Dealers are greedy, don't use them for any paid service after the warranty expires. They usually charge more just for 'Diagnostics' than it costs to repair any issue with independents or DIY. The last time I used a dealer I was charged $800 to do a HV battery test because I was low on range and...
I also changed both my i3 REX's cars a few weeks ago. Both cars old oil looked brand new despite being 2 years old. I sent one for Blackstone analysis and they said the oil was completely fine to use for another 8k miles. I doubt the old oil had even 10 hours of run time.