I'm going to be changing the transmission fluid on my G35 but I have a few questions to ask. Im just going to do a simple drain and fill which i believe only gets out about 5-6 liters of fluid. The nissan matic j fluid at the dealer is about $15/L. I know Castrol makes an ATF fluid which meets nissan matic j specs which costs about $6/L. Now here is my question....will it be okay for me to use the Castrol ATF since only half of the fluid is being changed and it will be mixing with the matic j fluid thats left behind?

 

I recommend not taking the step of mixing non-Nissan brand ATF fluid (even if it says it meets J-matic spec) with existing J-matic fluid. That could cause potential harm to the transmission, and Infiniti may not fix it under warranty. Infiniti says in the owner's manual that ONLY genuine Nissan J-matic fluid should be used when changing the ATF, nothing else.

When I did a drain and refill of the ATF a while back, I purchased 4 quarts of Nissan J-matic from a local Nissan dealer for $43. This was enough to do the job, even though it will only get rid of 30-40% of the old fluid (rest of the fluid is in the torque converter which requires a fluid flushing system to be hooked up).