Only to add that the gap between max and min on the dipsticks of my cars is two litres.
Excess oil is a problem in general terms, but 4mm shouldn't do damage.
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NB On smaller cars the gap between max and min is usually about 1 pint or 0.5 litres.
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NB On smaller cars the gap between max and min is usually about 1 pint or 0.5 litres.
Not always the case. With Vauxhall it's generally 1 litre between min & max, regardless of the engine size.
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Whatever amount of oil is needed to lift the level on the dipstick from Min to Max - it will be detailed in the handbook! Don't get it wrong - overfilling is a bad thing, or can be, especially in a diesel.
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80's & early 90's 1400cc Cav / Astra is .75 litre between min / max.
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Peugeot/Citroen 1.9 TD engine- 1.5 litres between max and min on dipstick. I always fill my 306 up to just below the maximum (about 4.25 litres). A mechanic stressed to me never to go above the maximum on these engines as the turbo will suck the oil into the engine, causing it to run past its governed limit and self-destruct.
Martin
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The oil may get into the engine and burn in an uncontrolled manner but SFAIK it will not be thru the turbo. The turbo is driven by exhaust gases and takes in fresh air which goes to the engine.
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In this instance, the oil is sucked into the air side of the turbocharger via the engine crankcase breather pipe. The engine can then "run away" by running on the oil mixed with the air charge.
Generally, I don't think most engines will be harmed by a moderate overfill - but note that most engines have tapered sumps, so volumetric ratios in relation to oil levels on the dipstick are not usually valid. Remember that an engine designer has to make the engine safe to start and run when the vehicle is parked on an unfavourable incline of the order of 25%. If you avoid this marginal condition with a slightly overfull engine, damage is unlikely.
The only engines with serious problems due to overfill which I have encountered are PSA diesels. My suspicions are that they raised the oil levels to permit longer service intervals - in any event I have seen leaking crankshaft seals (and consequently oiled timing belts) on these engines with the oil at max. Running the oil at 3/4 full (on the dipstick) resulted in a completely dry engine.
659.
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659FBE - thank you for that clear explanation - I had forgotten about the crankcase breather!
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Gross overfilling can result in total engine failure. Reason: crankshaft is immersed in oil and creates bubbles which get sucked into oil pump leading to oil starvation.
The late unlamented British Leyland managed to mismark the dipsticks of early 1800cc B series engines so careful users who checked oil overfilled them .. and on long runs this resulted in engine failure...
madf
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Gross overfilling can result in total engine failure. Reason: crankshaft is immersed in oil and creates bubbles which get sucked into oil pump leading to oil starvation.
Thanks for that - I've always wondered why the crank coming into contact with the 'bath' of oil in the sump was so bad. I read it somewhere, but they didn't explain...To me it seemed like it would get extra lubrication!
So if the oil didn't foam, would it be safe?
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Gross overfilling can result in total engine failure. Reason: crankshaft is immersed in oil and creates bubbles which get sucked into oil pump leading to oil starvation.
The thrashing of the crankshaft in the oil also causes excess loads on the bearings. When the manufacturer says maximum they mean maximum.
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L\'escargot.
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The thrashing of the crankshaft in the oil also causes excess loads on the bearings. When the manufacturer says maximum they mean maximum.
Is that literally caused by the CS having to move through something rather than just air?
What normally lubircates the CS bearings?
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The oil pump puts oil under pressure through the galleries in the crankshaft through the oil way in the shells.
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The oil pump puts oil under pressure through the galleries in the crankshaft through the oil way in the shells.
Except on engines with splash lubrication. I had an old prewar Ford engine that had speciall scoops on the big ends, to dip into the oil and splash it around inside the crankcase.
I'd also observe that the recommended oil level cannot be all that critical. A car climbing an alpine pass has to have an engine rated for constant running under heavy load at a considerable angle. The downhill bearing might be a lot lower than the uphill.
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