Regarding oil consumption, synthetic oil is far superior for lubrication than petroleum based oil BUT it has a smaller molecule, one reason why it is superior, and is therefore more easily consumed by the engine.
These Isuzu engines consume more oil because of their PCV system. Misted oil from the crankcase is routed back into the intake and is burned by the engine. If you install an oil trap or "oil catch" to condense the oil so it doesn't pass as a mist into the intake you can put the condensed oil back into your engine instead of losing it. Ebay sells them for 15-30 dollars. They also have an indicator on them to show how much they have collected.
its faulty
on the engine
The oil sending unit in a 1992 Isuzu Trooper is located within the car's engine. The oil sending unit is responsible for determining the oil pressure.
4.2 QTS
At the bottom of the engine oil pan.
low or no oil pressure
with an axe
6.5 quarts
5W-30, preferably synthetic.
Same location where you pour the motor oil
6.5 quarts
No, that's an indication of a problem.