First of all dear your existing RAM has an CAS latency of 10 which comes under loose timing. Now you've purchased another RAM with CAS latency of 9. Speed is not that much an issue. Both RAMs are not compatible.
Using RAM with 1.65 SPD is not safe. This is precautionary note.
If you are fighting for every single FPS then dear remember always go for lower timings of RAM i.e lower CAS Latency like CAS of 9 in your Crucial RAM.
Here is my recommendation, though you can manually play with timings and multipliers to get these RAMs work together, I would still recommend you not to use second RAM.