Trust your eyes on this one, 5 quarts is absurd; maybe with a massive oil cooler and some uniquely designed oil pan reserve/sump... but in my experience there is no way the 3.0 can handle that much oil. Case in point: I had a prolonged oil leak around the oil pan and when the stick indicated a low reading (at/just above the lower line) adding just under a single quart of oil put it over the highest mark.
Just put in 4 next oil change and carry the the extra bottle in the glove box or under the passenger seat as we all know a tightly sealed, and non-leaking Montero is a proverbial 'white whale.'
On a personal note: I've really come to despise the Chrysler-Mitsubishi 'DSM' relationship. Just like the Daimler-Chrysler relationship that an ruined otherwise decent made Mercedes chassis.
The Montero would have probably put the Rover debacle off the streets for good and rendered it a pointless State subsidized vehicle (eg Hummer) for the UK military in the 90's had it come with a reliable and far more economical Toyota 1UZ or a variant of it. (I have driven a Range Rover by the way.)
If Toyota and Subaru can tie up now, why not when Japan was trying everything to maintain their cut of the Worlds Market share in the auto industry whilst laws were far more relaxed than they are now?
I have a '89 Montero with the 3.0L V-6. I read my owner's manual and the factory shop manual which both stated that the motor takes 5.0 quarts, including the oil filter. I was changing the oil for the first time since I have owned it, and only placed 4.5 quarts to test the dip stick level. After starting the motor, I let it run for about 20 seconds to get the oil circulated, then shut it down and let the oil settle for a few minutes. I pulled the dip stick and wiped it knowing it is always a false reading; the second time showed the level at about one half quart over the "Full" mark. I spoke to a Mitsu mechanic who said they have never put 5 quarts in the 3.0's?? He said they use 4.5. Has anyone run across this? Any assistance and insight is appreciated. Thanks.
