You are looking at about a 5% concentration of antifreeze. If it's glycol based I would drive it to your garage and get it changed. You will probably boil some of the water off, but pure glycol is soluble in oil IIRC.

I have had an oil cooler fail in a car and the coolant and oil mixed, it happened on a 200 mile journey so I don't know how long I was driving with it like that. Didn't do any long term damage ( the car fell to bits, but the engine was still sound!).

I'd drain it fully where it is without starting it again, then bung in some cheap as you can find unused engine oil (any old 10/40 tat will do for this but you could always bung some flushing oil in and kill two birds), run it for 20 mins or so to clear the system out, then drain out (properly via drain plug both times) and put in proper new oil and a new filter.

Note, whilst draining the first contaminated lot, i'd feed a couple of pints of oil into the filler cap in order to run down the same route the coolant will have taken hopefully washing any residue down with it into the drain bowl.

If the rocker cover is easy to remove i might be inclined to whip it off and see if any clumps of the stuff are sitting in there first of all easily removed with a sponge or similar.

If its been run i'd buy a cheap filter to use with the cheap/flushing oil, then put another new one on when finished.

Might seem an overreaction but some autos suffer with seepage as they age in the radiator, and coolant ends up in the auto box, without fail it ruins the box completely, so i wouldn't be risking it in my engine either.

edit, i'm assuming this is neat anti freeze which i view as worse case.

So easy done, if you saw the state of my skip (garage) its a wonder i haven't done this..;)

Edited by gordonbennet on 27/10/2013 at 12:46

Ooops! Do not start or run the engine. The oil needs draining the engine flushing and then fresh oil. The oil filter should be changed at the same time.

Might need recovery to a mechanic unless someone will do it on the drive, not likely in this weather! You could do it yourself if you feel able?

Cygnet

Bad luck - so easy to confuse! Given the smll quantity involved, I'm sure Collos is right, but for peace of mind you could ask the dealer's advice when you book it in.