Hi,
Two things, First don't use the Lucas in anything, I'll attach a link for this.
http://www.bobistheoilguy.com/images/lucas/lucas.htm
http://www.bobistheoilguy.com/
Second The 10w means that the oil will flow at freezing(I forget the actual temperature)
& there is no loss of it's lubrication ability, your engine builder is just trying to keep you from having a cam failure, & for him, this may be his fail safe, if you don't follow his directions you'll void the warranty, it's a judgment call on your part, your coming up on the 500 mile thing, the weather is warm so there is no start up problems with the oil being to thick, but come end of fall you'll want to use a multi viscosity oil, so I think it would be okay to go to a multi viscosity on you next oil change if you choose to, just use oil that will help keep the cam alive, like brad penn.
Rich