my own car is 15 years old, it has about 285,000 kms on it and I drive it everyday - I use mobil 1 0W40 (or similar oil from a good source - including some diesel oils) with fleece filters and change it at 24,000 kms
working like a clock - no sludge no issues and I do boot it sometimes.
when I bought it - the previous owner was a bit goofy - he was using paper filters installed by stupid mcidiot mechanic at shady oil change place I think because the filter was not properly seated onto the holder and oil was infact bypassing the filter completely.
the engine sounds like a classic singer sewing machine and has good solid compression and good oil pressure too.