Low oil pressure when stopped.

[mjelliott]

My 1994 Toyotr 4runner has low oit pressure when I am stopped but it goes back up to normal when I am moving. The oil level is fine when I check it. Does anybody have any ideas what the problem could be? Thanks

[MagicRat]

Classic sign of a worn oil pump due to many miles. The oil pump mechanism has excessive clearance and results in internal oil leakage.

Less often, this is an indicator of an internal oil leak elsewhere in the oiling system.

You do not state the mileage or if the engine has ever been rebuilt. Chances are, you have high miles.

This problem can be lessened by using thicker engine oil.
Many engines recommend 5W-30, which, in this case is a bit too thin.
(Note, the lower the number, the less viscous the oil and more likely to leak internally.)

Try 10W-30 in winter and 10W-40 in summer. Your oil pressure should improve. (Since you live in southern CA, try 10W-40 all the time.)

In extreme cases, a couple of quarts of 20W-50 first at an oil change, and top off with 10W40 may help. Some people do not like the idea of mixing oil weights, but I have had great success in doing so to 'fine tune' viscosity to compensate for low pressure in worn engines.

Note, you do not want the oil to be too thick, or excessive oil starvation on cold start up may result.

Note this is not a repair, simply a band aid solution. For a proper repair, replace the oil pump (engine removal may be required) or rebuild the entire engine.