This post is directed specifically to those using synthetic motor oil (Mobil 1 or others) and changing oil/filter at 10,000 mile intervals as recommended.

All others please stay out of it as we don't need to start another endless/useless thread on the subject of brand, type, time, or distance for motor oil. Please don't high jack this thread with off the subject opinions and responses.


Now the question.
In your experience, is it normal for the synthetic oil in an 05 XJR to be dark brown after 6,000 miles? Brown like an old penny describes it. State of tune is excellent. Should I reconsider going for 10K? Informed opinions please.

 

I'll offer the advice of not using the colour of oil as an indicator of health. Over and out.

 

For $25 you will know (www.blackstone-labs.com).

 

Echo Mikey....if dark oil color was indicative of a problem, my diesel ExC wouldn't be "running like a (top/sewing machine/scalded cat)" at 178K mi. - but in fairness...10K mi. not recommended for it and I don't stretch it out that far. Even so, it tends to old penny very quickly after a change.

Have used Blackstone labs for the dsl a few years ago and it was a good experience. Would not hesitate to do business with them again.

 

Sage advice. Using color of oil to draw any conclusions is just as accurate as consulting a tarot card reader. In fact, a tarot card reader (depending on the reader. You can never underestimate a good psychic) might be more accurate.

Lab analysis is the modern and intelligent method. $20 at Blackstone, probably a fraction the cost of the Tarot card reader.

Oil has three responsibilities:

1. To Lubricate
2. To clean
3. To cool

If oil is turning brown it is doing #2 (pun intended), like it is supposed to do. Now the mystery, when does it stop cleaning? A lab analysis will tell you.

 

Thank you gentlemen all.

It looks like Blackstone is the only sure way to go. I'll give em a shot.

Hay Steve11. Nice to see you back in the game of late. It seemed like you were scarce for awhile. I was concerned you had flamed out.

 

Not back, just stopping in for a very short visit. Some topics are just too enticing and I am weak. I find it far less frustrating and far more entertaining to just lurk this site or stick to off topic.

 

Yep ... even if the oil goes a light creamy coffee color you shouldn't listen to the old timer telling you there is coolant mixed in there ... send it to blackstones.

 

Technically OIL has 6 Functions in reciprocating engines.
1 Lubrication
2 Cooling
3 Sealing the piston rings
4 Cleaning and holding deposits in suspension
5 Corrosion Prevention
6 Cushions Parts from impact loads

If you ever have taken the FAA A&P written exam, you will need to know this for one of the questions.

bob gauff

 

Great explanation by motorcarman , keep us updated on the oil test

 

I use synthetic and change it around 6000 miles. It usually is getting darker about then. If it has suddenly gotten darker, it is possible that it has dislodged or dissolved some old sludge. I had this happen in a used Jeep (50K miles) I bought and changed to synthetic recently. After about 5000 miles on the synthetic, it suddenly had a lot of valve racket on start up. It was the synthetic oil dissolving the sludge in the hydraulic lifters. After a few days of this, the oil suddenly got dark and the racket stopped, all dissolved! It was nerve wracking but I lucked out.

 

True enough; however, no one is looking to get certified by the FAA from the information provided in this thread, nor is it germane to the topic. I tried to lend a more simplistic layperson's level reply that would be easy to remember and helpful to this level audience. I'll let you pick it up from here...Frustrating!

 

You gentleman will recall that my intent was to use Mobil 1 synthetic oil in my 65,000 mile 05 XJR and run it for 10,000 miles between oil and filter changes. Not wanting to take any chances with my perfectly running machine and on the advice of certain Forum members, I sent a sample of the oil off to Blackstone Labs for analysis after 6,000 miles.

The car uses 1 qt. of oil per 5,000 miles.

To make a long story short, Blackstone recommended I not run the oil past 7,000 miles as the additive package and filter would not be so good after that.

Conclusion: For me and this car I will run high quality regular oil and change oil and filter at 5,000 mile intervals.

 

I have little or no faith in the analysis of a single sample. A credible program would sample the oil every 500 miles or so and look for trends. What in particular was 'failing' in your oil for them to make that statement?

Why not send them a another sample at 7K miles and ask specifically what has changed.

 

Mikey,

Blackstone's main concern was that the additive package was getting too thin to risk going past 7,000 miles with it. Keep in mind that central FL Summer heat is, while not hostile, quite demanding on oil.


I don't think multiple testing is going to tell me any more than I need to know re additive package life. Mind you, there was a page full of data returned to me but most of it was irrelevant to my main concern, well within norms or above my pay grade.

 

Would you be willing to show the results?

 

There is nothing that is beyond comprehension in the list given by motorcarman. If it stretches the audience a bit, maybe that's a good thing. That's how people add to their knowledge base.

 

Seems sensible. The combined cost of quart lost by 5k and the cost of continuued testing would pay for a good chunk of the oil change.

 

Yes and no. This is the classic case of 'beware the questions you ask for you may not like the answer'. Most owners keep the hood shut and change the oil at whatever interval they like, ostensibly many at the OEM recommended interval. There's no known deterioration or failure pattern on this engine to state that any particular interval is good bad or indifferent.

The OP essentially opened Pandora's box by testing his oil. He got an answer that suggests that the all hailed synthetic oil is NOT suitable for extended service periods, it's not even good enough to last the OEM interval. At a 5K interval, why use synthetics at all? Should us dino users half that again and change at 2.5K 'just in case'?

As stated earlier, I have little faith in the results of a single sample. In an greatly exaggerated sense, this would be similar to a doctor recommending a massive lifestyle change or heart surgery based on just one blood pressure reading.

 

Mobil 1 changed their formula away from true synthetic several years ago. Mobil1 is no longer the oil it once was. This must be part of any consideration or discussion regarding Mobil 1. In that light, I believe that Mobil 1 just isn't worth its salt, and that one should never rely on it to provide superior protection much longer than conventional oil.

My conclusion regarding motor oil years ago: use conventional and change at a more frequent interval, or go with Royal Purple or Amsoil, and get ready for a completely different paradigm, a paradigm I certainly can't afford to play in.