Chrysler Repair: 05 PT Cruiser: oil light, turbo whirring, oil light, oil pressure

Question
I have a 2005 PT Cruiser touring edition.  About a year ago I had to replace the turbo.  It's been running great since then but on the 18th I had the oil changed and since then when it's first started the oil light is on and stays on for quite a while before turning off.  If I accellerate the turbo (or what I believe to be the turbo) makes a whirring noise but then the light goes off and the car runs fine.  Any idea what the problem could be?  I took it to the shop but of course the car wasn't doing it then and they couldn't find anything wrong with it.

Answer
Hi Chrystal,
It may be that the whirring sound is the nurmal sound of the turbo being called into duty when you accelerate.
The oil pressure light is coming 'on' when you are at idle (but I assume goes off when you go above about 1200 rpm, correct?) and that could be due to the oil pressure sensor being a bit pessimistic about what the pressure actually is or it may well be that the engine may be running at a slightly below normal oil pressure due to natural wear over the miles that it has run.
I would start by looking at the oil change receipt that you got when you last changed the oil.
If it shows they used 5W-20 that would be what is recommended when the vehicle is new. However as wear on internal parts begins to occur inside the engine the pressure will normally drop with time and at low rpm it is common to have the oil light 'on', but it should go 'off' as you move up from idle rpm.
One easy way to get the light to stay off at idle is to change the 'weight' (viscosity) of the oil one step upward, i.e., use 10W-30 oil at the next oil change (or even do it now if you don't mind paying again). Another approach, if you are having to add oil between changes is to add 10W-30 oil instead of 5W-20. That causes the pressure at a given rpm to be higher and most likely the light will then stay 'off' even at idle and the engine may run more quietly.
If the light ever comes on when you are driving at over 1200 rpm then you would want to stop and make sure you aren't low on oil, and if not then have a shop measure the actual oil pressure with a gauge. It may be the sensor that turns on the light is not accurate, for example.
So increase the oil 'weight' is the least expensive thing to do now.
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Thanks,
Roland