Oil Light Comes On When Car Starts

Hi I have a simple situation with hopefully a simple answer… I have a 2002 BMW 330Ci. When I start the car the oil light comes on for 10 seconds or so then turns off. The manual says it means the oil is getting to be a little low. However when I measure the oil level with the dip stick (properly 5 minutes after car reaches operating temperature and then is turned off) the oil is at the full mark. My mechanic said the dip stick is always accurate and the problem is not urgent. I vaguely remember having to replace the dip stick a couple years back because of inaccurate oil readings if I remember correctly. And sometimes the new dip stick gets so stuck I have to exert some force to dislodge it from the dip stick receiver when reading the oil. I assume the receiver can take such force without becoming compromised.

What’s the prognosis? Does it need to be looked at ASAP? Should I order a new dip stick? Anything else to consider?


Since the car is an obvious relic you can just perform evil experiments on it. Bad advice follows. Try putting an ounce more oil in it and see what happens. It could turn the light off. Here’s hoping you don’t really have a problem. Make sure you are using the right oil. It may take a BMW guy to know if that light could mean something else in addition to what the manual said. Do remember that I wasn’t the best auto shop student in 1972.

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My first reaction is that the bearings have worn to the point where the clearances are so large, the oil pump can’t generate the needed pressure.

It’s also possible that the oil pump is worn out or the pressure sensor is bad. So how much do you want to spend to figure this out?

I like DodgeVan’s approach. If that doesn’t work, try measuring the oil pressure, then changing the sensor. After that is the oil pump and while the oil pan is off, measure the bearing clearances.


I’d attach a mechanical oil pressure gauge and see what’s happening. First guess: a bad pressure sensor.

Any doubt that the dip stick is the correct one? This problem didn’t start with its replacement did it?


In addition to the very valid suggestions regarding the oil pressure sensor and the possibility of worn bearings, I have to wonder whether the problem could be the result of a build-up of oil sludge in the engine’s oil galleries and other small passages.

How many miles are on the odometer?

What type of driving is the car usually subjected to (mostly short-trip/local driving, mostly highway driving/ a mixture of these two patterns)?

Has the OP consistently used the correct grade/type/viscosity oil, as specified by the manufacturer?

Has the oil been changed as often as it should be, meaning that the OP takes the elapsed time factor into consideration, and is not using only odometer mileage when it comes to the timing of oil changes?


When starting an engine, it doesn’t take much oil pressure for the oil indicator light to turn off. It’s often on the order of 5-7 psi. If it takes 10 seconds just to build up 5-7 psi of oil pressure, something is clearly wrong.

As others have noted, verify the oil pressure with a mechanical gauge.

If the mechanical gauge shows oil pressure quickly rising to psi levels much higher than 5-7 psi, then you may have a bad oil pressure switch/sending unit.

If the mechanical gauge aligns with your oil light, (meaning it takes 10 seconds to reach 5-7 psi), then I would drop the oil pan to see if the pickup screen is clogged. If it’s not clogged, then as previously stated, it could be your oil pump or worn bearings.

Did this just start happening suddenly? Or did it start a while ago and slowly get worse?

How many miles on the engine?


In case the OP is not familiar with oil sludge, this is what the inside of a similar BMW engine looks like because it wasn’t maintained properly.



@texases I don’t think the dip stick is the wrong one I think the mechanic bought this one for me. If I did it I would have gotten the right one anyways I wouldn’t have made that mistake. I do remember lining up the old and new dipsticks side by side to make sure they were identical. Everything’s been fine with the oil system light up until about 2 weeks ago and the dip stick’s been used for at least a couple years or so now.

@VDCdriver ~140K on the odometer. The car is subjected to mostly short-trip/local driving and I only drive like 1500 miles a year with the occasional 7 hour round-trip vacation every 2-3 months. I’ve been using 5W-40 synthetic as the manual says (not BMW oil though as it’s supposed to be and also the mechanic has put an additive in during oil changes that’s supposed to slow oil burning on old cars and also clean the camshaft? - I think). I just get the car serviced when the dash indicates it’s due.

@JoeMario This just started 2 weeks ago suddenly. ~140k

I’m no car wiz so I’d have to take the car to the shop to do almost all of the things mentioned in the thread. The question is then should I have it serviced ASAP or not.
Thanks guys!

You need to have them hook up a mechanical pressure gauge ‘at your earliest convenience’.

How often is that?
With that type of driving, I would change the oil every 6 months.


I would agree to check the actual pressure with a mechanical gauge, but the other question I what brand of oil are you using? I had to make a special trip to the dealer for bmw oil on my son’s car. He was told to only use bmw or one other brand that I don’t recall now.

Edit: so it’s the oil level light not the oil pressure light.

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Drain oil and measure volume.

That usually means there’s a problem with the oil pressure switch.


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A red oil lamp is for low oil pressure, a yellow oil warning lamp is for low oil level.

If one of these monitored switches has failed, it is not an emergency.

BMW recommends changing the oil at a minimum of every two years.

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Now maybe, but for this 2002 model car it was probably more like every 6,000 miles or six months, whichever comes first. Details would be in owners manual.

It is possible, with today’s oils, BMW has retroactively changed their oil recommendations for their 2002 engines, but without knowing that for sure I’d stick with the change intervals they recommended when the car was new, but use present day oil, which is probably semi or all synthetic.

But, that recommendation is based on using BMW-approved European-spec oil, and it sounds like the OP isn’t using European-spec oil.
(OP: Please correct me if I am wrong)

The algorithms that activate the oil change indicator on the instrument panel are based on using Euro-spec oil, and because the car doesn’t know if other, “lower-grade”, oil is being used in the engine, the indicator on the instrument panel can’t be relied upon to turn on at the appropriate time for changing non-Euro oil.

This is what the Chevron folks have to say on this issue:

BMW uses a maintenance computer to determine scheduled maintenance based on use, with a maximum of two years as shown in the owner’s manual.

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Nevada brings up a good point, which is: What color is the oil light?

I was assuming it was red. But now I realize it could be yellow.

Hopefully, for your benefit, it’s yellow.
Let us know.

@JoeMario Sorry forgot to mention that detail, it goes yellow. The manual says if it goes yellow then turns off it’s a little low, top off at your convenience. Yellow that stays on means fill asap. Red is stop the car immediately.

Thank you for that update.

Given it’s yellow, and given that it started only two weeks ago, I agree with Tester and Nevada that it’s likely a low oil level switch gone bad. That would be very good news for you.

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