After I get a Change oil message, I start getting a Oil Life remaining message expressed in percentages.
How is this calculated? Is it based on opacity or viscosity or mileage or what?

Curious minds want to know........

 

wow 14 years on this forum......hundreds of posts on this subject. Lots of wasted time and bandwidth.,

 

Thanks for the insight....

 

No problem

 

Tables for oil life are usually calculated from tables of info like:
fuel consumption, miles, time, temperatures

 

when it says zero, change the oil

 

This might help explain it. I thought I had a more detailed explanation, but can't seem to find it at the moment.

You can always google oil life monitoring systems and see what comes up.

 

The development of the Oil-Life System began over a three decades ago by GM research engineers Shirley Schwartz and Donald Smolenski, both of the GM Research Laboratories. They discovered, through various investigations, that oil degradation, in general, followed pathways influenced by service and environmental conditions. The extremes of these conditions, are high-temperature, high-load on one end and low-temperature, low-load on the other. In between is the large operating domain representing the majority of driving conditions. The basic design of the Oil-Life System was intended to characterize extreme operating conditions and most points in between.

While the Oil-Life System does not actually monitor any single quality or physical property of the oil, it does incorporate the use of a highly sophisticated mathematical algorithmic model. This model applies the known influence of oil service temperature and revolutions to characterize the remaining life.

The influence of temperature, in particular, has a marked impact on oil life . Where a significant additive for heat was specified into the required oil The almost parabolic nature of the aging rate with temperature emphasizes the importance of this as dependent variable. On the other hand, time or running time (in the absence of mileage or engine revolution data) was not found to be a particularly good indicator of oil life, since it did not adequately distinguish between periods of extended idle and periods when engine speed was high.

The onboard calculation of oil age was simplified by using penalty factors (as opposed to equations). A penalty factor is an indication of the rate of oil aging at a given operating temperature. For any given oil, higher penalty factors are associated with faster oil-aging rates. The model uses engine revolutions as a basis for measuring duration of service.

Gathering the data to show correlation of on-board measurements of oil-change intervals to laboratory oil analysis is a slow process, requiring months or years. For example, a typical short-trip service test can last two years. During the original research program approximately 180,000 kilometers were accumulated in determining the constants for the mathematical model and another 180,000 kilometers were logged in testing vehicles equipped with the Oil-Life System.

the results of four analyses, as indicators of oil degradation, are plotted as a function of distance traveled for the three test vehicles. The four oil analysis tests are:
1. Total Acid Number (TAN)-Concentration of acid constituents in the oil from oil oxidation and combustion products.
2. Total Base Number (TBN)-Depletion of over base detergent additive.
3. Differential Scanning Calorimetry (DSC)-Approximates the remaining life of the antioxidant (residual oxidation induction time).
4. Pentane Insolubles (PIN)-Concentration of carbon soot and sludge.

The point at which the oil-change indicator signaled an oil change is also shown. All oil analyses results are plotted, including those data points regarded as "outliers", that is, points with values differing by more than approximately 20 percent from the trend lines from all data. It is interesting that DSC data followed a rapid decay curve from the outset. Also interesting is that both TAN rises and TBN falls at an apparent increased rate near the point where PIN rises (about 16,000 km). TAN increases exponentially even though not all of these changes occurred with each vehicle and there was usually some oscillation in the data, it was still possible to use these generalizations as guidelines to characterize the oil aging process. Consequently a one year change recommendation was established.

From these studies and other subsequent investigations it is clear that there are distinct benefits to drivers of vehicles equipped with the oil-life monitoring systems. For those who neglect to change their oil on a regular basis, the system provides reminders that a change is due. If they need the reminder and follow through with an oil change, they'll protect their engine from premature wear. And, drivers who thought they needed to get their oil changed every 3,000 miles (5,000 km) or so, might be able to go longer between changes. This will save them money, time, and perhaps more importantly, precious natural resources.

Just another log on the fire... our test analysis was so good we used the base line from 10,000 miles/16093 km to 15,000 miles/ 24140 km in 2000, but the one year recommended change is still required. Its just insurance for those who's toxic level may not be critical, but like the smoke alarm batteries. without an oil test sampling. Use the OLM or the one year recommendation.

Bill aka ET

 

Thanks for the detailed explanation. I just changed my oil this weekend with the OLM at 5% and it's been about a year since I last changed the oil. (~5-6000 miles --not really sure since I didn't make a note of the mileage)

I had forgotten about the one year interval, so I'm glad you reminded me of it. I'll keep that factoid in the back of my mind.

 

Factory fill, Mobil 1 oil also says one year oil change regardless of mileage.

 

As I have said many times. Use the OLM... it works...you can take it down to Zero before the change.. what I tell people is when they receive the first message change oil soon. that's when you should buy your oil and filter or get ready to make an appointment to have it changed.. We tried to make this model as user friendly as possible.. make it as maintenance trouble free as possible... also it protect the environment for wastefully using resources. The OLM cost GM a lot of money to develop and upgrade.. its not a gimmick. Many members are seeing 300K and 400K out of their LSX engine following this system, and the recommended oil spec with C5 heat sensitive additive package., Remember, use the OLM or 1 year, which ever comes first.