Thanks for the suggestion. An API is a frequent request, though not quite in this way. We'll give it some thought.
In the meantime, you can get some data programmatically through RSS feeds. Every vehicle has an RSS feed that includes the details from the last 20 fuel-ups. You could use that to scrape and mirror the
running average calculations you see on the dashboard.
Otherwise, yeah scraping the site for personal use like this should be fine.