We do manual transmission oils every 20 000km, autos every 40 000. The manual trans only holds 2.3 litres, and auto holds about 8 - 12 litres. Fair to say stretching the change interval is a pretty big ask for any oil.

Bear in mind that we have extreme conditions ( below zero in winter, 45 degrees plus in summer) and most LRs in town get used at least on dirt, if not in proper off road conditions.