I also had to replace the battery on my 2003 mazda 6. Now They tell me my engine has died and my catalytic converter broke into pieces. They estimated the job at almost $7000. When the problem first started the car would not accelerate from a steady speed on the highway, it would loose all power and then it started stalling! I have the extended warranty up to 100,000 miles and when I brought it to a mazda dealer when I first had a problem it was at 99,000 miles. Now the car finally died completely and of course now Im over 100,000 miles and they don't want to cover it! I am going to arbitration on my warranty! I changed the oil every 3-5 thousand miles with synthetic oil. They mechanic thought I had added oil to the car because the oil was so clean, but I never had to add oil. I towed the car to my mechanic because I am done with the Mazda dealer, I bought it brand new, and it has an engine that died when I took care of it! Anyone who has any suggestions or a similar problem send me a message