It’s important to use 10 liters of coolant which has Red color. Don’t underestimate the importance of Mazda’s 1.3 engine cooling system. For 2003 RX-8 engine it’s necessary to get normal temperature balance. You may use code of motor 13B-MSP and volume figure of 1.3 or just tell the 2007 year of production to buy liquid. For sufficient use of Mazda RX-8 you need to use suitable antifreeze.
It’s obvious that every 13B-MSP motor needs good service as stated by Mazda in instruction. It will be advantageous to follow Mazda’s rules for 2004 RX-8 service. If you choose other than Red coolant or use less than 10 liters, you can’t expect normal work. Produced in 2003 the 1.3 engine in RX-8 model will serve longer by this.