Has anyone sent oil in to be tested? I know oil technology has improved a lot in 18 years and I'm thinking I may change my oil change interval if the life of my oil is better than expected. I use Mobile 1 full synthetic and usually change every 5,000 miles. If oil quality is better than 30% after 5,000 miles I may extend.

I also read that some labs will also report of other issues that may be creeping up like head gasket, wear and/or PCV issues.

http://www.edmunds.com/car-care/when-should-you-change-your-oil.html?articleid=164688

 

Yeah I've been thinking about it too; suspect the 850 may have weapy injectors. Anyone know of a simple test for fuel in the oil, I'd be interested. The smell test isn't too accurate..

here's a good article on the topic:
Engine Oil Analysis - Bob is the Oil Guy

 

I use Blackstone Labs. But the cost of the oil analysis is about the same as the cost of five quarts of oil. So continuous oil analysis is not really cost-effective on passenger vehicles. The way to approach it is to run a longer OCI, do one oil analysis and based on that make a decision on how long to run your oil in the future.

I can tell you I would (and have) run Mobil 1 up to 10,000 miles. I use Mobil 1 EP in my Toyota Sequoia and run it at least 15,000 miles. I have attached an oil analysis after running this oil almost 21,000 miles.

 

I understood some of it but not all. I was expecting to see some kind of comment or statement indicating that there was some percentage of life left on the oil.

From what I could tell, you ran the oil just shy of 21,000 miles and added a little over 2 quarts during that time. They said all looks well and they suggested that you run 22,000 miles before the next change???

I don't have a problem paying $25 for the service, especially if I find out I can extend my change service or cut off some creeping issue I have. I'm changing oil 6 times per year now, full synthetic at $37 per change. If I can cut that down to 3 or 4 I'll make that back in a few months.

 

That would be the TBN (Total Base Number). There are really only two things that cause the oil to no longer be useable - viscosity out of range and acid-neutralizing additives depleted. The TBN measures the acid-neutralizing ability of the oil. The third factor that influences oil serviceability is the insolubles. If all three factors are acceptable then the oil is serviceable indefinitely. This is how the big rigs can run their oil 100,000 miles or more. The Mobil 1 EP I use is probably good for 30,000 miles or more in my Sequoia but I see no need to push it that far. My approach is pretty much to change my oil once a year.

Yup, but Blackstone always suggests you run your oil a little longer if the analysis is good.

The TBN analysis is an additional charge, so about $30 total, IIRC.

 

What is IIRC

 

So what are you looking for in the TBN? Yours say 3.3, is that good? Does fresh oil start out as a 5.0?

 

From the link in post #2 of this thread:

The TBN (Total Base Number) is a lubricant’s reserve alkalinity measured in milligrams of potassium hydroxide, or calcium sulfonate per gram of oil. In more simple terms it is the amount of active additives remaining. This number is important because combustion byproducts tend to form acidic compounds and the TBN is the acid-neutralizing capacity of the lubricant. The TBN does not decrease linearly with the time it has been in use. Example: it could start out at a TBN of 10, drop to 5 after only 1,000 miles of use, and then stabilize around 3 for a majority of the remaining service life. A TBN of <1.0 is generally considered to indicate near depletion of additives, and is a safe point to change your oil. Once the additives are depleted then the infamous sludge that the crazy Scot from the Castrol commercials has been warning us about can begin to form. A virgin sample of the identical oil that I used here (Pennzoil Ultra 5w30) begins with a TBN of 11.7.