I see that new cars and trucks have a gauge that give you the life of the engine oil as a percentage. Is this gauge based off of mileage or is it an actual measurement of the oil quality?

 

Can't speak for all vehicles, but I have a 2003 Monte Carlo with this feature, although it doesn't give percentage, only when it's past expected life. From what I've read on it, it uses engine RPM and temperature to calculate oil life. Depending on how you drive it, theoretically, you could go 1500 miles or 7000. I'm not willing to trust it as I'm pretty sure you'll find it hard to convince someone to cover the motor under warranty because the car didn't tell you it was time to change the oil.

 

The oil life indicator is based on an SAE award winning algorithm that GM developed in the mid-90's. The ECM uses fuel injector duty cycle, engine temperature, and load to determine the life cycle of conventional motor oil. I once attended a seminar in early 2002 on how it worked. I've trusted it for the life of my 2001 Chevy Venture minivan, never changing oil until the "change oil" light comes on. Now, with 108,000 miles on it, I still have no problems in the engine whatsoever.

The trouble with oil is that if you don't get it warmed up enough, it collects solubale water in the oil, and this encourages the acidity of the oil to increase. The Acidity rapidly neutralizes the oil additive package, leaving the oil unable to continue neutralizing the acids that will inevitably attack the bearing surfaces of the engine. That is why cars that take only short trips will require shorter oil change intervals than cars which take only long trips. It takes about 2 miles to get an engine warmed up enough to drive out the condensation in the engine; Especially during the winter.

 

what about putting synthetic in it?

 

Well, synthetic oil is a whole story to itself, but be it dino or synthetic oil, they should be changed at the same intervals.
Synthetic oil doesnt get less dirty then regular oil. It just doesnt break down as fast or aerate like regular oil does. A TRUE Group IV based synthetic oil can go longer between oil change intervals, but they cost much more.
Follow the OLM, and you should be fine no matter what oil you put in. OLM's tend to put it at 6-7k miles between oil changes anyway.

 

So with this feature, do you have to have an oil change done at specific places to have the computer "reset"? I may just be ignorant, but if I was to change my own oil, I'd hate to ride with a "change oil" indicator on until I was able to take it somewhere to be cleared.

This is just the first I've heard of this and was curious.

 

You manually reset it. If I remember correctly, they said to change it with a few hundred miles from when the light came on. Keep in mind, mine's an 03 and they probably have changed somewhat, but mine resets through the factory radio menu. Of course, that meant I had to move the factory radio to the truck when I replaced it so I could continue to reset it.

 

It's not hard to reset the oil change monitor. You usually can reset it by lighting up the oil change percentage on the driver console, then pressing and holding the odometer reset pin on the gage cluster. Sometimes you need to have the key in the ignition, and the engine accessory position enabled, but not have the engine running. Your owners manual will describe how to reset it.

 

On my CTS you just hold down the reset button for 5 seconds, and bam, back to 100% and you are ready to roll!

 

Heck, I went 10,000 miles until my last oil change and the oil life meter was still at 30%.

 

well i have it in my hummer and i have gone over my recommended miles before changing. the light has never come on. i think it is based on the condition of the oil.

 

It's not based on the condition of the oil. It is based on an algorithm in the ECM which calculates oil life based on the duty cycle of the engine. If you burn a lot of fuel per mile, putting around town or hauling heavy loads, or if you experience a lot of engine warm-ups and cool-downs, it will reduce your oil life. Those things are measured by the ECM, which then calculates the life expectancy of the oil.

If you are doing a bunch of 5-mile commutes and very few short trips, your oil life could be very long indeed. That's the beauty of this system.

 

FACT! Just had to change the oil on Number 3. The "change oil soon" came on at 5% oil life remaining. This was with 10,500 miles on the clock which had a lot of highway with the trip to California.

 

I read somewhere that the car comes with synthetic, also is it required that you change the oil at 500 miles for the initial break in?