Does anyone know if the change oil light is just triggered by a timer or is it triggered by something else? Also, if it's just a timer, is there a way to reset it. I use synthetic oil and don't want to change it every 3,000 miles when the light comes on.

 

I'm pretty sure its triggered by the odometer and it hitting 3k every time.

im not sure if you can reset it. im running synthetic as well and would be interested in this.

 

You can easily reset it. Turn your ignition to on (don't start engine). Press the gas pedal down slowly 3 times. Turn the ignition back off.

The full instructions are in the manual somewhere.

 

The reminder is not set strictly by miles. It also takes into consideration start cycles, lenght of trips, driving style. The manual describes it as "duty cycle based". It does not, however, monitor oil condition, as some vehicles do.

 

I'm pretty sure duty cycle means the number of times the pistons fire.

You could hypothetically start your jeep every morning and just leave it running in the driveway all day every day... The oil light would eventually come on because the engine has cycled "x" number of times, even though you haven't put any miles on it.

Edit: The manual says an oil change is recommended every 6k miles, not 3k... I personally won't let it go that long, but I live in Maine.

 

Mine has been triggered at near 3k miles but not quite. And then again at 5500. Since I use synthetic, I don't want to change it already (it's only been 2500K since the last). You're right though, it doest say every 6K in the manual.

 

If it is a smart program, it would come on sooner if you just let it idle in the driveway. Excessive idle should make it come on after less piston fires than if the time was spent on the highway. So, it should not be just about piston fires.

However, several threads have discussed the oil light and none have figured out what the program is. I am still waiting for someone who has figured out or found out how the computer weighs all the variables.

 

This is the best I can come up with so far. From the FSM:

Based on engine operation conditions the oil change indicator message will illuminate...

NOTE:

-The oil change indicator message will not monitor the time since the last oil change. Change your vehicles oil if it has been 6 months since your last oil change even if the oil change indicator message is NOT illuminated.

-Change your engine oil more often if you drive your vehicle off-road for an extended period of time.

-Under no circumstances should oil change intervals exceed 6,000 miles (10,000 km) or 6 months, whichever comes first.

 

They use the term "duty cycles" in the manual. A duty cycle is a specific term meaning something is in it's active state.

We know it's not a simple counter that triggers every 3k or 6k miles, for example, so what else could it be?

I know some of the new Hondas use viscosity sensors that tell you when your oil has broken down to a level that will no longer provide acceptable lubrication to your pistons. This could be what Jeep is using, but the term "duty cycle" isn't a very accurate description of this type of sensor.

Likewise, a complex formula that would keep track of rpm's, temperature, acceleration, shifting habits, etc... would probably be described differently.

It must be counting something. If it's not the odometer, it has to be something else that's rotating or moving with the engine... The pistons or the cam or something else before the transmission seems to be the logical place for this to happen.

Someone with one of those service manuals can probably tell you where the sensor is... This would help solve the mystery.

 

Did you see post #8? It is from "one of those service manuals".
It says "based on engine operating conditions". That is more complex than a counter. Since there is no sensor in the pan, you can rule out the viscosity sensor.
The computer tracks all sorts of things about how the engine is working.
Only a Jeep engineer would have access to the parameters for the message to come on.