Drive the IS for business and the Murano for pleasure.
For example, if you need a few yards of manure for the lawn, the IS is perfect for transporting that. (Sorry, couldn't help it...)
But seriously, if it's a company vehicle, drive it only for business and make sure they can not tag it on your income as a benefit that would be taxed.
If it's a friends, ask them what they want you to do with it...
Other ideas that come to mind is learning how to jump a vehicle, plowing snow and demo derbys.
Yeah, I know, a lot of help I am. I guess the problem is, there's no context on the question, as to who is supplying it and why.