A 10w30 CI-4 'diesel' oil seems like a good choice, for storage as well as regular use. It's not a common oil as 15w40 is typical for diesels, but Ford has Motorcraft 10w30 CI-4 for $2.60 a quart. Chevy/GM might offer a similar weight and rating for their diesels. A bit pricey for regular use but it seems like a good price for special use.
Another choce would be 'regular' 10w30 oil with Mobil 1 Truck and SUV, which is a CI-4 5W-40 synthetic. I use 2 qts of Mobil 1 T&S with 3 qts of regular Mobil 10w30 in both Taurus sedans, and am looking around for some more 10w30 CI-4 oils. Delvac would be perfect.