3000 MILE OIL CHANGE TRUTH
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By Bill Siuru, Greencar.com

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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.

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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.

 

Here is the link

http://autos.yahoo.com/articles/auto...MzMDAwLW9pbA--

 

Good articles guys, heres an older one but still relevant that I like to quote.

http://www.xs11.com/stories/croil96.htm

 

Funny, I've been saying this for years. When the owner's manual says "change at 5K" & your local lube shop says "no 3K" I'd rather believe the guys who put the car together than someone who's just trying to sell you more oil.
I follow the owner's manual: 7K with 0W-40 & that's exactly what I do.

 

It really all depends on the driving condition and what kind of driving you are doing........For me, I race a lot and am hard on the car on the street so therefore I like to change it at 4-5000k instead of the 7500k it states.

 

Seems like I recall the syn/oil labels saying good for15k miles

 

Good point. Under those conditions it makes sense!!

 

I have been doing this for a number of years now. It makes sense.
My Caravan and Jeep 5,000 K.
The XF when the FSS system tells me to.
Resetting the FSS. That's fun

 

Resetting the FSS.......I'm going to have to rethink my distaste for the cup holder & vote that resetting the FSS is the biggest pain in the butt on the Xfire!

 

The documentation that I have read has changed my thinking and I am not down with the 5000 mile idea in everything but my mower. The three thousand figure was common knowledge back back in the day.

Back then the cars needed serious work yearly like valve jobs and 500 mile break in cycles for new cars. Time have a changed..........Enjoy, Woody

 

When working as a performance engineer in the automotive industry, I have often did chemical analysis on motor oil of test vehicles every 5000 Km and even after 10000 Km of intensive testing (high engine load, high RPM...) the oil rarely got compromised.
Even the newest exotic vehicles now have service intervals up to 20000 Km.
My VW after 10k mi reccomends the oil change every 10k miles.