Risk to cat

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Mon 10 Jun 2002 20:37
Risk to cat - jud
On the engine oil filler cap there is a notice saying "To avoid damage to the catalytic converter do not over fill". I am aware of the back/front crankcase bearing seal scenario but how does the excess oil damage the cat?
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Mon 10 Jun 2002 20:46
Risk to cat - John Davis
Jud, I am no expert and this suggestion is only an opinion but, I do know that engine oil, getting through the exhaust system, does damage catalysts. Might the overfill warning be there to ensure that excess oil is not forced past the rings ? Crankcase compression, and consequent "pumping" of lubricant up the bores, should be minimised by an efficient breather device but, possibly, with excess oil in the sump, there could be a risk of some "blow by" in the cylinder bores.
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Mon 10 Jun 2002 21:41
Risk to cat - Cyd
quite correct John.
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Mon 10 Jun 2002 21:57
Risk to cat - jud
So if the engine has bore wear it could kill the cat? Even with the correct oil level?
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Tue 11 Jun 2002 08:09
Risk to cat - jc
Not just past the pistons-it can get thro' the crankcase ventilation system and be sucked into the intake manifold if the level is too high.There are phosphates in engine oil and these will eventually poison the cat if too many go down the exhaust.If a misfire is caused this will kill the cat.
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Tue 11 Jun 2002 16:52
Risk to cat - David Lacey
"So if the engine has bore wear it could kill the cat? Even with the correct oil level?"

Very much so, yes


MG-Rover Questions? Click on www.mg-rover.org
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Thu 13 Jun 2002 19:42
Risk to cat - Richard Turpin
As a matter of interest, during the fuel "strike" I had to put in 10 litres of 4 star. I assumed that It would damage the cat but the car (94 Previa 100,000 miles) passed the MOT recently. I did note however that the tester refused to open the engine compartment on the grounds that it's under the carpet etc, and therefore did not put his sensor in the dipstick hole as they normally do on other cars. Perhaps this has something to do with it. The car was main dealer serviced for the first 50,000 and since then (when I got it) has had nothing except pads, oil (fully synthetic every 5,000) filters,tyres, and wipers. Still on the original battery even!
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Thu 13 Jun 2002 20:40
Risk to cat - John S
Richard

The dipstick sensor is to measure oil temperature, as test should be done with oil (and therefore engine) hot. However, not using this probe won't affect the emissions reading. The test still appears to be valid even without the oil temp. being recorded.

Regards

John S
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Thu 13 Jun 2002 23:28
Risk to cat - David Lacey
£10-worth of 4 Star will not do the cat any long term damage to the cat at all

It might degrade its performance slightly, thats all.


MG-Rover Questions? Click on www.mg-rover.org
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