oil weight for a 1989 4runner v6 4wd

Either 5W30 or 10W30 will be fine.

it all depends on millage, usually if you have over 75k you want to go with 10w30, if you have over 150k you want to move up to 10w40 and if your over 200k you might want to try 20w50 because the more wear on the engine the quicker it will burn through oils like 5w20 and 5w30 which are usually only used on cars up to the 50k mark

is it ok if i put 15w40 oil in my 89 v6 automatic 4runner

my 4Runner has 281k miles and i still use 5w30 and only have to add 1 quart to 2500 miles. going thicker is not a good idea. First, thicker oil is harder to pump, I have seen the oil pump shafts break off, then you blow the engine, second, since it flows much slower, it is harder to get to all parts of the engine causing more wear, and 3rd, slower oil will make the car harder to start in colder weather.