In-car Oil Quality

In my 2003 Olds (and probably other GM products as well) over time the dash display will tell you of “oil degredation” and that it’s time to chage the oil. What is being measured by the “oil sensor”? The signal does not seem to be odometer-driven since natural lubricants do appear to have a shorter live-span than the synthetic products that I have historically used in this motor. What can the sensor sense?!!

There is no sensor for the oil condition. Instead an algorithym program is used in the computer to determine when the oil should be changed. This program measures such things as mileage, RPM’s, vehicle speed, ambient temperatures, among other inputs to determine when it’s time to change the oil and filter.


The sensor does not sense anything directly in the oil! It is a computer algorithm that measures rpm, starts and stops, coolant temperature, ambient temperature, and simulates an operating mode that determines approximately how much life there is left in typical non-synthetic oil.

In other words, the cheapest or the most expensive oil will not make any difference to the operation of the program. It will distinguish between severe and easy operation, or in between,depending on the driving profile.

It is better than nothing, but you are wasting money on expensive oil since the senser treats all oils the same, and the signal will not necessarily reflect the exact ACTUAL condition of the oil.

Expensive diesel trucks have their oil chemically analyzed on a regular basis to determine possible problems and to find the proper drain interval.

My advice is, ignore the signal, but compare it with your actual change interval as determnined from experience. If the car is under warranty, follow the signal. You won’t be too far off from the real figure.

It’s environmental only. In other words, there is a computer that looks at everything except the oil itself. You’d likely get the same dash display even if you started with used oil. The display is of use mainly to the casual owner who doesn’t keep track of these things himself.

This is an actual oil sensor (not yet available in vehicles):

“you are wasting money on expensive oil since the senser treats all oils the same”

Docnick is correct, but I will add one thing. The car assumes you are using an oil equal to or better than the oil specified in the owner’s manual. So if synthetic is specified and you use regular oil, it is likely to tell the the oil is OK when in fact it is no longer doing the job.

Personally, I would ignore the indicator, use the best oil available and use a real oil analysis to determine a conservative oil change interval.

That would be correct, but I don’t think any 2003 Olds has synthetic oil specified. Only the Corvette, to my knowledge, is the only GM car that calls for synthetic. oil. A friend of mine at EXXON/Mobil some years back demonstrated the increase in speed possible with 0W30 synthetic (Mobil 1), and the Corvette team was so impressed that now all Corvettes come with it. Besides, it helps the CAFE standard.

Ten years ago GM did an elaborate test with measuring oil acidity by way of the oil’s electrical conductivity in one of their cars. Two engineers published a paper in the SAE Journal. They found good correlation, like the BMW sensor, but it was too expensive, in GM’s opinion, to offer on regular cars.

The Germans have a strong incentive to stretch out oil interval (government mandate) and protect the engines as well. All German cars now have much longer intervals than others, and in my opinion, too long. This sensor will do much to protect the engine from undue wear.

“The Germans have a strong incentive to stretch out oil interval (government mandate) and protect the engines as well. All German cars now have much longer intervals than others, and in my opinion, too long.”

I agree, I believe the new ones have a 20,000 km interval.

In my other cars, I use natural oil and change it and the filter every 5000. The Olds with 55,000 had an intake gasket replaced by GM. Speaking with the mechanic, he said that the engine looked like it only had around 15,000 on it rather than the 55K using Mobile One synthetic and going 10 K between changes. With “normal” driving, will the use of synthetic oil and changes at 10K intervals give an engine a longer life span on average than conventional oil, and changes at 5K intervals? Which of my engines will last longer (assuming an unexpected component failure )?

Mobil one is the best thing since electric, I use it it the wifes car,04 element,and 11k oil changes,still looks great inside,i use it my other vehicles also, excellent product, just do not use it in street bikes with a wet clutch,slips like a pig,yes found that out myself.and run any new vehicle the first 3k with the fact oil,as to seat the rings and mate the new surfaces properly.I know bmw,benz use it right from fact,but they run the engines in before hand.

Part of the credit for your engine’s condition goes to you!I have driven standard cars toover 200,000 miles on regular good quality oil by changing every 3000 miles, and kept the engine in virtually new condition.

Drving style and proper armup is half the battle. Good oil helps, of course.

The computer has to be reset after each oil change, so it can start the cycle all over.

I use synthetics with a 5000 mile change interval (due to diesel soot loading), my daily driver currently has 430K miles. IMO, the type of oil is less important than actually performing rigorous maintenance (including oil changes) and correcting any small problems before they can cause damage.

yep 200k on two veh,96k on the other,and 156k on the last.all at 11k changes. no diesels though.

Old diesels need more frequent changes because the soot builds up in the oil long before the oil is actually exhausted. I could use conventional oil with 5000 mile changes, but I like the wider viscosity range of the synthetic, especially for winter starting.