Prime95 will definitely get a CPU toasty, but you would need to ensure it's running with a mix of large and small FFT and for a while (e.g. hours/days). Small FFT maximizes CPU heat, but isn't the best for finding instabilities working with RAM. Large FFT helps there. In general, I find the overclocking community sometimes works on "vibes" rather than completely proven test methodologies, so take this with a grain of salt. 

 not that you're overclocking, but that group tends to accumulate tribal knowledge of CPU/RAM stability tests. Hardware can be "fun". A ton of variables. Even things like bios versions can cause instabilities.