Hi Dannt D,
It is important that you drain the Mobil One right away! Do not use synt. oil for the first 500 miles. I don't use synt oil at all in a Whizzer because it only cost more is thinner, and didn't make any difference on the Dyno runs, and if it helped the gas mileage, I can't find the difference. Because the new Whizzer is a basic copy of the vintage motor using the "splash" oil system, synt. oil "foams" or collects "air bubbles" when beat with the rod "dasher". I was told syth. oil doesn't do what I just described, but my tests show when you drain the synt. from a hot motor it has a foamy texture, and about 1/2 hour later the drained oil looks normal [just dirty], whereas when you drain 40 weight from a hot motor it just looks a dark color [dirty]. I can tell you for sure your rings will not seat, and the piston will not mate with the cylinder if you use synt. oil.
Use straight 40 weight oil, I use Shell brand in all my motors, and have had great results. I have motors with over 6000 miles on them and when I look inside they look new.
If you are losing oil from the center crankcase gasket, contact your dealer to have the gasket replaced. If you don't have a local dealer, just obtain the needed gaskets from any authorized Whizzer dealer on this site [Bill Green, Dallas Maddox, Mike Simpson, Whizzer OuterBanks], and I will gladly supply the needed information to change the gasket.
Whizzer OuterBanks LTD
A North Carolina Coprporation
Quenton