In standard UK operating temperatures use 10W/30 oil or in colder climates use 5W-30.
As an alternative you can get away with 10W/40 or failing that 15W/40.
It is important to keep a schedule of regular oil changes at 3,000 miles. You need 6 litres of 10W/30 oil for the Bongo according to Mazda.
Place a bowl under the sump plug and undo it using a 19mm socket. Drain the oil into the bowl and then into the empty oil container when you have refilled the Bongo.
Change the copper washer on the sump plug every oil change and the oil filter every other oil change.
The oil cap is under the passenger seat for refilling the oil. Check levels on the dip stick to ensure you have filled it to the correct level.
UK climate: 10W/30
Colder climate: 5W/30
There are many different oil brands out there which make SAE 10W/30 or SAE 5W/30 oil