So better gas mileage than 20W-50? Gear oil? What? Also note that a published report showed a 4% variance in energy density for gasoline sold at the same station. So unless you are seeing a pretty significant change I'd be careful trying to attribute it to your oil.
And congrats on the first instance I've seen of Mobel. Usually people just make do with Mobile.
1994 BMW 530i, 215K
1996 Honda Accord, 224K
1999 Toyota Sienna, 365K
2000 Toyota ECHO, 260K