My oil pressure stays at 40 but once i drive for a while it drops were the red light come on when at a red light

If you have the 6.0 you likely need a new oil pump, common problem around 150,000 miles.

Next thing I would check is the oil pressure switch. I have put two of these in my wife's Park Ave. They are 40 bux for the lifetime warrenty one.

ur oil sending sensor is bad it reeds the oil pressure

The Trailblazer doesn't have an actual oil pressure sensor, it's only a switch that closes at about 12 to 17 PSI and the computer makes up a number to drive the gauge. If you know you have a full level of oil, there is no reason you can't drive to have a mechanic check things out.

You mean the light shuts out the truck dosn;t stall right Yes then i would try replaceing the sending unit likely is the cause of the problem

when the thermostat in a beetle goes, it stays in the open position, so it could be you blue light is indicating a "cold system",change the thermostat.
the oil light will come on if low on oil or you have a low pressure,try using 10/40 semi synthetic oil.and mloyslip.if no improvement you will need to renew the oil pump.

Measure your oil at normal operating temp, without the engine running of course. This will give you a more accurate reading once the oil has circulated in the system.

The system works like this:

• With the ignition on, the oil pressure indicator light on the dash should come on and flash. Once the engine is started, the light should go out and stay out as long as the engine is running.
• If the oil pressure drops below approximately 0.3 bar or 5 psi when the engine is running below 2000 rpm, the light will flash.
• If the oil pressure drops below approximately 1.8 bar or 27 psi when the engine is running above 2000 rpm for more than 3 seconds, the indicator light will flash and the buzzer will sound.

If either this two warnings occur:

• The engine should be switched off immediately and the oil level should be checked.
  

Increase the viscocity of your oil. If you're using 10W30, go to 10W40. If you're using 10W40 switch to 20W50. Don't use single weight oil.

When the gauge is at 0, is there any noise from the engine (tick, knock etc?) I would have someone put a mechanical gauge on there and read true pressure.Your driving pressure seems OK but if the low number is "real" something is wrong!

This sounds normal to me! The engine will read that rpm when accerlerating lightly. It is the stall of the torque convertor. The oil pressure will always be higher when the rpm's are higher, or when the oil is thicker - cold.

Virbration? That is a different story. Oil won't cause that.