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#3204165 - 12/02/13 05:32 PM Diesel oil drain -- black, more questions
Raven Offline


Registered: 11/17/13
Posts: 10
Loc: Morro Bay, CA
Hi there,

Been wanting to ask these questions, particularly the first two, for quite some time (like nearly 10 years):

1.) I used to work as a lube tech. Diesel passenger pickup trucks had to be filled up to about 14qts of engine oil. We would start the engine up to conduct a basic pressure test, and then once in awhile we might have to drop half a quart or so. But why does the oil go in yellowish, yet in that 30 seconds, come out black like it's been used?

People have given me a number of theories, but no real explanation -- such as "It's dirty inside and it's picking up contaminants." ??? If it was that dirty inside, how could it even run? Crank bearings, valve guides, piston rings, hydraulic lifters, tensioners etc would be TOASTED.

The rest of these questions are more generic, but I don't want to create additional threads for relatively easy questions.

2) At the typical running temperature of an engine, which is about 190-200 deg F, if I am running 20W-50, what might be the "viscosity" of the oil right then and there? 50 weight? 40 weight? 45? 30? What about 10W-40 -- might it be maxing out at 40 weight?

3) I have run Castrol GTX (non high mileage) for all my prior BMWs and my present 'yota. Is it "decent"? "Good enough"? I just put in 10W40 in the 'yota (1991 2WD pickup with the 2.4L 22RE mill) and I heard that that is *bad* for that motor. (I used 20W-50 in all the BMWs, they were E30 325e, 325i and 325is models.)

4) One last real off-topic question. If I run aftermarket lights, can't I be stopped by LEOs to make sure the lights are DOT/SAE rated? If they don't have DOT/SAE markings, am I supposed to carry paperwork to prove that they are rated as such?

Thanks!


Edited by Raven (12/02/13 05:34 PM)

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#3204186 - 12/02/13 05:45 PM Re: Diesel oil drain -- black, more questions [Re: Raven]
Cardenio327 Offline


Registered: 11/30/09
Posts: 476
Loc: Oaxaca, Mexico
1.) Yes, diesel engines are that dirty inside. The instant black is fine carbon and soot, mostly harmless, think black dye.

2.) 190 F to 200 F is the territory of Xw-20 and Xw-30 oils. Xw-40 is a bit on the heavy side for these temperatures, Xw-50 too heavy in my opinion.

Some Ford Rangers run around 225 F on 5w-20 and some Corvettes run about the same temp on 5w-30.

3.) 10w-40 GTX is fine for your Toyota. I would probably use 5w-30 or 10w-30 instead and save the 10w-40 for your BMWs.

4.) I have no idea, but I would assume if it does not have DOT markings it is illegal no matter what the paperwork claims.
_________________________
'08 Honda C90ST Super Cub 5w-50 M1EP
'08 Honda NX4 Falcon 5w-50 M1EP
'09 Honda Fit LX 10w-30 QSUD
'99 F-150 W/T 4.2L 10w-30 QSUD

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#3204200 - 12/02/13 06:00 PM Re: Diesel oil drain -- black, more questions [Re: Raven]
JR Offline


Registered: 08/08/04
Posts: 920
Loc: Michigan born but my heart bel...
Answer to question one is from what i have been taught is soot from the cumbustion of diesel fuel. my 84 rabbit i had would to turn oil so dark that you couldn't see the stick in just a minute of runtime.

ken

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#3204203 - 12/02/13 06:07 PM Re: Diesel oil drain -- black, more questions [Re: Raven]
Garak Offline


Registered: 12/05/09
Posts: 11182
Loc: Regina, Saskatchewan, Canada
Originally Posted By: Raven
4) One last real off-topic question. If I run aftermarket lights, can't I be stopped by LEOs to make sure the lights are DOT/SAE rated? If they don't have DOT/SAE markings, am I supposed to carry paperwork to prove that they are rated as such?

DOT compliance in that regard tends to be self-regulated. Depending on the jurisdiction, yes, one could get a ticket for that.
_________________________
Plain, simple Garak.

2008 Infiniti G37 coupe - Mobil Delvac 1 ESP 5w-40, Hastings LF113
1984 F-150 4.9L six - Quaker State GB 10w-30, Wix 51515

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#3204238 - 12/02/13 06:56 PM Re: Diesel oil drain -- black, more questions [Re: Raven]
earlyre Online   sleepy


Registered: 11/22/11
Posts: 2128
Loc: Lima, Ohio, USA
also to add to the answers to #1:
It could be from residual oil that didn't get fully drained out. unless you were letting 'em drain for days @ a time....
_________________________
Mine:
09 Mercury Sable : Meijer(Warren)Full Syn 5w20, FL400s
Mine to Maintain:
03 Pontiac Vibe : PP(old) 5w30, Fram Ultra XG4967

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#3204254 - 12/02/13 07:08 PM Re: Diesel oil drain -- black, more questions [Re: Garak]
Raven Offline


Registered: 11/17/13
Posts: 10
Loc: Morro Bay, CA
I do appreciate the responses =)

1) So the soot on the inside, the oil is thusly designed with more additives to keep the soot in suspension, and with more detergents, for diesel engines? Is it fine enough that it doesn't cause problems with bearing surfaces like the soft crank bearings or the OHV rockers which are under considerable stress?

2) So the xW-YY weight on the YY is a function therefore of engine age and design (older engines, more worn out engines) and not so much based on working temperature? The reason I'm thinking is that a 1OW-30 would be desireable over a 20W-50 if when it is hot, doesn't "need" any additional "weight" over 30. That's why I posed the question asking about what "weight" it might be at operating temperature.

I don't own any of the BMWs any more but both of the 325i models had oil coolers. (The 325e and the 325 "super eta" don't have them, I forgot if the Euro-only 323i had one I don't think it did, and neither did the 320i. They all use the same block [different bore though] but have different heads, pistons, con-rods and cranks. The E30 ///M3 also has an oil cooler.)

Should I run the engine on a trip long enough to get it hot, then drop about 1/4 liter then stick a thermometer in it? (or pull the valve cover I guess, there's always a small pool of oil underneath the front of the cam) The 'yota has no oil temp gauge.

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#3204273 - 12/02/13 07:23 PM Re: Diesel oil drain -- black, more questions [Re: Raven]
fdcg27 Offline


Registered: 09/25/09
Posts: 9191
Loc: OH
Many diesels load the oil with soot in a very few miles.
The oil I drained our of my 123 diesels was always jet black and had a very distinctive scent.
GTX is okay stuff in any engine.
I doubt that this four cylinder Toy really needs 10W-40, but it won't hurt anything. 20W-50 was all the rage in the OM recommendations of old German cars. It may not have been needed than and isn't needed now. I use 10W-40 in my old BMW for which the OM recommends 20W-50 for summer temperatures.
Finally, I can't imagine a cop actually stopping you for paperwork on a set of running lights, since they aren't required equipment to begin with.
_________________________
12 Accord LX 22K HGMO 0W-20
09 Forester 64K PU 5W-30
02 Accord 127K G-Oil 5W-30
01 Focus ZX3 98K Synpower 10W-30
95 BMW 318iC 146K Defy 10W-40

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#3204285 - 12/02/13 07:39 PM Re: Diesel oil drain -- black, more questions [Re: Raven]
A_Harman Offline


Registered: 10/01/10
Posts: 4108
Loc: Michigan
Originally Posted By: Raven

2) At the typical running temperature of an engine, which is about 190-200 deg F, if I am running 20W-50, what might be the "viscosity" of the oil right then and there? 50 weight? 40 weight? 45? 30? What about 10W-40 -- might it be maxing out at 40 weight?



The last two digits in an oil's viscosity number is the high temperature rating, which has definite ranges that are defined by the SAE, and have to be measured at 100C (212F). As temperature goes higher or lower than 212F, it is not appropriate to say that the oil viscosity grade is changing, because the viscosity grade is defined only by the measured viscosity at 212F. Yes, the oil's actual viscosity is changing with temperature, but the SAE doesn't define what the viscosity has to be at other non-freezing temperatures.

If you want to estimate what the actual viscosity of your oil is at any operating temperature, you need to have the oil kinematic viscosities at 40C and 100C from its spec sheet, and then plug those values into a viscosity calculator, such as Widman's.
_________________________
1985 Z51 Corvette track car
2002 Camaro Z28 LS1/6-speed
2001 Dodge Ram 2500 diesel
1972 GMC 1500 shortbed project truck

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#3204291 - 12/02/13 07:51 PM Re: Diesel oil drain -- black, more questions [Re: Raven]
Tegger Offline


Registered: 03/20/06
Posts: 1394
Loc: Canada
Originally Posted By: Raven
If I run aftermarket lights...If they don't have DOT/SAE markings, am I supposed to carry paperwork to prove that they are rated as such?

It's been a while since I had to deal with this sort of thing but, way back when,
1) if the lights were DOT-legal, it said so on the lens, and
2) if the lights were not DOT-legal, you were supposed to keep them covered when you were on a public highway. Non-DOT lights sometimes came with sewn fabric/vinyl or rigid-plastic covers for use "on road".

If your non-DOT lights are not lit but are uncovered, you're probably unlikely to get stopped by a cop unless he's bored or is a jerk. Probably depends on jurisdiction, too.
_________________________
1991 Acura Integra - 414,467 miles - Mobil 1 5W-30, Honda OEM filter - **SOLD**
2013 Toyota RAV4 - 15,000 miles - Toyota 0W-20, Toyota filter

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#3204416 - 12/02/13 09:38 PM Re: Diesel oil drain -- black, more questions [Re: Tegger]
Raven Offline


Registered: 11/17/13
Posts: 10
Loc: Morro Bay, CA
Maybe if I have to do some kind of science experiment or study I could buy up some popular grades of oil and see how the viscosity changes versus temperature.

Just how much soot is allowable in a diesel oil? By the assertion above, it's not really harmful, so it's probably nothing to worry about. Is it usually byproducts of blow-by (hey, run a 20:1 compression ratio and you eventually get it no matter what) or does it come off the cylinder walls, or ????

fdgc27, your 318i probably has the M44 engine, which was desecended from the M42, which came from the M40, which probably came from the M10. The M10 early on had a dual-row timing chain and was said to be pretty robust indeed. Came with either carburettor (the 316*, as the 316i and 318i all had Bosch K or L Jetronic) or fuel injection, 1.6 or 1.8L. The M40 was only sold in Europe IIRC, as the 318i American version stopped in ... oh, '85 or thereabouts and didn't come back until I think 1990 with the 1990 & 1991 318i/318iS with the M42. I'm told the M40 has noisy lifters and is the anchor for the BMW's executives' yachts. The M42 is pretty good with DOHC but back when I was in the E30 game (2004 to 2011) I caught an example (on that foul-mouthed r3vlimited site) of a M42 which had destroyed its timing chain. Bits of chain all over the innards and was a mess. (Probably about as bad as the guy on Bimmerforums who lost his oil cap and put a sock in it's place, only to shortly thereafter wrap the whole sock around his nice M50 or M52 exhaust camshaft. Ooops.) Ideally if I was build my favorite E30 it would be a 318iS (because I hate sunroofs) with rear window mod (the airbag 1990 and 1991 models don't have rear opening windows on the coupes) and all that with a S50B32 Euro spec motor (3.2L @ 321hp) with the E46 6spd tranny.


*: The 316 and 316i weren't sold in the USA at all, I forgot where it was sold, I think it was for markets like Greece. The 316 actually has a twin barrel mediocre carb, FWIW. I actually drove a grey-market import 324d, which was a Euro-only model, 2.4L non-turbo diesel with an automatic (!!) and not a single option of any kind. Funny because about 5 months afterwards, some chap in LA pokes up on the Bimmerforums E30 section and asks about vegetable oil conversion HAHAaaaa and what do you know it's the same green 1986 four-door 324d I drove. Small world...

/end BMW talk smile

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#3204489 - 12/02/13 10:45 PM Re: Diesel oil drain -- black, more questions [Re: Raven]
blackman777 Offline


Registered: 01/08/13
Posts: 981
Loc: Santa Ana, California
Originally Posted By: Raven
Just how much soot is allowable in a diesel oil? By the assertion above, it's not really harmful, so it's probably nothing to worry about.

Soot is harmful to an engine. That's why you're not supposed to run regular gasoline oil: It is Not designed to capture the soot & protect the engine. (Although it's usually okay for ancient 1980s/CF-rated engines.)

In a modern diesel most of the soot is probably picked-up as it passes through the turbo & gets exposed to exhaust.

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#3204490 - 12/02/13 10:45 PM Re: Diesel oil drain -- black, more questions [Re: fdcg27]
Garak Offline


Registered: 12/05/09
Posts: 11182
Loc: Regina, Saskatchewan, Canada
Originally Posted By: fdcg27
Finally, I can't imagine a cop actually stopping you for paperwork on a set of running lights, since they aren't required equipment to begin with.

Well, it would be a good excuse to nail someone if he really wanted to do so. If they're not approved for highway use, then they are for off road use only, and hence the ticket. But it would take a pretty unique set of circumstances to get checked that in depth.

Tegger covers it correctly. If someone wants to write you a ticket, he'll find a way, including the DOT issue, a loose battery tray, windshield/window decals, you name it. I wouldn't worry. If they're bright or obnoxious, keep them off when there's oncoming traffic. wink
_________________________
Plain, simple Garak.

2008 Infiniti G37 coupe - Mobil Delvac 1 ESP 5w-40, Hastings LF113
1984 F-150 4.9L six - Quaker State GB 10w-30, Wix 51515

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#3208204 - 12/06/13 07:45 AM Re: Diesel oil drain -- black, more questions [Re: Raven]
ac_tc Offline


Registered: 05/06/08
Posts: 512
Loc: sweden
Theres a reason that soot is used in paint, black paint.
Its a powerfull colour agent so the black new oil is basically dyed, theres wery little soot in it- no worries.
Or if you are really worried- do three oilchanges in a row with the engine idled for a minute or two between changes.....
_________________________
-98 Dodge Durango 5.9 4*4 HDEO 10w- 40 ci4
-04 PT Cruser GT 10w- 40 HDEO ci4
-Everything else HDEO 10w- 40 ci4/STOU 10w-30/THF

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#3209898 - 12/07/13 09:03 PM Re: Diesel oil drain -- black, more questions [Re: earlyre]
y_p_w Offline


Registered: 05/06/05
Posts: 2312
Loc: SF Bay Area
Originally Posted By: earlyre
also to add to the answers to #1:
It could be from residual oil that didn't get fully drained out. unless you were letting 'em drain for days @ a time....

Even with that there are probably places in the engine and oiling system where oil will continue to remain unless sucked out with a vacuum or sponged off.

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#3210398 - 12/08/13 12:48 PM Re: Diesel oil drain -- black, more questions [Re: Raven]
bullwinkle Offline


Registered: 10/09/04
Posts: 3978
Loc: Cincinnati, OH, USA
Inside of a diesel engine has black fine soot everywhere, diesel oil additives cause it to "agglomerate" or clump up so it can be caught by the oil filter. That's why semis (& aftermarket systems for light duty diesels) have centrifugal and bypass filters to help get excess soot out of the oil & run it longer, verified by UOAs (of course).
_________________________
06 Ram 3500 CTD 4X4 48RE SRW, 93 GMC C3500 6.2 diesel, 89 F-450 7.3 IDI, 98 Cherokee 4.0, 05 Scion xB, 82 Mercedes 300D, company van 12 Ford E-250 4.6

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