I have a 5500 and have been very please with it - so far (only 33hrs).
Please let us know the NAPA filter number for the oil filter you found that will replace the Mahindra OEM oil filter, and any others you may have discovered. I think they'll be the same for 4500, 5500, 6000.
My nearest dealer is 70 mi. away & I am not sure they stock a lot of Mahinda stuff. The dealer I bought from is 125 mi. away but I feel sure they stock the common Mahindra filters, there is a NAPA store right here in town.
When I bought my Mahindra I asked about the cost of a complete filter change out, all filters routinely changed. The dealer ran up a list and it was a little over $100.00 - not to bad but a long drive.
It would be interesting and very beneficial to me, and others if anyone that has found other filter cross overs for OEM filters that might be available locally would post their findings.
Thanks
4570 Forever