Happen to have a tube of Super Lube grease from another project and was wondering if anyone uses it on their P series guns ?

I do. It works fine.

I love Super Lube, really a fantastic product, but if we're talking about slide rails, it seems a bit too thick for that purpose. Perhaps a coat of Super Lube with a lower viscosity oil over it, or using it in environments with excessive high temperature.

Other parts of the pistol, lockwork and other parts, I think Super Lube would be fine.

One thing is for sure- anywhere you apply Super Lube, it's going to stay for a long time.

I’ve not used the grease but the normal super lube lubricant has worked awesome for me over the years.