When looking at the Grim Dawn folder where save games are kept and finding the options file the setting "threads" was set to 1. I set it to 4 because the GPU is quad core. Now the game runs faster with about a 10 fps increase. Loading times are also cut by half. This may be old news but was so pleased with how much better the game is running I thought it would be of interest to some

It's in the end of the file options.txt in C:\Users\[user]\Documents\My Games\Grim Dawn\Settings
forceSingleProcessorMode = false
maxResourceThreads = 1

I wonder about "= true" and ">= 2" ...

Haven't tried this yet, but looking at that, use both options.
Better still, change the "2" to however many processor cores you have.