The 3,000 Mile Oil Change Myth
 

The 3,000 Mile Oil Change Myth
By Bill Siuru, provided by: Greencar.com

According to a recent study by the California Integrated Waste Management Board, 73 percent of California drivers change their oil more frequently than required. This same scenario no doubt repeats itself across the country. Besides wasting money, this translates into unnecessary consumption of $100-a-barrel oil, much of it imported.

Using 2005 data, the Board estimates that Californians alone generate about 153.5 million gallons of waste oil annually, of which only about 60 percent is recycled. Used motor oil poses the greatest environmental risk of all automotive fluids because it is insoluble, persistent, and contains heavy metal and toxic chemicals. One gallon of used oil can foul the taste of one million gallons of water.

It’s been a misconception for years that engine oil should be changed every 3000 miles, even though most auto manufacturers now recommend oil changes at 5,000, 7,000, or even 10,000 mile intervals under normal driving conditions.

Greatly improved oils, including synthetic oils, coupled with better engines mean longer spans between oil changes without harming an engine. The 3000 mile interval is a carryover from days when engines used single-grade, non-detergent oils.

For several years, automakers like General Motors, BMW, and Mercedes-Benz have installed computerized systems that alert drivers via an instrument panel light when it’s time to change oil. As an example, the General Motor Oil Life System (GMOLS) analyzes the engine temperature, rpms, vehicle speeds, and other driving conditions to calculate the rate of engine oil degradation. Then, software calculates when the oil needs to be changed. Other systems work similarly.

Because of the many external conditions and parameters that have to be taken into account, calculating the precise maximum service interval using mathematical models alone is difficult. Now, Daimler AG has developed a more direct and precise way to monitor oil quality directly on board a vehicle.

Daimler uses a special sensor integrated into the oil circuit to monitor engine oil directly. Oil doesn’t wear out, but rather dirt and impurities cause oil to lose its ability to lubricate properly, dictating the need for a change. Daimler uses the oil’s “permittivity,” that is, the ability to polarize in response to the electric field. If the engine oil is contaminated by water or soot particles, it polarizes to a greater extent and its permittivity increases.

To evaluate the quality of the oil, permittivity is measured by applying an AC potential between the interior and exterior pipes of an oil-filled sensor to determine how well the oil transmits the applied electric field.

Because not all impurities can be measured with sufficient precision via the electric field method, Daimler also measures the oil’s viscosity to detect any fuel that may have seeped into the oil. Daimler researchers measure viscosity while the vehicle is in motion by observing the oil's side-to-side motion in the oil sump. The slower the oil moves, the higher its viscosity. This movement is registered by a sensor and the viscosity is calculated on this basis.

A single sensor, along with the information already monitored by on-board computers, is sufficient to determine the various parameters of the engine oil. Daimler will likely use the technology first on its commercial vehicles. Here, large oil reservoirs mean larger quantities of oil can be saved. Plus, a predicted 25 percent increase between service intervals and reduced downtime will be of interest to fleets, and thus justify the added cost of installation.

Before this thread explodes:

1. BITOG is the generally accepted authority on what really works

2. Seriously, who ever has a problem that could have been prevented by more frequent / better oil? Most cars go to the junkyard with any of a million other problems, never anything that can be attributed to oil habits, even among those who follow the manufacturer's recommended schedule instead of using $10/quart oil every 3000 miles.

One data point does not a trend make, but my truck has 170,000 miles on it and runs great -- and I've been pretty awful with oil changes. I've had a few different mechanics, each of whom probably uses a different brand; never used synthetic or special high-mileage formulations. I've usually changed it when the idiot light goes on, which generally has been 6,000 to 7,000 miles. If I said all that without telling you how many miles I have, a bunch of people would post that my engine will seize before 100,000 miles. I don't get any smoke, I've got all the power to tow my 6,000 pound camper, etc...

I listen to my car. I'll let it tell me when to change the oil.:thumbsup:
60-something% life still? And I'm already over 5000 miles on the stuff.

The Oil Life Monitor system from GM works pretty well...I didn't know that Diamler Chrysler was building one that was that superior...I love technology.

Hmm funny you should bring this thread up , I just changed my oil a few weeks ago and filled it with 4 1/2 quarts of 5w30 Royal Purple and now recently when i start the car the change oil light comes on. And I know I haven't driven 5k since the change. The light goes out after about 10 minutes. Could the sensor be messed up?

Did you reset the counter? It doesn't measure viscosity and conductivity like the Chrysler system described by the OP. It just calculates how badly the oil should be aging based on load / temperature / miles / etc, and must be reset when you change the oil.

Edit: That's assuming you're talking about your 2001 Camaro.

5k is the longest i'll go between changes.

I've been changing oil every 5K for 12 years now....

But, I don't do the kind of driving that breaks down oil too quickly either.

Besides the cool computers tellin you when to change the oil......
try checking the oil on occasion, say around 2/3000 miles and then every 1000 miles or so after that. Try comparing the consistency/ cleanliness of the oil in your engine, to the oil you would put in it..... if the oil in the motor looks clean etc... wait to change the oil. If it looks black or dark brown, change it and start checking a lot sooner. :thumbsup:

Dude my Trailblazer had me all sorts of weirded out, I thought it was broken because it was taking forever to tick down to below 15%! I got it changed today because we're about to drive to Florida and didn't want it ticking down on the road trip, so I changed it at 22% but its' the first oil changed we've done on it since buying it in NOVEMBER!

I change oil when its recomended, I trust that the engineers who designed the engine know better than I do about when its time to change the oil.

yeah im talking about my 2001and yeah i reset the counter.

who knew....

I always hit the autozone soon as the light comes on

When I had my Cobalt, I obeyed the sensor every time. It usually went over 7k miles. If more people were aware of this, we could lower oil costs.