ok so if I change the oil every 10k how will the car know? will I have to reset the ecu each time? can I use a fully synthetic oil in this engine? and if so do I need any particular viscosity? eg can I use say 5w-40, as this is fairly common and easy to get hold of.
Use fully synthetic, top stuff! I had a V reg 110 Toledo new in 2000, company car & screwed the living shite out of it! 'Chipped' it from 2000 miles & boy did that poor car have some death! However due to my extreme driving I changed the oil myself in between scheduled services (ie every 5k) always with fully synthetic and also had the dealer use fully synthetic. That car has now done well over 200k miles, as far as I know is still 'chipped' & still going strong with very little oil consumption.
Following the Toledo I had a Mazda 6 TD, same thing, fully synthetic every service, not so much of a hammering (getting older!), but after 90k was still good - Mazda specify semi synthetic for the 6 TD but they have had some oil pump failures & severe sludging on high mileage cars - no probs with mine on fully synthetic!
My feeling is, even if you are a very high mileage driver & therefore needing services often, for the extra tenner go fully synthetic. Semi synthetic is exactly that to me - half a job!!