I also used the Jim Carter's Gray Engine Paint and I love it. I have seen engines painted with the Filling Station paint and they look very good too. Here is a picture of
my engine painted with the Jim Carter's paint.
I believe this darker gray is correct. And in the right light it has a bluish tint to it but its not blue/gray by any stretch - its dark GRAY!
Interesting, I have had a lot of comments on the color from the younger folks who have never seen an engine painted in this color before. With engines now being painted black, in a way we are sort of returning full circle.