I replaced the one in my Red Roadster last fall, the Graphite Roadster got a new battery this week (less than two weeks after I brought it home).

Based on the experiences I and others have had with the car not starting/running right only due to a weak battery, I'd suggest replacement at four years.

I got my batteries at O'Reilly Auto Parts, $89.99 last fall and $94.99 this time around. Their charts showed the "Sure Start" model 48-72 as a replacement. It's a bit less tall, so I use a piece of heater hose under the battery clamp to make it fit tight.

Gary (Valkeyryderguy) might be right at 5 years, but I think 4 years is more like it, a battery does not cost that much - yet, we have found several weird problems with these cars are due only to an old battery. Also, if it fails and you need to be towed, you'll spend a lot of money for, what is IMO, no reason.

I say that, by now, all of the original batteries in 04, 05 and 06 cars should have been replaced.


LET ME ADD THIS: Kathy noticed that I often had to try to start my Manual roadster 2 or 3 times. I blamed the fact that it's a manual and does not auto-crank like the auto. But it occured to me yesterday that since I put the new battery in, only once have I had to try to start the car twice - it starts that much faster now, due, I am sure, to the much faster speed with which it turns over.