Does anyone know how the determination is made that it is time to change the oil? Is it based on miles, RPM, viscosity, or a combination of factors. I use synthetic oil and it has been about 6K miles since last change. I think that I should be able to go 7500 between changes using synthetic, less if I'm towing frequently. What do others think. If the determination is based on viscosity then I would probably follow the recommendation. If it is based on miles or RPM then I would be inclined to wait since Chevrolet probably assumes the use of conventional oil in making the determination.

 

I assume it's telling you it's time to change?

 

Yes, I am getting that message now, but as I said, since I use synthetic oil and haven't been towing, it may be that the criteria for the indicator don't apply.

 

As I as I understand it, the oil life monitor system (OLMS) algorithm is based on everything that wears out the oil such as speed, temperature, etc.

I believe it is based upon using conventional oil. I use Mobil 1 and change the oil when it says its at 0%.

 

Thanks, it would be interesting to know just how the OLMS system does its calculation. It might be proprietary but if not it would be enlightening to find out. A friend talked to a service rep at a GM dealer and was told it was just cumulative RPMs

 

Using the OLMS terminology I was able to Google it and found several useful articles. This one was quite good: GM's Oil-Life System Improves Timing of Oil Change. Basically it says that the change interval is determined by temperature and RPM.

 

syn oil is so inexpensive these days why push it to 7500 miles. no algorithm measures oil dilution, particulate matter in suspension or when the additives or modifiers wear out. Even the engineers to designed the system have changed its originals parameters to trigger sooner...you know more than them?

 

Synthetic oil every 5000 miles. Cheap insurance. Why mess around? Only time I deviate from that is if the oil change message comes on before the 5k.