Back in the 50's, we were distributors for Conoco and we got a new Chek Chart Lubrication manuals every year. I still remember the recommendation was lubricate passenger car springs to maintain a smooth, but to leave commercial truck springs dry because the springs required the the friction. Until we phased out springs in favor of air ride over 30 years, we never oiled springs and service manuals warned against it. In those days trucks leaked a lot of oil, and oily springs broke. It was particularly dangerous on the steering axle because the wrap leaf didn't always hold it. Trailer suspensions have torque rods to keep the axle in place.
I still have 9 dry vans on spring ride and steering axles are still spring ride. DOT regulations tolerate zero oil leaks. I don't remember when we last broke a spring.
