Small Engines (Lawn Mowers, etc.): CH18S Oil Pressure, oil pressure sensors, 10w30

Question
Model:CH18S
Spec. No.: 62509
S/N:2413302087
With 10W40 oil at cold start it is 42 psi, during use at full speed @18 psi, idling when hot @8 psi with a bit of valve clatter which fades away when returned to full speed. Using 10W30 drops all the numbers by @3 psi.

All my service manual tells me is to check for 20 psi after cold start.

What is the minimum safe oil pressure for this engine? The oil pressure warning switch operates at 3-5 psi, is anything above that considered OK?

Answer
Hello Rex:

>>As Long as you have at east 20 PSI After Starting the Engine when it has Set Unused for at Least 2 Hours and as Long as it is Enough Oil Pressure to keep the Oil Pressure Sensor Engaged when the Engine is Idling, the Oil Pressure is Good According to the OEM.
>>Idle Oil Pressure Hot will Vary (as you have seen) Depending on the Viscosity of the Oil you use.
>>A Minimum of 3 to 5 PSI is Suggested and Most Oil Pressure Sensors are Designed to Shut Down the Engine if the Pressure is Less, but I like the Best Oil Pressure I can Get so I Use SAE 10W30 (Synthetic Oil) in the Winter and SAE 15W40 (Synthetic Oil) in the Summer.
>>I have Less Valve Chatter at Idle using these Viscosity Oils.
>>If you Hit a Snag or this Does Not Correct the Problem,  I Hope to be Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Be Safe and Happy. Thanks.

Good Luck

Respectfully

John

PS: I am Allowed to Answer 5 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 8pm EST (US). My New Day Starts then. Comments and Ratings are Greatly Appreciated. Thanks.

Respectfully

John