zwede

I went 7k miles before changing oil and sent a sample in for analysis. Here are the results:

Oil: Mobil 1 10W30
Filter: AC Delco PF35
Total mileage: 103k. Miles since rebuild: 30k.

------------------------------

Oil weight within spec: Yes
Water contamination: No
Fuel Contamination: No
Antifreeze Contamination: No

Levels (A=acceptable, B=Borderline, C=Critical)
Chromium: A
Copper: A
Iron: A
Lead: A
Tin: A
Aluminum: A

Chromium and Aluminum indicates air filter working and no abnormal conditions in pistons or rings.

Copper and lead indicates no problems with bearings.

Conclusion: No internal wear found. Continue current maintenance schedule.

-----------------------------
So it seems the oil is still fine after 7k miles.

I got the analysis kit at autozone. It is done by Titan labs. Pretty neat setup. I paid $18.95 and kit comes with the bottle and prepaid postage box. I just took the sample, threw it in the mail box and had the results about 5 working days later.

Jughead

So are you saying that the oil change wasn't necessary using Mobil 1?

zwede

That's what it looks like. I'm thinking of going 10k miles and send it in again. I know of some people on a mailing list that go 15k miles in the C5's between oilchanges and analysis comes back perfectly normal.

In my opinion the 3k miles or 3 months is a scam by the quick change franchises, and not based on any engineering ground.

flood

Depends on the engine. That is reassuring though. I have thought about using mobile 1 for a while.

I wonder what the results would have been using a regular oil instead of synthetic?

Tom454

So... based on the test results... the oil was exactly as pure as it was when you poured it in... with absolutely no contamination. ??

Did you pour some used oil into a clear glass container and compare it to fresh, unused oil? Was there a difference? According to the test, the answer is no... no difference. Is there something wrong with this picture?

Not questioning your personal integrity, so don't get defensive... but there is something missing here... maybe you can educate us?

I have done the "visual" test after only 3000 miles, and the synth is equally as black as dino at that mileage. Help me out here.

Tom

Edit... my test was on a fresh rebuild of a 1987 Ford factory roller cam 302 fuel injected engine. No dino oil had benn installed. My rebuilt engines are super clean... beyond ****. After 500 miles, I dumped the synth and installed fresh synth. This eliminated any break-in contamination. After 3000 miles, it was black.... just like dino oil.


[Modified by Tom454, 1:05 PM 1/17/2002]

bence13_33

Tom:
This may sound like a "newbie" question but why does oil turn black? My educated guess is because of some sort of contamination. Just curious.

Tom454

bence... I guess that is the "big question"...

If someone (an expert) can provide a systematic, logical, no BS (no hear-say, no guesses) answer... then I may become a "believer" along with zwede and the rest of the synth crowd... I wanna believe, I really do. :)

Tom

JB

I believe the temperature changes the oil's chemical composition, which is why it darkens, not because of comtamination--but obviously it doesn't affect the lubrication characteristics given the analysis results (at least not in 7000 miles).

But, Tom, that's just unsystematic, illogical, BS-ful, hear-say guessing :D

JB

'78SA


[Modified by JB, 12:50 PM 1/17/2002]

Tom454

That would be my "guess" too. But I think I am wrong. So I await a better answer....

This "doubting Thomas" thing is a curse.

lbell101

I believe it turns black because it is made to absorb contaminants. Chemicals are added, called dispersants, which help the oil to contain the dirt. This is done for two reasons. The first is as a carrier so that the filter can remove the majority of the harmful particles. The second is to help in the removal of contaminants when draining the oil.

Not an expert - but logical.

Rowdy Rat

Tom,

When I first started using Mobil 1 some fifteen or so years ago, the recommended change interval listed on the container was 25,000 miles (with the usual "your mileage may vary disclaimer), so obviously Mobil felt relatively confident that their product could deliver as promised. I don't know if this change interval is still listed on the container, perhaps someone else can respond to this.

I know that many of the car manufacturers these days recommend 7,500 mile oil changes (again with the disclaimer for severe use). I would gather that while manufacturing techniques have improved (and have eliminated a lot of the garbage that usually floats around in a newly cast/machined engine) a lot of the credit has to go to the improvements in motor oil technology. My limited understanding of motor oil is that the additive package is usually the first thing to be compromised by wear and contamination. It is this area along with their ability to operate at higher temperatures without breaking down is where synthetic oils have an advantage.

I don't disagree that the oil may be darker in color than when it was put into the vehicle. The assumption you're making is that because it is black, it no longer functions the same as "fresh" oil... I'm not sure that I go along with that. According to Mobil (and apparently zwede's independent test as well) there is no effect on performance.

From a practical standpoint, my S10 pickup with 115,000 miles and my former GTI with 220,000 miles seemed to live just fine with 7,500 mile oil change intervals. The other cars that I own don't see quite the same use and the oil is changed on an annual basis regardless of mileage.

I too would like to hear the whole story from an expert in the petroleum industry Tom! It might shed some light on what we're discussing here.

Regards,

zwede

Larry hit the nail on the head. The dark color doesn't mean the oil is used up, just that it is doing its job. It's trasporting "dirt" to the filter. Until the filter is used up, the "dirt" level will be at a constant level.

What determines if the oil needs to be changed is additve package breakdown or contamination by such things as antifreeze or fuel. Oil by itself does't wear out. The additive packages that make it multi viscosity, transport dirt, etc DO break down.

The "dirt" that makes the oil dark is just carbon deposits pushed past the piston rings. It is not harmful by itself. Any particles large enough to do damage will be caught in the filter.

What makes me say 7k miles is ok is that the levels of iron,aluminum etc were still low. This means the oil never broke down and stopped lubricating. The fact that the viscosity was still 10W-30 means the additive package had not broken down.

Of course the oil was dark when I drained it, but again, that by itself means nothing.

norvalwilhelm

My wife's new bonneville does it's own oil check? She came in last night and said the message came back that her oil is 88% good. Don't know what that means but it sounds ok. It also said her tires are inflated to the correct pressure. Beats me how it knows. It does have a onboard compressor for blowing up toys and tires. Love those gadgets. Hope they don't break

jimduchek

From an http://www.aeroshell.com (for shell oil in aircrafts) site -- why does my oil turn black?

When a straight mineral oil turns dark or black, it usually means that the oil is starting to oxidize and needs to be changed. Because mineral oil doesn't absorb much of the dirt and sludge in your engine, the oil stays clean and the inside of your engine gets dirty. Ashless dispersant oils, on the other hand, are designed to get dirty so that the engine will stay clean. Just how quickly the oil turns black depends on a number of factors, including the condition of the engine, the dirt load, the oil temperature, the normal mixture strength, the type of fuel, the time since service, and the frequency and duration of your flights.

Basically, the important thing to remember is to change your oil on calendar and engine time, not according to its color. Also, oil analysis can help ensure that the oil is still in good condition even though it may have turned black.

From Mobil1.com:

Why does my oil look dirty when I check the level?

When your oil is dirty, it means that your oil is doing a good job. Today's detergent-type motor oils contain additives that collect and hold dirt, contaminants and combustion by-products. The oil is designed this way to prevent these contaminants from depositing on engine surfaces where they can plug oil-pump screens and cause piston rings to stick. When the oil passes through the oil filter, the contaminants are removed.


From Mobil Delvac 1 (synthetic for diesel engines) -- will my oil change colour?

It may, depending on the engine. Over the past several years, diesel engines have been designed to minimize the generation of smoke from the engine -- with a considerable amount of this soot being handled by detergents and dispersants in the engine oil. A high-quality diesel engine oil is formulated to handle high soot levels. Delvac 1 may turn black relatively quickly as it does its job, depending on how much soot your engine produces.


At any rate. There ya go -- it appears that it's OK that it be black. I personally had always thought it was something to do with thermal cycling, but I guess it's just dirt on it's way to the filter.

Jim

Gameshow Bob

Zwede is running an MPFI system. I have a feeling that has a lot to do with the longevity of his oil. If you're running a perfect air/fuel ratio oil contamination should be minimized. I have a feeling that the 3000miles/oil change number is based on carbeurated engines and is probably a safe number for most c3's. New cars with fuel injection can probably get away with longer between oil changes. :cheers:

Tom73

Jim,
Thank you for posting that info. Will help clear up a lot of peoples thinking.

tom...

PRNDL

What a coincidink! I was about to ask a related off-topic question:

I have been amazed at how clean the oil stays in my 97 lexus es300 even after 5k miles and time to change the oil.

Meanwhile, our 92 volvo (4 cyl) seems to turn the new oil black after about 500 miles. I was going to ask the owners of new American cars if their oil stayed relatively clean looking for 5k miles?? MJ

Gameshow Bob

In my '96 Intrepid the oil stays pretty clean; even after 150k miles (engine, not oil).


[Modified by Gameshow Bob, 1:53 PM 1/17/2002]

Flareside

Mark, both my Ford truck (2001) and Maxima (2001) come out almost completely clean at 5000 miles. The Vette comes out black after 1000 :(

EDIT: Gameshow Bob may be on to something. My car has good rings with no blowby that I can detect, but it does run very rich. Black oil cause?

I guess I'll find out if Summit ever delivers my EFI system :sad:


[Modified by Flareside, 2:57 PM 1/17/2002]

Gameshow Bob

I was also looking into getting the small block version of the commander 950 system. Has anyone seen it anywere? Im sure jegs or summit would special order it for me from holley, but that'd just take even longer.