Can I run my old, slower RAM with my new, faster RAM?

[Taco Annihilator]

I just installed 32gb (2x16) of DDR4 3200 mhz CL16 G.Skill RAM, but I still have my older 16gb (2x8) DDR4 2133 mhz CL15 G.Skill RAM. Would I get any reasonable benefit from running all 48gb of RAM or would I be better off keeping the other two as spares? Note: I already tried overclocking my old RAM to the same speed and timings as my new RAM, and they just can't be overclocked. Thaiphoon burner says they're bottom-bin and I've had the old kit for 5 years.

 

Timings:

32gb kit: 3200 mhz CL16 (16-18-18-38) at 1.35V

16gb kit: 2133 mhz CL15 (15-15-15-35) at 1.20V

 

Specs in case it matters:

Ryzen 5 3600

RTX 2060

ASUS X470 Prime mobo

32gb DDR4 3200 RAM

[Oshino Shinobu]

You can, but the faster sticks will adjust to match the slower RAM, so the speed benefit will be gone. Only benefit would be if you actually use more than 32GB. If you don't, you'll see no benefit from running the slower stuff as well. 

[Guest]

Yea leave em' out is best imo. Hang onto them just in case.

[Dedayog]

You can, but I wouldn't.  It will only slow down your new RAM and do you ever go over 32GB of usage?

[Taco Annihilator]

1 minute ago, Dedayog said:

You can, but I wouldn't.  It will only slow down your new RAM and do you ever go over 32GB of usage?

No, in fact I'm using just over 16gb of RAM as we speak. I just wanted to get the most out of my PC.