Hi. I want to completely flush the transmission on my 2014 Civic. I put in the Castrol fluid that is compatible for both CVT and HCF-2 a couple of weeks ago. The shifting was hard right after I drained the oil and put in the Castrol oil. After letting the engine running for about a minute or so, the shifting was smooth as normal. I want to flush the trans completely and refill it with the OEM HCF-2 oil as recommended by the user manual. How many quarts of oil do I need? Should I flush it or drain it and refill it with the OEM oil?

 

It turns out that the 2014 civic does not have the supply and return lines that run through the radiator. The transmission is circulated by cool antifreeze that is circulated through out the transmission. So a complete flushing process can't be done. I went ahead a did the following steps.
1/ Opened the check valve nut
2/ Opened the trans drain plug and drained out the old trans fluid
3/ Closed the drain plug
4/ Refilled the trans with the same amount of fluid that was drained out
5/ Started the engine
6/ Shifted the gears from PRDLS; waited 3 sec between each gear
7/ Turned off the engine
8/ Drained out the trans fluid one more time to get the old oil out of the torque converter
9/ Closed the drain plug and refilled the trans fluid til the oil flows out from the check value opening
10/ Repeated steps 5 - 7
11/ Closed the check value plug
My car is out of warranty. So I used Castrol Transmax/Uinversal fluid that the bottle says is CVT and HCF-2 compatible, which I got at Walmart for $20 per 4 quartz. I'll see how this oil works. The shifting has been smooth so far. If I feel the trans is not working right, I'll put in the OEM HCF-2 fluid.

 

Correction:
Check valve nut is called "check bolt"