I degrease metal parts (which aren't solvent sensitive) in varsol. Degreasing before relubing removes old lube and wear particulate buildup. Plastic and rubber parts can be washed with water and mild detergent.
1.5wt oil is very difficult to find. Basically I gave up on hobby suppliers and source my oil from industrial supply. It costs me a buttonne because I have to buy it in a 400lb drum which is basically a years supply. The lightest silicone oil I've ever come across at a hobby store is 5wt which is still a fair bit more viscous.
Want nearly free GBB gas?