My car went in for service earlier this week and ended up getting a new (reman'd) drive unit and a loaner battery while my battery goes back to Freemont. What's the general concensus when replacing parts like this? Do I keep my lifetime numbers going or reset? I'm leaning towards letting it roll, especially since I've only put on 3,500 miles.
I don't know if there is a consensus. But here's what I did (I had a drive unit replaced about 9 months into ownership...):
In this thread, I report my total lifetime number since purchase (I post an update every couple months). But I also track everything in a spreadsheet, and I have one table with the calculated Wh/mi on the first drive unit, with another calc since (and I posted a reference to it in this thread a while back). Interestingly, I immediately saw better Wh/mi with the 2nd drive unit -- and my Wh/mi is ~10% lower since (replacement was almost 18 months ago). I have another table where I track the Wh/mi on each set of tires (seeing similar #'s with my 2nd set, which are the OEM Goodyear 19") -- I set this one up since I'd be curious to see if the Primacy or another LRR tire really does have the ~3% better range that Tesla says, but I haven't had a set of LRRs yet....
Because I track my energy use readings in that spreadsheet, I use Trip A for the current month, and Trip B for the current year (based on purchase date), and then the spreadsheet calc the lifetime #. I just use calendar month, even though I received my car on June 4, 2013... I also track other things in that spreadsheet -- firmware updates, supercharger use, non-supercharger range/100% charges, etc. Basically I take a picture of the energy use info and enter that info into my spreadsheet once or twice a month.
I've never done this level of tracking for any other car (although I did track MPG on my previous 2 cars using the Gas Cubby app). Like most of us, this is my first EV and I was really curious to learn how it behaved... The tracking probably takes me ~15 minutes a month and has helped better me understand the car...