If you could get over 20" hg vacuum, it would help. If you are changing cold oil, forget it. The dip stick probes are such a small diameter, you need to have the oil HOT in order for them to perform. Is the tank ASME rated? If so, it will have a large metal tag welded on the tank stating what pressure it is rated for. If it is not an ASME rated tank, be aware that you could collapse the tank with too much vacuum. At this point, I don't see what you have to lose by using your refrigerator pump to create a better vacuum.
I have always wondered how much vacuum is created in a John Dow Industries evacuator. 15"hg is not adequate.
