I find you need to be at 50 degrees for it to start noticing the difference that needs to be in your mind when testing it.
Yes I know. All my vans have gas heaters now. We run at 60 degrees
Lee , what gas heaters do you use ?
And i think that the above 50 c bit is a bit wrong , any increase is going to clean dare i say "better" than ambient temp .
If you go out with stupid hot water on a proper cold day you are looking at thermal shock territory .
I use the L5 and it gives me about 35/40 at the brush head , that it more than ample for my needs , i see an improvement on using cold and its more of a comfort and hose managability issue for me anyway .