2004 vs 2005
 

The 2004 RX-8 has many problems according to consumer reports. It received a poor rating in Fuel and Ignition, which include:
Fuel: Fuel injection, computer and sensors, fuel pump, tank, emissions controls, "check engine" light.
Ignition: Spark plugs, coil, distributor, electronic ignition, sensors and modules, timing.
The 2005 received excellent in all categories except paint/trim, where it received a very good.
So if you're having problems with your RX-8, maybe you don't have to ditch the RX-8 all together, just the year.

Actually, that is exactly what I did. I had an early 04 and went through all the reflashes and weak air conditioning issues, finally sold it even though despite all the issues I still loved driving it, just couldn't deal with the miserable air conditioning and the dealer couldn't get it to be any better. I now have on 05 and it has no problems at all and gets better gas mileage.

Um...the 05 has better A/C and gas mileage than an 04? News to me.

I don't know if they do in general, I just know that my 05 has stronger ac and better economy than my 04. They must have done something because there is also a huge difference in ratings in Consumer Reports between the 04 and 05. I used to darn near die in the 04 on a hot day, the 05 doesn't spit ice cubes but it much better.

I have a 5/2003 build 2004 RX-8. Yes, I have experienced a few problems that have been fixed on the 2005s, but they have all been covered warrant TSB repairs.

My impression is that gas mileage may vary from vehicle to vehicle and it is unclear whether the 2005s have better mileage. Some of the engine PCM updates have improved mileage slightly however, Mazda has not changed the The EPA number on the sticker.

No, I would probably not buy a 2004 that was out of warranty, just in case the previous owner had not been careful to get all the problems fixed.

I purchased an '04 a few months ago. So far I've only had to have a new selenoid, other than that I've had no problems, yet.