I have tried Nova Montgomery's lubricant.
I had previously lubricated the gears/pots that lubricate the bearings on the motor on my Singer 15-91 with Tri-flow lubricant and the machine was so bogged down that the motor wouldn't run faster than slow. I painstakingly wiped off as much Tri-flow lubricant as possible and since I had just gotten some of Nova's lubricant I thought I would try it. The slow motor problem was solved! I couldn't believe the difference in how the motor performed just based on a different lubricant.
I went back to the Sew-Classic website to read what Jenny said about Tri-flow lubricant and I found out that she doesn't recommend Tri-flow lubricant for grease tubes or pots that lubricate motor bearings via a wick. That was exactly my situation with the 15-91.
I haven't done a comparison with Nova's lubricant vs Singer sewing machine lubricant.
I have no affiliation with Nova or her products but so far I'm pleased with her lubricant.