a problem with Duratec engines; insufficient grounding causing electrolysis in the cooling system, leading to early break-down of the coolant and cooling system components.

When I installed Weapon-X coils, they suggest adding grounds. I added one from the engine mount to the body just next to the brake lines (pics attached) - one from the engine to the chassis under the throttle body - and one from the throttle body to the battery hold-down.

Like I said before, heat kills these batteries but you don't realize until it gets colder when your CCA goes down. Read #5 and #9 of: http://autorepair.about.com/library/.../aa101604g.htm I went out New Years Eve. It was the first cold night last night below -20. Today Jan 3 tried to start car, battery turned for 2 secs at a slow state then just clicking and died. I bought it Sept 8, 2009. It's a Yello Optima. The guy said these batteries are good in heat. That may be true, but they suck under -20! He gave me a temporary new battery, he said my old battery was borderline, he's going to re-charge it overnight then load test it in morning. I'll be seeing him tomorrow afternoon. What a way to start off the New Year: jumping my battery out in the cold! It's obvious my extra grounds didn't really help, but they are required with the aftermarket sub amp.

I have seen a car with an air supply to the battery tray. Do your 6's have that?