Synthetic is what Isuzu recommends, its written very clearly under the
hood. Despite this, every service for the past 4 years has put in el
cheapo oil... (10-W40,  20-W50). Its the reason I always try another
service station place. One thing I did notice is that the Trooper uses
no extra oil when the normal stuff is used...  Mine is a 7/99 with a 3.0
common rail diesel engine. Apparently synthetics are even more important
in these engines but as I say the austrian mechanics dont give a damn.
Obviously if you change your oil yourself you get what you want. Mine
just has one service / year, about 73000km on the clock now.
Love this 4x4, if Isuzu doesn't bring out any more such models its my
last vehicle. Its been rebadged by Opel but Opel itself never made such
quality. End of the week we're taking it on a holiday trip to the Greek
island of Lefkas via the ferry from Venice.  Curious how the Trooper
will take to coastal life and the greek roads which I hear are '4x4
optimized'  :-/

madiba