Dataset For Costs Of Vehicle Ownership (maintenance) As The Vehicle Ages?

I’m primarily interested in trucks light duty – medium duty, but I’m struggling to find much data on this specific topic in general other than a few write ups saying that there is a correlation, but lacking any reference actual data.

I’m interested as I have a client that delayed replacing a large swath of their fleet in 2021-2022 and seen a massive uptick in maintenance costs in 2022. I’d like to provide some actual insight into that with data and their historical data is lacking.