I have mistakenly poured about a half quart motor oil (synthetic 5-30) in the filler for coolant. Do I need to drain the coolant or will it be OK. This is a 2007 BMW 650i. Will driving it hurt the car?

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    If you have not started it , the oil floats on the water so you could use a syringe to remove most of it relatively easily.
    – Solar Mike
    Dec 21, 2017 at 8:12

2 Answers 2


Your 650i has a closed cooling system in it, which means you poured the oil directly into the cooling system (as opposed to an open system where there's a surge tank as opposed to a recovery tank). If you haven't started the vehicle, all of the oil should still be in your recovery tank. If you have the main cap off, you should be able to use a syringe (as Solar Mike suggested) or something like a turkey baster to get most of the oil out of your cooling system. You'll most likely not be able to get all of the oil out of the system, but you can get most of it. A tiny amount should not cause you issues. You'll most likely, over time, find a small amount of oil condensating on the bottom side of your coolant cap. Just clean it off and drive as normal.

Driving the vehicle with the oil in the cooling system will reduce the efficiency of the system, which is not a good thing. You don't want to drive it around without removing the oil you put in.


I'd second the syringe approach with an iterative twist. Fill up the cooling access port as high as you can go with distilled water and suction off the oil that should be floating atop. When it gets low add some more and repeat. Maybe even spritz the surface of the water with diluted dishsoap and suction up immediately after. Sop up some of the surfaces that are reachable with a rag, if you use paper towels be careful not to let them rip and leave debris behind. You might even use a large straw or airline tubing from a fishtank if you don't have a turkey baster and just mouth pipette small amounts, being careful not to get it into your mouth.

One tip too, when adding the water use a straw to direct the water directly into the fill port so that the oil isn't disturbed and pushed down. Here's a demonstration of the technique I'm talking about that's often found in chemical labs using a glass stirring rod.

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