Welcome to the community, Peter! It looks like you're using a 1st generation adapter, which doesn't officially support diesels yet. Until we release firmware 1.0 for owners of the 1st generation adapter, your MPGs and trip cost estimates won't be completely accurate. Here's a link to a related FAQ on diesel support. We don't have an ETA for when the firmware will be released, but once it's available, we'll make an announcement here in the community.