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Cardoctor74, ASE Certified Technician
Category: Mazda
Satisfied Customers: 25954
Experience:  ASE master technician
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Mazda: main oil..castrol edge c1 5w-30..synthetic oil

Customer Question

I took my RX8 to a Mazda main dealer for a service. On returning home I noticed on the invoice that the cars oil had been replaced with Castrol Edge C1 5W-30. To my knowledge, this is a fully synthetic oil and therefore not compatible with the RX8's engine. I have had a discussion with the service manager who tells me that Castrol had confirmed to him it was.
I'm still not convinced or happy that the Mazda Dexelia oil wasn't used. Can you clear this issue up for me please?

Submitted: 5 years ago.
Category: Mazda
Expert:  Cardoctor74 replied 5 years ago.
Never use synthetic oil for an RX-8. The synthetic oil will produce a film on the inside of the engine because it does not burn with the gas. It will also void the warranty if you have problems and they find out about the synthetic oil use.
It requires 5w-20 NON SYNETHIC because the oil is injeted and cooled through a OIL/AIR COOLER. SYNETHIC OIL WILL NOT BURN, not allowing the engine seals to be lubed, thus your RX-8 will become an oil leaking RX-7.Please DO NOT use synethic oil.Hoped this helped. Positive feedback and bonuses greatly appreciated.
Cardoctor74 and 2 other Mazda Specialists are ready to help you
Customer: replied 5 years ago.
Thanks for your information. The dealer in question is changing my oil and filter tomorrow thanks to your response.
Expert:  Cardoctor74 replied 5 years ago.
Anytime glad to help.