Re: engine oil, warming up the car

"Ray O" <rokigawa@tristarassociatesDOTcomn> wrote in message
news:4aeaa$4425d5b3$180fead6$13482@msgid.meganewsservers.com...[color=blue]
>
> "Nicholas Bourne" <nabourne@tpg.com.au> wrote in message
> news:4425cea9@dnews.tpgi.com.au...[color=green]
>> The engine oil is easy, just use the correct oil wight listed for your
>> expected climate temparture range and the correct grade for your car. As
>> for brands I have seen cheap brands out perform expensive brands on oil
>> tests so just pick one you are comfortable with and change it regurally.
>> I always change mine at 5000kms but I do a lot of city driving and mine
>> gets
>> contaminated quickly, my dad does the same but he has a high revving
>> motor that stresses the oil more.[/color]
>
> Whatever brand oil you use, it should have an API SL rating.
>
> I'm no expert on oil, but I doubt if it gets "stressed."[/color]

Oil does get "stressed", but that is not the full technical explanation. If
you want to get into the physics involved in an engine I'm more than happy
to but I didn't feel this was the time or the place for it, I was just
trying to give an answer to a question. There is a lot of stress put on the
rotating components of a engine the little end rod bearing get the highest,
at the point of piston direction reversal there is a lot of inertia in the
piston that has to be overcome and the ability of the oil to maintain a
constant oil film on the bearings is paramount. that said like most things
oil and it's additives degrade when placed in an environment where they are
subjected to stress and high temperatures. I have based what I said above on
my experience as a Analytical Chemist and my dads previous experience as a
race mechanic.

For the record my dad and I both use a Penrite HPR15 semi-synthetic oil with
a 15W-60 weight and a API SM/CF rating. this oil performs the best of the
oils we have tried in our budget, it suits our climate, it never gets below
10 Celsius here but can it get into the high 30's. I can get better oils
such as Royal Purple but I cant justify the $80 per litre price tag. In
5000km the oil goes from a nice dark honey colour to a tar black. If that is
not oil degradation I'm in the wrong profession.
[color=blue][color=green]
>>
>> As for the warm up just start the car and drive, dont use full throttle
>> and high rpm if you can avoid it untill the temp guage starts to move but
>> after that you are fine. If you have ever seem a F1 car warming up the
>> motor nerver stays at one rpm point or throttle setting for more than
>> about 2 seconds. To hear it you would tink someone is in the car just
>> reving it for the hell of it but it helps heat all the motor componets
>> evenly. There has to be something in that if they are willing to do that
>> to a 20000rpm capable motor that costs $100000+ insted of letting it idle
>> to warm up.
>>[/color]
>
> The reason drivers rev the engines so high on competition engines is that
> they do not idle well. Nothing to do with heating all motor components
> evenly. Cam timing is set for high RPM, not idle so they would stall
> unless revved up.[/color]

Idle speed for F1 engines in particular has little to do with cam timing,
they idle so high because they have extremely small flywheels and very low
mass internals. A standard 12-14 inch cast flywheel would disintegrate at
20000rpm and 1.5L V8 has small pistons than your average lawnmower. When you
have computer controlled hydraulic valves the operating range of the cam is
superfluous to where the motor idles. V8 supercar motors in Australia run
7500rpm make 700hp from a five litre pushrod v8 and they still idle
perfectly at ~1000rpm, a F1 motor may need to idle at 3000rpm to be smooth
but that is a hell of a lot lower than peak power at 20000rpm. Their idle
speed is still a small percentage of what the motor can rev to. They rev the
motor to reduce warm-up time and damage that sitting and idling does do to a
cold race motor. I street motor does not get damaged anywhere near as much
but it still happens, otherwise the manuals would tell you to sit and idle
the car for a set warm-up time.
[color=blue]
> --
>
> Ray O
> (correct punctuation to reply)
>[/color]

"Huw" <hedydd[nospam]@tiscali.co.uk> wrote in message
news:48m5l3Fkg76dU1@individual.net...[color=blue]
> Nicholas Bourne wrote:[color=green]
>> "Ray O" <rokigawa@tristarassociatesDOTcomn> wrote in message
>> news:4aeaa$4425d5b3$180fead6$13482@msgid.meganewsservers.com...[color=darkred]
>>>
>>> "Nicholas Bourne" <nabourne@tpg.com.au> wrote in message
>>> news:4425cea9@dnews.tpgi.com.au...
>>>> The engine oil is easy, just use the correct oil wight listed for
>>>> your expected climate temparture range and the correct grade for
>>>> your car. As for brands I have seen cheap brands out perform
>>>> expensive brands on oil tests so just pick one you are comfortable
>>>> with and change it regurally. I always change mine at 5000kms but I
>>>> do a lot of city driving and mine gets
>>>> contaminated quickly, my dad does the same but he has a high revving
>>>> motor that stresses the oil more.
>>>
>>> Whatever brand oil you use, it should have an API SL rating.
>>>
>>> I'm no expert on oil, but I doubt if it gets "stressed."[/color]
>>
>> Oil does get "stressed", but that is not the full technical
>> explanation.[/color]
>
> It suffers shear and heat stress to varying degrees according to the duty
> cycle and the particular engine.
>
> If you want to get into the physics involved in an[color=green]
>> engine I'm more than happy to but I didn't feel this was the time or
>> the place for it, I was just trying to give an answer to a question.
>> There is a lot of stress put on the rotating components of a engine
>> the little end rod bearing get the highest, at the point of piston
>> direction reversal there is a lot of inertia in the piston that has
>> to be overcome and the ability of the oil to maintain a constant oil
>> film on the bearings is paramount. that said like most things oil and
>> it's additives degrade when placed in an environment where they are
>> subjected to stress and high temperatures. I have based what I said
>> above on my experience as a Analytical Chemist and my dads previous
>> experience as a race mechanic.
>> For the record my dad and I both use a Penrite HPR15 semi-synthetic
>> oil with a 15W-60 weight and a API SM/CF rating. this oil performs
>> the best of the oils we have tried in our budget, it suits our
>> climate, it never gets below 10 Celsius here but can it get into the
>> high 30's. I can get better oils such as Royal Purple but I cant
>> justify the $80 per litre price tag. In 5000km the oil goes from a
>> nice dark honey colour to a tar black. If that is not oil degradation
>> I'm in the wrong profession.[/color]
>
> Sounds more like pollution than degradation to me.
>
> Huw[/color]
It's a bit of both. Blow past does pollute the oil but the major part of
that is unburnt fuel which vaporises off if the motor is at operating
temperature the rest includes carbon and a few other nasties. This does
pollute the oil but not at the rate that would colour oil that quickly. Most
of it is oil breakdown products which are highly coloured, a bit like
blacking of wood when it is burnt. This is also why the crankcases of
engines are black inside. The oil does contain surfactants to remove this
but to really clean it off you need to scrub with a high concentration of
detergent, or acid dip the block which will also remove the lime scale from
the water galleries.

Nick.

Nicholas Bourne wrote:

[color=blue]
> It's a bit of both. Blow past does pollute the oil but the major part
> of that is unburnt fuel which vaporises off if the motor is at
> operating temperature the rest includes carbon and a few other
> nasties. This does pollute the oil but not at the rate that would
> colour oil that quickly. Most of it is oil breakdown products which
> are highly coloured, a bit like blacking of wood when it is burnt.
> This is also why the crankcases of engines are black inside. The oil
> does contain surfactants to remove this but to really clean it off
> you need to scrub with a high concentration of detergent, or acid dip
> the block which will also remove the lime scale from the water
> galleries.
> Nick.[/color]

There must be some bloody awful designs of engines where you are, or the
petrol is filthy, because over 30 years I have never come across an engine
of mine that actually colours the oil worse than milk toffee brown in 6000
miles and even the old Austin/MG Montego 2litre and Range Rover V8 changed
at 12000 miles were no worse although the V8 could suffer from varnish if
inferior oils were used.
The only one I do know of is a V8 Land Rover of my neighbour's which did not
have an oil change for 35000 miles and which did sieze up due to black,
tarry sludge.

Some diesel engines blacken their oil within minutes of a fresh change of
oil but still work well up their recommended oil change interval which, for
mine, vary between 5000 miles [an old Land Rover] to 15000 miles [new Range
Rover diesel].
I do not get the ambient temperatures you do.
If left for too long with API CF4 or first level SHPD oil the LR oil
thickens due to carbon saturation at 5000 miles although with a second tier
SHPD [API CH4 or more pertinently one that meats ACEA E3 or mb228.3] then it
stays in grade for much longer with no apparent thickening at 5000 miles.

I have another diesel which is air/oil cooled, turbocharged and intercooled,
which is used sometimes at full load and full revs for days on end. It runs
very hot and the lower cylinder and under-piston area is cooled by the oil
which gets extremely hot. In this engine a combination of heat and shear
stress causes sudden viscosity breakdown at a certain point which can be
only a few hours use more than the recommended oil change interval. The
symptom is easy to recognise because the engine will start consuming vast
quantities of oil quite suddenly due to thinning even though it looks quite
clean enough, and consumption will return to negligible quantity as soon as
an oil change takes place. The vicosity just breaks down. This is a well
known phenomenon where engines are run to their limits and modern oils can
result in slightly extended service intervals and safer running with less
wear.

Huw