Could be technical, but applied to any (petrol) engine.
What should the oil in a hot engine of a petrol car smell like.
Unused, cold oil is fairly innocuous.
I ask because after a 30 mile trip when I check under the oil filler cap, the smell is quite aromatic. I wouldn't say petrol-like, but certainly more than I would expect. The oil (OE recommended Selenia) has been in the engine for 11 months and 8,000 miles.
Could I be right in guessing that some petrol is finding its way into the oil?
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8000 miles = overdue for a change in the opinion of many.
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What makes you think is if petrol, are there any other signs, like over fuelling at tick over poor petrol consumption, dirty exhaust, excessive gasses blowing when filler if and engine running. What makes you think it is the smell of fuel. Regards Peter
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I think the car's OK, but;
Unused, cold oil is fairly innocuous.
....when I check under the oil filler cap, the smell is quite aromatic.
I think you may need to seek some professional help for this oil smelling fetish you're developing! ;-)
Typically, if a car gets used on shortish journeys, then a certain amount of the heavier fractions of the fuel end up in the oil. Only after a longer journey with the oil hot for a long time do these begin to evaporate out from the oil.
However, if you were to try to completely outgas* a sample of used engine oil, I would suspect that you would have great difficulty.
* To do this outgassing, you would place a sample under high vacuum, and use a spectrometer to "sniff" the gas pmped out by the vacuum pump. This is a standard procedure for instrumentation going into high vacuum - whether earth-bound, or space-borne. There are lists available, published by NASA, of lubricants which don't outgas, but normal engine oil definitely isn't on the list!
The reason I think you would have great difficulty outgassing used engine oil is that the lighter fractions might come out quite quickly, but the heavier volatile compounds would probably only outgas very slowly indeed.
Or, leaving aside all the technical rubbish - you are always going to be able to smell petrol in used petrol engine oil to some extent.
Number_Cruncher
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On a less technical level than NC's interesting post, I would have expected the Red Baron to be an expert on the smell of oil as he flew his Fokker!
Jack
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Mine used to smell very 'petrolly'
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Hot oil smells, cold oil doesent. Fact of life.
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TourVanMan TM < Ex RF >
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Over my years as a mechanic I've met many women who like the smell of 'oily overalls'.
When I last visited the doctor, (straight from work), she mentioned the smell and told me that she liked it. Maybe a drop of gear oil in the right place would be more effective than hair gel or aftershave.
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Don't be so modest, None - Before everybody rushes off looking for the old Three-in-One, it seems much more likely to be your natural pheromones at work, post work, vide:
"The purest union that can exist between
a man and a woman is that created
by the sense of smell and sanctioned
by the brain's normal assimilation
of the animate molecules emitted
by the secretions produced by two bodies
in contact and sympathy,
and in their subsequent evaporation."
Source "The Perfume of Women and the Sense of Smell in Love"
Jack
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Don't tell SWMBO but I far prefer the smell of Castrol "R"........
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11 months and 8,000 miles implies quite a few short runs, perhaps? Lots of unburnt fuel in the oil as result. I'd be changing the oil every 6 months on that kind of useage.
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Pretty good response so far guys...
The engine did do a number of short journeys to begin with, but in the last few months has done daily commutes of 30 miles each way. So I think that the oil should really be outgassed, unless, of course, lighter hydrocarbon fractions are added in some way. Hence my query about the petrol.
I could go silly as I have regular access to FTIR (Fourier Transform Infrared analysis) to try to ascertain the various components in the oil. However, 11-month old oil will have a very different trace to new oil (I would need a comparison) and small fractions of petrol would also break down the oil itself.
My real concern is whether something like the piston rings or the bores are beginning to wear excessively and letting the petrol vapours to the oil? Would, if this did happen, also increase the consumption of oil as I have not yet detected this?
Yes, Union Jack - where I work I regularly get wafts of kerosene so I have good idea of that. We repair and overhaul fuel pumps for aircraft engines.
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Hot oil smells - There is no problem
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TourVanMan TM < Ex RF >
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