A few months ago I wrote and recorded a car care tip that aired on XM Satellite Radio. To the best of my recollection, the tip was an answer to a question addressed to me from a listener in California. She wanted to know why her vehicle's 'oil light' was telling her to change the oil in her new Chevy Trailblazer (having changed it just 1500 miles previously). I advised her to ignore the light because that system (GM's Oil Life System) only counted engine RPMs since the last oil change, and therefore was reading inaccurately. I advised her to follow the 3,000 miles (severe service) schedule and have the vehicle checked under warranty, after which all would be fine. That tip was heard in Milford, MI and prompted a letter from an engineer in GM's PowerTrain Division, exhorting me to conduct a bit more research about GM's Oil Life System. He informed me that I was correct in my statement that the system monitored engine speed, but that there was much more to the system than I realized.

Curiosity got the best of me, and I accepted his invitation to discuss the matter. I contacted Tom Read of GM's PR Department for GM's PowerTrain Division. That phone call led to a conference call with four GM engineers, two from GM Parts & Service Division and two from GM's PowerTrain Division. Their goal? To convince me that GM's Oil Life System (GMOLS) has changed things drastically regarding conventional oil change philosophy. I took the challenge rather aggressively ... as they did.

I began my 'attack' by pointing out that the GMOLS only monitored engine RPM since the last oil change (providing the system had been reset when the oil change was done). I asserted that there was much more to take into consideration when determining oil life and quality. Conditions such as engine temperature, load, and ambient temperature had to be taken into consideration. I went on to state that these factors could adversely effect the life of the oil. For instance, load from towing could raise engine temperatures to the level that the oil would break down. Or ambient temperature could effect the performance system by causing a richer fuel to be delivered, contaminating the crankcase and resulting in oil breakdown. The engineers politely agreed, and then they proceeded to enlighten me.

They pointed out that I repeatedly used the term 'viscosity breakdown,' and that I must understand that this term has a two-fold meaning. Before the breakdown of the oil occurs, it actually thickens! To draw an analogy ... oil is much like the value of your new car. The moment you drive it off the lot, it begins losing value. As soon as fresh oil begins circulating through a vehicle's system, it loses value. How, you ask? Chemical packages start breaking down immediately when introduced to the harsh environment of the engine. So, hypothetically, you could find yourself six weeks after an oil change and suddenly the oil becomes thicker, resulting in hampered flow (viscosity or flow-ability breakdown) within the engine. This results in increased friction (heat) and thus shorter engine life (and the condition is multiplied dramatically when outside temperatures drop below 35 degrees). Sometime after this occurs, oil breakdown takes place, meaning the oil loses its ability to lubricate. This breakdown differs with each vehicle because engine demands vary, depending on driving habits and vehicle use. The key to maintaining oil stability is to keep the oil temperature at 200 degrees consistently. Oil life is maximized under these conditions. Highway driving exemplifies this type of operating condition.

While consulting with the GM engineers, I discovered that GM takes into consideration more than just engine RPMs with the GMOLS. Below is a brief history of the system and how GMOLS works (taken from GM's website).

The GMOLS Offers Significant Benefits

"First introduced in 1988, the GMOLS is a computer-based algorithm that determines when to change oil and filter based on engine operating conditions (this is the key to accuracy). The system enables owners to maximize the performance of their vehicle engine oil by sensing engine speed (not RPMs, but actual engine revolutions) and temperature. There is no actual oil condition sensor. Rather, the computer continuously monitors engine-operating conditions to determine when to change oil." "With the GMOLS, consumers have an accurate and reliable way to monitor engine oil life. When the system is activated, consumers can go to their nearest GM Goodwrench dealer and a technician will change the oil and filter, properly dispose of the old oil, then reset the vehicle's oil life system. Overall operating costs for the customer will be lower, because they only have to change the oil when needed, and they can be reassured that their engine is always running with good oil, improving the long term performance and reliability of their GM vehicle."

"Use of the GMOLS will often double or even triple the oil change interval for a typical vehicle when compared to the 3,000-mile oil change. "

"The GMOLS will automatically adjust the oil change interval based on engine characteristics, driving habits and the climate in which the vehicle is operated. For instance, mild highway driving in a warm climate will maximize the interval between oil changes. Depending on the vehicle, this could be in excess of 7,000 miles and as high as 12,000 miles (in some models). On the other hand, short trip driving in a cold climate may limit the oil change to 3,000 miles or less. In general, most people that drive a combination of city and highway find that the GMOLS will indicate an oil change every 5,000 to 6,000 miles. GM data shows the OLS extends oil change intervals without risks to the engine."

(And for the Militant Tree Huggers and Energy Conservationists)

The GMOLS can offer significant benefits to the environment by reducing unnecessary use and disposal of oil. GM has built more than 20 million vehicles to date with the GMOLS. In the next five years, if the GMOLS is used as intended - oil changes performed only when necessary - millions of gallons of oil could be saved."

(Oil conservation and a cleaner environment?! Is everybody happy?!)

GM has so much faith in the OLF system (based on countless individual tests performed by engineers) that they have issued a new "Simplified maintenance Schedule." It goes like this:

"The new GM simplified maintenance schedules are performed in two phases. The first phase, 'Maintenance I,' includes basic services such as an oil and filter change, lubrication of chassis components, tire rotation and inspection of the brake system and fluids. The second phase, 'Maintenance II,' includes all services included in Maintenance , as well as inspections on the steering system, wiper blades, restraint systems and lubrication of body components. "Customers don't have to worry about deciding when the best time is to change their engine oil because our Oil Life System technology adapts to their driving conditions and habits, and determines the right interval," said Peter Lord, executive director, GM Service Operations. "Since the new maintenance schedule is based on oil change intervals determined by this technology, customers can save time and cost."

My conference call lasted one hour and fifteen minutes. The engineers were passionate in their arguments. These experts are committed to getting the message out there with respect to oil changes. The information they shared was compelling, to say the least. The conversion was complete ... I am a believer. Everything they stated was consistent with my knowledge of the internal combustion engine. GM has invested millions of dollars in research and development and exposed themselves to potential warranty claims ... they've put it all on the line with this innovative approach to timely oil changes. That says a lot. A wise person is one that admits they can always learn something, and I learned something from GM that day ...

'Til next time ... Keep Rollin'