Oil Life Increasing With Use

[Bellavita]

I took pictures of my trip meter and oil life percentage at two different times and found I have oil gaining life with use!

On August 4th I had 5,627.7 miles on the oil with 43% oil life remaining.

5627.7 / (1-.43) = 9,873 mile projected oil life​

On August 25th, I had 6,200.2 miles on the oil with 38% oil life remaining.

6200.2 / (1-.38) = 10,000 projected oil life. A gain of 127 miles of life!​

I “gained” this oil life after returning from a 482-mile trip that was 99.9% highway driving. It would be interesting to learn how these OLM algorithms calculate life.

 

[pbm]

I would imagine the OLM assumed that the highway driving you were doing at the time of the increase would be the same type driving for the rest of the OCI. When you returned to your normal driving pattern I assume it would readjust the OLM's oil life remaining.

 

[BigCahuna]

I don't get how a olm, figures out if the oil is in need of replacement. My wife's Chevy equinox, has said to change the oil at 5k miles since we've owned it. The last time the oil was changed was by a garage we deal with. The monitor was reset after the change. But it started showing "change oil soon " message at about 4200 miles. This car has always consumed oil since we've owned it. So about 3 qts have been added since the change, and my wife's driving habit's hasn't changed. So why is it saying to change the oil sooner than in the past ?.,,,

 

[gfh77665]

I don't get how a olm, figures out if the oil is in need of replacement.

The algorithm takes known accumulated data and extrapolates it to arrive at a fluid projection.

 

[BigCahuna]

So why wouldn't it noticed the added 3 qts of fresh oil, and extend the oci, instead of reducing the oci ?. If it can't take the fresh added oil into consideration, what good is it doing ?.,,,

 

[GSCJR]

It doesn't analyze the oil condition, it just determines an interval based on driving patterns and engine data inputs.

 

[dumkid]

So why wouldn't it noticed the added 3 qts of fresh oil, and extend the oci, instead of reducing the oci ?. If it can't take the fresh added oil into consideration, what good is it doing ?.,,,

It knows you've driven x distance at y speed, it doesn't know you've added clean oil. If it has a level sensor then it knows something got in the crankcase but it doesn't know whether it's oil or fuel or coolant or something else

 

[JohnnyG]

So why wouldn't it noticed the added 3 qts of fresh oil, and extend the oci, instead of reducing the oci ?. If it can't take the fresh added oil into consideration, what good is it doing ?.,,,

It doesn't care about how much oil is added. It does care if the oil has gotten hot enough, for a long enough period of time, to burn off condensates.
This article might help you, but it does get a bit carried away with other maintenance items:
https://www.yourmechanic.com/articl...t-service-indicator-lights-by-brent-minderler

 

[BISCUT]

Some, like my 15 F150 5.0 are rather linear and time is a major part of the equation. On extended (12hr) largely highway trips my OLM % barely moves. Leave it parked for weeks/month and it drops.

 

[BigCahuna]

If my wife's vehicle has done anything in the severe service category, I might feel like its something worth having. BUT, since this vehicle has had oil consumption issues from the time we got it (35k miles), and is approaching 85k miles, it's hard to trust or have faith in what Chevy says . They were not interested in resolving the oil issue which is a well known problem, not just with our car. Even their recommended oil to use was useless waste of money. The only thing I found to help, was to mix my own brew of heavier oil. That has reduced consumption. But a engine with that low miles shouldn't need a top off at every gas fill up. So if they don't know how to build a good engine, they can't be relied upon to perform maintenance on it. Adding a worthless toy to it doesn't help anything.,,

 

[atikovi]

If it has a level sensor then it knows something got in the crankcase but it doesn't know whether it's oil or fuel or coolant or something else

I would think smart cars can figure out that a sudden increase in level means the addition of new oil. And some sensors can measure the condition of the oil.

 

[Bellavita]

I would imagine the OLM assumed that the highway driving you were doing at the time of the increase would be the same type driving for the rest of the OCI. When you returned to your normal driving pattern I assume it would readjust the OLM's oil life remaining.

I think your theory is right. I did some digging and found this table on the JEEP OLMs. Simple and it makes sense how they bucket the three driving conditions and associated oil life.

 

[Oliveoil2]

OLM: number of cold starts, heat cycles, mileage, time.

 

[Spike555]

OLM's are a joke most of the time, they base their recommendation on idle time, heat cycles, miles and calendar time.
Most will tell you to change the oil after 12months no matter how little you drove.
I still go by miles, just wish the OLM could be turned off.

 

[Number_35]

There was an interesting post here a couple of years ago, saying that oil life was inversely related to the amount of fuel consumed.

I think the formula was something like:

Take the oil capacity x 200

Calculate how much distance it will take your vehicle to burn that volume of fuel.

That's the mileage at which you should change oil.

Example for our 2007 Dodge Grand Caravan:

Oil capacity including filter = 4.7 l
200 x 4.7 l = 940 l

Worst case:

City driving in the winter: 20 l/100 km
How many km to use 940 l of fuel?
940 l/20 l/100 km = 4700 km

Best case:
Highway trip in the Spring or Fall with no AC use: 9 l/100 km
How many km to use 940 l of fuel?
940 l/9 l/100 km = 10,440 km

Could the OLM be that simple?
The oil capacity would be programmed in, and othe input would be fuel consumed.

This would account for cold starts, idling, cold weather, etc.

 

[dnewton3]

When your driving style and conditions improve, it can cause the IOLM to adjust it's projected lifespan of the oil load. It looks at many things as inputs (see the above posts) and when those conditions become less stressful, the remaining "oil life" is adjusted in a positive manner. The OLM/IOLM systems don't test the oil; they only use multiple inputs and then compare them to a "map" of general oil projected lifespan as set by the OEM. The IOLM systems look at ambient temps, duration of operation per cycle, engine coolant and oil temps, load cycles (light or heavy throttle), etc ... All these parameters are used to determine a "result" of oil life based on a pre-programmed multi-dimensional map.

This phenomenon is no different than "DTE" calculations for fuel range. When a vehicle spends a lot of time averaging "XX.x" mpg, and then you take a trip which alters the driving style (typically a steady state highway speed greatly improves efficiency), the amount of "range" in the DTE (distance to empty) can greatly increase. You might fill a tank just prior to a long trip and the projected fuel range is 380 miles, but as you run those highway miles and get better mpg, the "range" can actually go up (perhaps 410 miles) as you drive. This confounds people who don't understand that the algorithm is constantly adjusting to the average mpg and remaining fuel. I had to explain this to a friend's wife. She literally called and thought her car had something wrong because the DTE kept going up. She typically drives city-only miles, and then took a long multi-state trip.

Both the fuel and oil monitoring systems can be altered by the driving conditions, and either positively or negatively affect the projected life of that condition.

 

[Bellavita]

I think your theory is right. I did some digging and found this table on the JEEP OLMs. Simple and it makes sense how they bucket the three driving conditions and associated oil life.


View attachment 175099

I'd like to add that my Grand Cherokee maximum oil life is 10,000 miles. When the majority of my driven miles are highway without towing, every 1 percent of life equals exactly 100 miles.