My 2007 Buick 3.9 liter oil light comes on and off. ..stays on for a while then goes back out. Checked the oil level all good. I did recently change the oil to GTX 5w30 extended milage oil. Any idea

Oil pressure sensor, or most likely, oil level sensor, either sensors, wires, or connections.

If you checked the oil level & it's good, then you're okay. But, keep an eye on it... As long as the situation with the light stays the same, ok. If it starts coming on more often/different times, then you'll have to find-out of it's just the oil pressure sending unit ( cheap ) or if the oil pump might be dying.

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The quoted capacity is just under 4 litres including a filter change.

I put 3.5 litres in, start the engine check the oil light goes out after a few seconds, check for leaks from the filter, then switch off engine.

Wait at least 3 minutes, check oil level on dipstick and top up to maximum.

sounds lie the 'alarm' wasn't reset at last oil change.

You have to reset the check engine oil level light. The light is just a 3 month reminder that lets you know when to change your oil. You have to hold the reset button on your dash for more then 5 to 10 sec. The procedure is in the owners manual that came with the car.

That is the oil pressure gauge not the oil level gauge. Sometimes they can act that way when the oil is thin. When is the last time the oil was changed? Try using a heavier weight oil. When engines wear they require thicker oil. What size engine does you voyager have?

not good, but do not panic until you check actual engine oil pressure

that being said...take the concern seriously because the light turns on when oil pressure is less than 10psi

have you changed your oil recently?
did you use the correct type 5w20

have you checked actual oil level?
I have seen a lot of town cars that burn oil and you may actually just be low

Check oil level first
Check oil pressure second

if both check out then you have an oil pump problem or a more serious engine concern

keep me posted!

some cars with oil level warning light on, it doesn't mean that its only reading the engine oil level is low, sometime the transmission fuid too. Did you check your transmission fluid if it is ok or not? try to check and let us know, ok.

This can be a few different things. I'll give you a couple. First, do you have an oil pressure gauge? If you do, watch it very closely. Specifically while accelerating, braking, and making turns... so, pretty much, all the time except when cruising. If you don't have one, you'll just have to watch the light. More than likely you are losing oil pressure and it has nothing to do with oil level. If it comes on more when the car is idling, but tends to go off when it's revved up, the oil pump may be going out or may be leaking. It could be that it's pickup line is getting clogged, but don't count on it. It could also be a clogged oil filter, but again, not likely. Change your oil AND filter first and foremost, even if you've done it recently. Then watch the light while the car is idling and while revving it SLIGHTLY. BE CAREFUL!!! If you're temperature gauge starts going up or your check engine light comes on, shut it OFF. Lack of oil pressure leads to blown engines. You don't want to spend 3-5K on a new one. Get the thing checked out. One more thing. When you get your oil changed, ask the mechanic to reset your car's oil change computer. Many newer cars will show an oil light when it's time to change the oil. If it's not reset, it won't know it was changed and will stay on. I hope this is your problem. Good luck with everything.

It could simply be maybe the person changing your oil never reset the light? or you have a oil pressure sensor leaking or not working.
most of the time its someone never reset the oil change light. even before it goes on it goes by mileage, so maybe it didnt go off yet cause you cnahged it a tad early.so noone even tried to reset it.

I guess you could have an oil pressure problem, but thats going the extreme route.. but if nothing else shows that could be a problem.