Vaseline is like the Singer Motor Lube grease. It melts at 115º and will fling off as it liquifies under the heat and pressure of use. It's good for the Singer motors and others like my old White DRESSMASTER that specifies petroleum jelly in the motor's grease pots, but I wouldn't use it for gears in any machine used to any degree.
Tri-Flow grease is readily available at Sew-Classic and is far more suitable for gears. The white Singer gear grease is also available on line and at the LSMG places.
Joe