davedipster

Another oil question to add the many before...

Did an oil change @ 10miles and now only 3k later it's already very dark, is this normal? and is darkened oil knackered? surely after 3k it must still be ok.
The oil in my last car (honda CTR) didn't seem to darken so quickly, any ideas why?

Dipster

Vegescoob

Yup same with mine. Years ago I read that showed the oil was doing it's work and holding "stuff" in suspension. However as your Honda our 99 1.3 Micra I change oil 4.5K and it looks cleaner than Scoob at 3K.
Lots on here change at 3K some 2K and trackday fans often before and after each trackday.
Anyway oil is lots less than engine rebuild.

davedipster

Any idea what this 'stuff' is?
metal, carbon, air contaminants or just the heat of a turbo?
Do you think I would get less colouration using a different oil?

Cheers
Dipster

ALi-B

iTrader: (1)

Only real way of knowing is sending a sample off to an oil lab and get it tested - then you'll know exactly what is going on. (something I would love to do myself, testing with various oils to call an end to the great oil debate - if only I had the time )

Just a question though....before you changed the oil, how long had the oil been in there before you changed it to the current oil, and how many miles? Also how "black"?

If you had mucky oil before your oil change, then as soon as you pour some fresh oil in it will go black very quickly. It's not that the oil has got dirty all of a sudden, more so it's just mixed up with whats left of the old oil hanging round in the nooks and crannies of the engine.

And finally, how you been driving it (like a learner, like you stole it, or like you want to break it)? and what oil type (ester synthectic, synthetic or semi synthetic)?

Vegescoob

Really waiting for one of the oil experts to come along to say what exactly in "stuff" but I think as you say, perhaps apart from metal, hoping tiny metal particles are mostly in filter!
You don't say which oil you use. Do a search on here under oil and read. You will find this is hotly debated and ultimately you have to decide what make/grade to use in your car with reference to type of use, your driving and engine spec/mileage.

ALi-B

iTrader: (1)

Oh forgot to say, black stuff - usually oxidised oil particals in suspension. Not a problem really, it's something oil does as it ages/ is used. The question of if it needs changing is down to how long it's in there and how you drive moreso than the colour.

Dark Blue Mark

I can get oil analysed quite easily

Suspended particles are a combinations of things as per above, that are either disolved in the oil, or held in suspension. Anything begger gets caught in the filter media.

Bit of a tricky one on oil changes, you seem to increase the chance of an engine failure every time you change the oil in a classic scoob

MB

ALi-B

iTrader: (1)

True, damned if you do damned if you don't LOL

Although, I have a theory that scooby engines that fail just after an oil change didn't have much life left in them anyway so failure was inevitable. Problem of trying to prove that is rather tricky (and expensive).

Dark Blue Mark

Agreed....

MB

buzzard

the blackness is a combination of the "sheared" molecular chains of the oil due to friction and "cooking", particles of carbon and engine material and the effects of the added detergents.

knap

Typical UOA mix of M1 and Redline


Element Smpl Avg
Aluminum 3 5
Chromium 1 1
Iron 5 10
Copper 1 6
Lead 1 4
Tin 1 4
Moly 139 93
Nickel 0 0
Manganese 0 0
Silver 0 0
Titanium 0 0
Potassium 2 2
Boron 103 67
Silicon 5 8
Sodium 6 6
Calcium 2591 2143
Magnesium 12 113
Phosphorus788 778
Zinc 896 919
Barium 0 0

Visc@210 59.7 54-61
Flashpt 405 >365
Fuel% <0.5 <2.0
A/F% 0 0
Water% 0 <0.1
Insolubles0.3 <0.6

Vegescoob

I understand that but why in our examples does the oil from the Scoobys seem blacker than the longer mileage oil in the Honda /Nissan. Is it just that the Scooby engine is working harder cos of it's higher specific output than the others? Cos our Micra propably spends longer at higher revs than the Scoob.

davedipster

yeh, my CTR spent most of it's life bouncing off the limiter and it was 200hp, but the oil looked new after 3k.

Dipster

Dark Blue Mark

Heat is massively different past the turbo.

MB

aherridge

also becaus of boxer engie oil is working in a different way, has to travel further etc plus heat from turbo
you could try using a top fully synthetic oil bu to be honest regular changes is more adviseable, depends how hard your driving it

Dark Blue Mark

The motion of the pistons is the same so makes no odds. The heat is the key thing...

MB

Vegescoob

V interesting this. So are we saying the oil in turbo engine gets hotter, well logically must do? Subaru must consider overall though that oil temp is ok cos they don't fit an oil cooler as standard and I don't often see a cooler mentioned as a mod. My previous car Astra GTE 16v N/A had an oil cooler as standard.

ALi-B

iTrader: (1)

Scoobs do have a oil cooler as standard...an oil to water type - just above the oil filter if you look.

It also serves a handy purpose of heating the oil when cold as well as cooling it when hot

Dark Blue Mark

I dont think there is any issue here, as said, the oil will turn darker as it picks up contaminants and that's not neccasarily a problem. Its why the interval is 7.5k on classic scoobs, and about 10-15k on N/A cars.

Yes it will run hotter as it passes the turbo, and will be subject to coking in bad cases, if the oil isn't left to circulate afer a hard run. As its not a scavenge system, some of it will sit on the turbo when the car is off, and get a bit fried hence a cooldown period is a good thing, as is a very good grade of oil.

Not sure what their justification is on moving out the frequency on newer scoobs is though...

MB

Vegescoob

Oops. Ignorant little old me! I must look more closely next time underneath changing oil. That's the problem with no book manual available. Haven't got round to downloading one yet. Just wish Haynes would do one.

oilman

iTrader: (9)

Basically, if the oil is black then it's doing it's job. Some discolour more than others and synthetics tend in the main to be more efficient cleaners than others and can discolour quickly but this doesn't mean the oil no good.

Just pull out the dipstick and rub a sample between your fingers, it shouldn't be too gritty and shouldn't smell burnt.

Cheers
Simon

davedipster

Thanks for the info everyone.
I'll stick to my 5k changes, and using good old shell helix plus 10w-40 semi.

Dipster

Pavlo

Increased heat and cylinder pressure, leading to increased blowby and burning/blowing of oil off cylinder walls.

Paul

Dark Blue Mark

I blame it on the Flux Capacitor

Dave, Subaru do not specify a fully synth oil, but its widely regarded as better practice to use fully synth. Especially if its modded or you do track days.

MB