Www.dartheads.com for a telephone number they may be able to help you? I bet they liked saying it's a dual quad set up. Or simply liked the way it looked. As for oil I wouldn't run anything with less viscosity then a 30. Not knowing clearances and just guessing I'd run 10W40. With that said I'd run something with a formula that will protect during storage as well as run time. Not all oil will do that.
Where are the pictures?