The lad's a sparky and bought an import Hi-Ace 3L TD AWD a couple of years ago, the AWD to go surfing and get in and out of the new building sites. (As a tradey you want your tools close but if you've driven dowhill on a clay site and it starts to rain the 2WD boys are out in a flash moving their vans up to the road for the obvious) Anyway I was checking the Toyota Super Custom sites for info(Jap Owners Manual) and there was some interesting info re oil and oil filters, etc. Anyway the Sakura filter it came with was pooh poohed as not fine enough, along with a few other name barands surprisingly as owners had cut them open to check their construction vis a vis genuine Toyota. The OEM had a dual stage filter as has the Ryco z334 so after a couple of genuine Asia Toyota filters off ebay, Ryco it's been since and clearly the price and weight of the Ryco cf Sakura(and no doubt other cheapies on ebay) tells the story. So !0K intervals with any rated CW15 40 it is.
Bear in mind here many manufacturers are lazy and specify 5K/6months largely for Northern Hemisphere markets with snow and ice and if you're not careful and read your temp/viscosity chart you'll probably run too low viscosity. As well manufacturers are always trying to beat green regs and hence using thinner oils (engine drag) which then requires expensive additives to compensate for loss of base mineral oil lubrication and welcome to synthetics to make those green stars. Re intervals bear in mind my missus Mitsi Colt specifies 15k or 12months while her friend's Mazda 3 specifies 5k or 6 monthly. bWhile the missus drivesaround 15k/yr on 3.5L of oil in her shopping trolley, her girlfriend is miffed because she's luck to do 5k a year and those service reminders seem a bad joke. You're not seriously telling me Mazdas and Mitsis run differently on modern oil technology in Oz surely? Mind you that 1.5L CVT Colt is the most fuel efficient petrol motor for its capacity bar none that I can tell but back to diesels.
Diesel oils are all high detergent to keep the diesel carbon in suspension which is why it's black as soon as you put it in while my LPG Commode' 20W50 is still a nice straw colour at 10k. They both need replacing at the same time however, providing that diesel filter has had a very good secondary microfine filtration in it. Black diesel oil is fine as long as those particles are microfine and the oil hasn't run 10k in our mild climate and all those fancy low viscosity synthetics are a waste of dough unless absolutely specified. read your manula and temp/viscosity range and don't be suckered. You don't really think truckies change their oil every 10k do you? They are very particular about their pre-filters and filters though.