In the processes of replacing oil cooler gasket and noticed lots of sludge build up is this normal ? the picture is after I removed all sludge

 

What was the drain and refill interval used on the car?
Many, many posts about the absurd drain intervals from Jaguar. I use a 6K-8K mile range for my oil changes.
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It does look like an old oil issue. Was the filter correct or changed with the oil? Also, was the JLR spec oil used? The spec oil is designed to prevent the coking and this looks like it's been pretty well cooked over a long time. I too change oil and filter every 6K - 7K miles and everything stays pristine.