Reason that Mobil 1 darkens is...

[JAG]

Well it's tough to say because it is temperature AND time dependent. One extreme example is that I was able to turn most synthetics very black in 30-60 seconds if I had them at over 600F degrees.
Mobil 1 5w30 and 10w30 did darken noticeably when at 300F degrees for several hours, while the Castrol Syntecs I tested barely changed color. In an engine, the oil may never get over 220F degrees, but it's in use for MANY MANY hours, so it's enough to darken the oil just from heat.

To determine if an oil needs an oil cooler would be much better done by at best measuring the oil temp or at worst using a pyrometer on the oil pan. There are so many variables involved in the color change of used motor oil that going by that is shakey ground to stand on. Some conclusions can be made however. I know that for example GC's color is less affected by heat than Mobil 1 5w30, so if one engine is making GC very dark compared to another engine using M1, the engine using GC is either running longer intervals, getting more blowby (carbon) into the oil, or it's running HOT AS HECK (>300F likely). GC takes such high temps to change color that no healthy engine will get the oil hot enough to change it just from heat.

 

[Volvohead]

Why don't you take a pan of M1 and a pan of your favorite conventional (or synthetic), and heat them both over a torch, but past their thermal breakdown points, and then see what happens. Yeah, we did that sort of thing years ago too.

The M1 might darken up, but the conventional will break down and tar up first, usually much sooner. The same can be said for some of the older Syntec formulae.

I don't care about any oil changing color once in service. It indicates absolutely nothing concerning the essential properties of the lubricant. It certainly isn't probative to thermal oxidation and breakdown. And other than when I put it in and drain it out, I don't stare at the color all that much. It just isn't that much of an automotive fashion accessory. Maybe if I had a leaker, I'd feel differently and try to find an oil that better complimented my block paint.

I'm curious to know how you figured it was the add packs changing color as opposed to the base stocks. And just what colors are moly, zinc and calcium anyway? Are those clear deodorants better, too?

Speaking of smell, you could also go with the oil smell protocol. My one mechanic friend says that the engines running M1 just smell better when he tears them down compared to other oils. Is it the add packs or the base oils that get so stinky? Perhaps the extra stink is a sign of added oxidation with the others.

I think that only the taste test will be dispositive on the issue.

 

[Digital2k2]

Just wondering did you test pennzoil platinum?

 

[JAG]

No I didn't test Pennzoil Platinum but did test the older Pennzoil 10w30 Synthetic (API SL) about 2 years ago. I think it had the name "Penzane" or "Pentane" in it's ad literature. I don't want to discuss the results because the Platinum could be much better than the old Pennzoil synthetic.

 

[speedtc]

Cause it's an inferior 100% full syn?

 

[Dr. T]

Yeah, that't the irony of this post. M-1 is the only 'true 100% PAO blah, blah, blah' synth. and it gets black faster than Syntec's 'non-synth group III close-to-dino oil'.

Wonder how it does for deep-frying?

But seriously, doesn't this indicate heat-resistance somehow? eg. if an oil can't stand the heat...well, you know the rest...

 

[speedtc]

I couldn't resist!

 

[Oldmoparguy1]

I sure would like to know what RTS 5W40 does.
At ~3500miles, the RTS in my turbo Caravan is a medium dark amber, about the same as the M1 in my 2000 GC at ~5400miles.

 

[JAG]

Alright fellas, apparently my attempt at giving only a small portion of my OCD-inspired oil testing has opened pandora's box and spread from the color change topic to oxidative stability and the other things that really matter. It sounds like there is a desire for more data. I do not have enough spare time on my hands to present all of the results from several years of testing, but you may look at the list of oils tested below and ask any questions you have.

The purpose of the testing was to evaluate how the oils reacted to high temperatures. Whatever could be observed was and was recorded but the main focus was on (1) viscosity change resulting from the opposing effects of oxidation and break-up of viscosity index improvers, (2) flash point, (3) deposit formation, (4) volatility. The color and odor was noted but not used in any judging except when the odor indicated oxidation had occured. I did these on my own time out of scientific curiosity. I was not being paid by anyone.

Mobil 1 5w30 EP (SL)
Mobil 1 10w30 (SL)
Mobil 1 0W-40 (SL)
Castrol Syntec 5W-40 (SL)
Castrol Syntec 10W-40 (SM)
Gold German Castrol (SL)
Valvoline Synpower 10w30 (SL)
Valvoline Synpower 5W-40 (SL)
Amsoil 5W-40 (SL)
Pennzoil Synthetic 10w30 (SL)
SAE 30HD weight Pennzoil dino oil (SJ)
Redline 5w30 (bought in 2002/2003 so ?)

 

[GMorg]

If you guys like this topic, download the following pdf. "Composition and Oxidation Stability of SAE 5w-40 Engine Oils" Cerny, et.al.

www.oetg.at/website/wtc2001cd/html/M-21-P58-614-CERNY.pdf

The paper is a comparison of various oils and their stability. Notice that "fully-synthetic" oils are present in both the best and worst performing oils.

Also, keep in mind that heavily hydrocracked oils can be very heat stable and may even outperform PAOs in this parameter. Knocking on Syntech because they profit on less expensive bases stocks does not mean that they make an inferior product. They just get rich quicker...

 

[Matt89]

Maybe the Mobil1 just did a better job of 'cleaning' the container that you heated it in

 

[Dominic]

Maybe it would season my iron skillets better?

 

[michaelc80]

quote:

---

The purpose of the testing was to evaluate how the oils reacted to high temperatures.

---

How did you set up and control the tests? Over a stove with the possibility of temperature variations? Controls on quantity of each item being tested?

I think the "skillet test" has a minimal amount of merit (if that was your method). It does a very poor job of simulating the environment inside an engine. After all, inside the engine there are 4-8 quarts of oil total constantly under movement. In a skillet on the stove it's a different environment and the heat would "fry" any oil much quicker.

I remember a commercial like that a few years ago. Didn't strike me as much of a test then either.

 

[moribundman]

I question whether or not dyes are temperature stable. Since all or most oils are dyed more or less, the amount and type of dye added may well affect how dark an oil turns. Castrol 5W-50 stayed very light in my engine, even over 10k miles.

 

[buster]

Probably a chemical reaction from what Tooslick said awhile back. Color is meaningless. What about those BMWs that were sludged up? Probably bc Castrol's Syntec wasn't up to the task.

 

[IndyFan]

What good is that data to us without identifying the oils?

 

[92saturnsl2]

I can definately relate to the information posted.. Awhile ago I changed the oil in my '01 Jetta VR6, which at the time had Mobil1 5w30 at 5k miles, and it was very dark brown, almost black.

Next change GC was thrown in, and after 2k the oil still looks light amber, whereas the Mobil1 turned darker much quicker.

I've always used Mobil1 and will continue to do so (may run GC in the winter), but this is definately an odd property between the two oils.

 

[Turk]

Anyone remember ARCO Graphite...???

From the mid-late '70's. "Next generation of oil". Ha!

How long did ARCO Graphite last and what made it go away...???

 

[tamu_man]

I've never had Mobil 1 get that all that dark. I had a batch of Redline get super dark, but I personally have never had M1 turn that quickly.

 

[Turk]

Oh yea - the ARCO Graphite was BLACK !

Put it in a leaky GTO and the engine was BLACK! Yuk!!