Is grayscale tex sampler faster than RGB one?

Hi ue4 people.
My question is - is grayscale texture sampler faster than RGB(A), or not?
And how i can measure texsampling performance?


Faster: No but it use less memory. grayscale is 4-8 byte and RGB is 8-16 byte. I don’t now how or if it is possible to measure texture performance.

Thank you for the answer!
I did some experiments, and there is the conclusion - RGB (no alpha, dxt1) tex sampler is a little bit faster than grayscale sampler. In my particular case; on gtx 960.