When i come to idle at a light, my oil pressure light briefly comes on this has been happening for about 2 weeks. I check the oil and it was down a litre. Last oil change was about 4 months ago, I think i put another litre in about 2 months ago. Car runs great minus the light coming on but only when my RPM drop below 500, Does any have an idea as to the issue and what my normal RPM's should be when idling at a stop light, and also what the RPMs should be when in park?

Thanks so much in advance

 

it minimum rpm your oil pump is at it's lowest output being a liter low doesn't help either
You don't state miles Guessing 100k Plus
You might need a good oil flush

 

the car has about 240,000 k.

so when at idle in gear, should if drop below 400/500 rpm at a light? it almost sounds like its going to stall but never does.

 

the 'load" of the tranny in gear lowers the RPM's

the rpm's in gear sounds a bit low I'm around 800rpm