Burning oil or not

Thus spake john reid ( snipped-for-privacy@mail.invalid) unto the assembled multitudes:

If it's really white "smoke" then the car's in trouble - walk away.

Otherwise perhaps you are referring to water vapour ("steam" if you like), which you might get in cold weather. Water vapour disappears quickly; smoke will take much longer to disperse.

If it has been used for lots of short journeys or has been left standing about a lot, chances are that the valve gear might be corroded which might lead to improper seals and hence burning oil. It may also mean that the engine ran 'cold' for much of the time leading to oil emulsification and hence corrosion.

I'd always be deeply suspicious of an oldish car with low mileage.

Both scenarios are possible. An engine unused for a while can smoke when put back into use, things like piston rings get gummed up and don't really show their true colours until after a few heat cycles to free everything up.

Steve

"shazzbat" gurgled happily, sounding much like they were saying:

Add in a third scenario - it's almost certain to have been used by the proverbial one little-old-lady from new, to go to the shops and church once a week. It's probably rarely reached full working temperature, been touch-parked, and - if a manual gearbox - been regularly clutch-slipped at 4,500rpm and a slug's walking pace.

It may well be thoroughly shagged out as a result.

On Fri, 01 Oct 2010 14:37:58 +0100, shazzbat boggled us with:

Yes, this happened on my Puma. It had stood for a few months when I got it, and I was alarmed by it's oil consumption - over 3 litres in the first 500 miles, which were all around town. I caned it up to Manchester and back up the motorway, and it stopped using oil altogether.

It's much more likely in that scenario that it had been for lots of short trips, so what seemed to be the oil level was actually the "oil + condensation" level. Getting it nice and hot boiled all the condensation away.

If it really was using a litre in less than 200 miles, it would have been difficult to see the town...

Chris

On Fri, 01 Oct 2010 14:01:18 +0000, Chris Whelan boggled us with:

Well, it smoked quite a bit, oddly, I didn't notice it on the test drive. It was 9 years old when I bought it, with 92k miles, so it had done an average sort of mileage. I changed the oil the day after I bought it and kept an eye on it. After a 500 miles in a day thrash, it simply never used any again.

Chris Whelan gurgled happily, sounding much like they were saying:

Perhaps a tad dramatic. The engine in the 4x4 2cv was so fooked that it used a litre or so of oil in about 75 miles if you kept it on the second choke - on the m'way, f'rinstance - and strangely almost none if you kept it off the second choke. Anyway, it looked coal-fired from outside, apparently, but the smoke (exhaust came out under rear passenger door) just wasn't visible at all from inside, even if you were looking for it.

Maybe, but I've had old cars that used a pint in 500 miles, and smoked to the degree that they were only marginally legal.

Chris

If you were wanting to sell a car for a good price, you would have taken the car for a run and sorted out what the seller claims. If on the otherhand he is selling it for peanuts and it is just in his way then perhaps I would accept his comments. An 11 year old car generally has a cat which does not like oil vapours. Why did your friend not go for a longer run ?

Gio

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Chris Whelan saying something like:

Not necessarily. I recall a s**te old (new at the time) Marina 1.3 that burnt oil at the rate of 50~100 miles per pint and it wasn't all that smokey.

If it was doing 50 miles to the pint and not smoking much, either it was leaking, or someone was stealing it!

Chris

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Chris Whelan saying something like:

Nope. Burning it, on motorway legs. Round about town it didn't smoke at all.

It all depends on where the oil is getting into the air path. Inlet valves and piston rings will burn the oil quite cleanly in a high temp petrol fueled combustion. Oil post combustion is into exhaust and has very much less chance to burn fully as there's little oxygen.

When a destroyer makes smoke it doesn't add more fuel to the boilers but into the exhaust stack.

That's why a redex treatment or blown turbo turbine seal is so good at making smoke.

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Peter Hill saying something like:

Exactly. I could certainly smell the burning oil, but it was near invisible. The engine got howked out and sent back to BL under warranty.