I changed gear oil and after some research decided to go with AMS synthetic severe gear 75-90. I had been using the Yamaha synthetic gear oil and I have a little of the Yamaha oil left, but not enough to fill the reservoir. Is it OK to empty the remaining Yamaha gear oil into the AMS oil container for my next gear oil change since they are both synthetic and similar in weight? I hate to waste the expensive Yamaha oil.