OP, I don't break it down by mile but I do look at my previous purchases and determine what it cost me per year of ownership. This is calculated by what I paid less what I sold it for divided by the years I owned it.
Harley - $280 per year
Coleman pop-up - $167 per year
Last pickup truck - $1,020 per year
BigFoot trailer - $0 per year
Jet Ski - $150 per year estimated because I haven't sold it yet.
Current trailer - Still have it
Current truck - Still have it but $175 per year based on KBB
This helps me affirm that I usually make pretty good purchase decisions.