Oil pressure pump

Here's a link,it's a camry,but they use the same engine as lexus 3.0.

May be low oil, low oil pressure (faulty oil pump) or a bad pressure switch. When your at highway speeds the pump, pumps faster & brings the oil to the right PSI. Try a thicker oil than called for, get the oil pressure checked,oil leaks? & get the switch ckd out.

if you ran out of oil and you now can hear knocking sound comming from the engine then it time to get it checked by a mechanic

How do you describe "loses power" ?
Does the engine stop, or what ?
If oil pressure drops below 5psi and the light comes on, you could lose power to the fuel pump.

It looks like that the cause of your leaking pan gasket is excessive blow-by gases pressure due to worn out piston rings. The low oil level is a telltale sign the you are consuming (burning) oil because of this problem.
I recommend that you have a ring and if possible also bearing job to your engine. Merely replacing the torn out gasket will just temporary solve your leak problem. Since you will still burn oil, your emission problem will not be solved.

IF TRANSMISSION LEAKING WHILE RUNNING LEAKING AT TORQUE CONVERTER SHAFT SEAL OR TRANSMISSION COOLER LINES GOING INTO RADIATOR LEAKING.YOU WILL LOSE MORE FLUID AT COOLER LINE BECAUSE TRANSMISSION UNDER PRESSURE THE OIL PUMP PUMPING IT THROUGH THE RADIATOR YOU WILL LOSE ALL YOUR FLUID QUICKLY IF LEAK COMING FROM COOLER LINES GOING INTO RADIATOR.DONT DRIVE VAN UNTIL FIX BECAUSE FLUID LOST WILL BE TRANSMISSION LOST.

I recommend taking the vehicle to a mechanic to check the oil system. You should not have to put oil into your car that frequently -- it probably has a leak in the system, and fixing that should help you out. While they are checking for leaks, you should also have them take a look at your oil pump -- if your pressure is always low, you probably have a weak pump that needs replacement (or the pump itself might be where you are losing the oil -- which would mean a new pump would keep you from losing oil as well as help stop the ticking and the pressure problem. You can probably go to a junk yard and get a used oil pump pretty cheap -- if you are confident in your skills, you should be able to replace it (probably for less money than having a mechanic look at it) so this might be a good first step. If that does not solve the issue, take it in for a check-up. If your oil system fails while you are on the road, you can ruin your engine and end up costing yourself a lot of money in the long run.

Not unless you were leaking huge amounts of oil. Low oil pressure is from worn clearances on the engine bearings or a weak or restricted oil pump.

Well furst of all fix the leak before you have a fire.

I do not know your model of vehicle. But low oil pressure is usually an oil pump problem. If it is not sorted out soon, you will need another engine.