what oil does everyone use?

[MH3.0R]

I could get 25K from the engine oil easily,

So all the carbon and sh!t that build up in teh engine is happily stuck in your bearings and oil galleries as opposed to being suspended i the oil.

i WANT an oil to go black quickly, i'm then confident that the detergents are doing their job at removing the crap from my engine.

Redline is probably OK for race motors that are pulled apart frequently where the detergents are not required.

just my opinion
no need to spend that sort of money on oils in a road car

Is this opinion supported by the mechanical engineering fraternity? It is a new line of thought for me and I am interested to pursue the structured thinking and evidence that supports this point of view. Not least of which, I may be able to prolong the mechanical life of my engine, transmission and diffs by using lower spec lubricants.

[teK--]

For a mostly daily driver, using an "everyday" oil that is changed regularly is more beneficial than using high end oils but leaving them in the engine for extended service intervals.

The only time I would see a high end oil (Group IV/PAO or Esters) as being required is if you are using the car under extreme heat/cold/load conditions, e.g. regular heavy towing or high RPM track use, if you live in a desert etc.

[MH3.0R]

Would city start / stop traffic on a daily basis be considered high load condition? I thought the service intervals are reduced to cater for a high proportion of city stop / start driving. I recall somewhere in the doc that under harsh conditions, the regular service interval period should be reduced and that city driving is considerd harsh. About 50% of my driving, daily would be in the harsh category, so as a long term keeper, am I doing the wrong thing, or over doing the right thing? The Redline product is commented in several places to have one of the best base oil specs.

On top of the good base oil, I am also using one of the better filters (which do hold a significant volume of fine and course crap) also aimed at reducing engine wear.

Am I really on the wrong path here?

[teK--]

City stop/start traffic is considered harsh use, so you would service more regularly than a car that gets to stretch its legs out in free flowing or fast highway traffic.

Also repeated short trips is in the same category. I'm in this one my drive to work is less than 15mins the engine oil only really just gets up to temp a few mins before I get to work. I replace my oil and filter every 6-8 months or 6-8,000Kms whichever comes first.

Redline is a good base oil (group IV if I recall correctly) but is overkill for a daily driver. Better off with a good quality group III "synthetic" oil such as Castrol Edge (5W-30; their 0W-40 is a true group IV but expensive and too thin for our engines), Penrite HPR etc which is much cheaper.

If you have lots of money to burn then this does not apply, continue using Redline or I would recommend Amsoil which is one of the best value group IV true synthetic oils you can buy.

[Robbks]

Is this opinion supported by the mechanical engineering fraternity? It is a new line of thought for me and I am interested to pursue the structured thinking and evidence that supports this point of view. Not least of which, I may be able to prolong the mechanical life of my engine, transmission and diffs by using lower spec lubricants.

If you read between the lines..
http://www.castrol.com/castrol/sectiong ... Id=7022949
"Castrol Non–Detergent Motor Oil is formulated from highly refined and high viscosity index, paraffinic base oils.
They meet the requirements of API Service Classification SB.
This classification does not meet current engine manufacturers' warranty requirements. "

This is because the leftover carbon deposits in the engine will clog the rings, vlave stems, oil galleries, etc, etc and increase wear rates

the actual detergent additive in oil (Zinc Based) is also the last lineof defence against metal on metal wear within an engine.
when the oil film shears (from excessive heat, stress, etc) the zinc based compound attaches to the bare metal surfaces to provide some form of lubrication/ protection (remember how good Leaded [zinc] containing petrol was.)
Lead/ Zinc is a great lubricant. grab an old fishing sinker, rub it over two bits of metal and see how easily they slide on each other as compared to without it..!

(oh forgot to add, 3 years of mechanical engineering/ fluid dynamics study did give me some interesting facts and reading to do )

[josho]

such as Castrol Edge (5W-30; their 0W-40 is a true group IV but expensive and too thin for our engines).

is the 0w-40 too thin? or the 5w-30? or both?

[Dropz]

5W-30 meets Subaru specs for all their petrol engines, turbo, non-turbo and 6 cylinder.

0W-40 is for the NEW FB family Subaru petrol engines.

[josho]

Sweet, i think for now ill keep using edge sport 5w-30, at least for a couple more services. once my car gets up to around 160-170k i think ill make the switch to something slightly thicker.

[MH3.0R]

Is this opinion supported by the mechanical engineering fraternity? It is a new line of thought for me and I am interested to pursue the structured thinking and evidence that supports this point of view. Not least of which, I may be able to prolong the mechanical life of my engine, transmission and diffs by using lower spec lubricants.

If you read between the lines..
http://www.castrol.com/castrol/sectiong ... Id=7022949
"Castrol Non–Detergent Motor Oil is formulated from highly refined and high viscosity index, paraffinic base oils.
They meet the requirements of API Service Classification SB.
This classification does not meet current engine manufacturers' warranty requirements. "

This is because the leftover carbon deposits in the engine will clog the rings, vlave stems, oil galleries, etc, etc and increase wear rates

the actual detergent additive in oil (Zinc Based) is also the last lineof defence against metal on metal wear within an engine.
when the oil film shears (from excessive heat, stress, etc) the zinc based compound attaches to the bare metal surfaces to provide some form of lubrication/ protection (remember how good Leaded [zinc] containing petrol was.)
Lead/ Zinc is a great lubricant. grab an old fishing sinker, rub it over two bits of metal and see how easily they slide on each other as compared to without it..!

(oh forgot to add, 3 years of mechanical engineering/ fluid dynamics study did give me some interesting facts and reading to do )

Thanks for that. It is good to see some cred behind the comments to differentiate them from "opinion". Are you able to comment on the effects / impacts of higher quality "base" oil for synthetics?

I also know precisely what you say about old fishing sinkers as I used to use them. They can be slippery little suckers.

[Robbks]

Synthetic oils are basically engineered to provide oil molecules of the exact same size, or a combination of sizes as requied by the application.
Consistently sized molecules generally circulate/ flow better and provide a higher "film strength" due to the evenly sized molecules lining up and stacking evenly
Think of oil molecules as a bunch of ball bearings in a shallow container. if they're all the same size they all line up in rows neatly and pack tightly against each other, but the entire amount of them also roll freely as one within the container.

Manufacturers will also incorporate a different size molecule aswell (usually a much smaller one) that would perfectly "fill the gaps" between the larger molecules.
this allows an even higher film strength, but still keeping the high flow proeprties that is desired.

Synthesising oils also removes the very, very small molecules that are small enough to get past the rings/ valve seals, etc and be burned in the combustion process.
burning excess oil creates excessive carbon deposits in the engine, lowers the effective RON of the fuel and causes the car to use oil.
when an oil gets old and dirty and the molecules begin to break down, they get past the rings and are burned more easily, and the oil consumption increases noticibly.

Standard mineral oils have a range of different sized molecules which does have it's benefits as there will always be a molecule of the right "size" to "fit" where it's needed.
but they don;t usually have the inherent film strength of the synthetic.
and teh semi-synth oils (such as my favourite, Magnatec) are a blend of both and IMHO offer the best of both worlds for a street car
they have higher film strength, but also the range of molecule sizes to protect everywhere. and they're usually much more affordable than fully-synth oils.

[Kekotic]

Rob how long do you run with car with the diesel oil?

[Robbks]

I just put it in for one standard oil change interval which in my case is 5000km anyway,
as my cars do a lot of short city trips, or the highway and country runs are usually "spirited"
more frequent oil changes are a good thing, and really are only $50 a time. (oil, filter, Upper Engine Cleaner)

[teK--]

Good summary Rob

There is a lot of lies in marketing re synthetic/mineral oils.

E.g. Ultra refined hydro cracked Group III (mineral) oils (such as Edge 5W-30, or blends such as Magnatec) are being marketed as "synthetic" despite being pumped out of the ground, but due to a loophole in the definition of "synthetic", these oils continue to be marketed as such. Mobil was in a huge legal battle once because they didn't like other manfacturers marketing a "synthetic" oil at much lesser price than their real synthetic Mobil 1.

Only Group IV (also referred to as PAO) and Ester oils are technically man made from scratch.

[Kekotic]

Removed.

[teK--]

Can't remember what colour bottle it's in but Mobil 1 is group IV oil.