Modern car oil monitoring systems.

I know many newer cars come with oil monitoring systems that tell you when to change the oil and that these are supposedly more sophisticated than just a mileage indicator, using sensors and other data from the car to determine a change interval. At the same time regardless of miles I've always heard that you should change the car's oil at least once a year. Do these new oil monitoring systems account for that sort of time interval and recommend changing it even if you haven't driven a lot of miles?

In reply to Harvey :

in my experience with chevy, subaru and mazda, some do some don't throw date reminders and i think it largely depends on whether the ecu is date aware. still, i put oil change labels on my windshield as a reminder anyway.

After noting the age (2+ years, 2200 miles) of the oil being tested on a used car I purchased, included as part of the analysis results from the testing house was this statement in response: "Oil doesn't go bad from sitting"... So I've never actually concerned myself about whether they do or don't take time into account. I don't feel any more need to waste my money changing the oil annually, than I do at 3k miles.

The oil doesn't really go bad,  it's the contaminants and condensation that are the problem.  A vehicle that only sees short trips in the city and never gets up to temperature for a long period of time to burn out the condensation will need the oil changed much more frequently than a vehicle that sees all highway miles.  

My Cayman goes by the calendar and the miles. It didn't get driven a whole lot last year (nowhere to go) but it's calling for an oil change based on time. 

I had one engineer from an OEM explain to me the biggest factor in their calculation for when to change the oil is based on how much fuel is burned.  There may be some other factors invovled, but that was the main driver.  More oil gets you a longer interval.

Patientzero said:

The oil doesn't really go bad,  it's the contaminants and condensation that are the problem.  A vehicle that only sees short trips in the city and never gets up to temperature for a long period of time to burn out the condensation will need the oil changed much more frequently than a vehicle that sees all highway miles.  

That's not really true. Oil, with time, does indeed "go bad"*. Once certain indicators (base number, oxidation etc) reach a certain point, the oil no longer offers corrosion and wear protection for the engine and either needs to be refreshed or replaced. That interval is soooooooooo variable on the specific engine, conditions, oil, etc. 

*Bad being determined to no longer provide protection from corrosion and wear for the engine. 

In reply to Woody (Forum Supportum) :

My Alfa does the same thing.

Interesting. So, there are some systems that account for time in addition to other factors. I guess I wonder how much environmental factors exacerbate the time factor. When the car is running there are a whole bunch of factors that the computer can use to determine whether the oil is losing viability, but when sitting there isn't really anything going on except for changes in the environment around the car. I'd assume it matters in some fashion if you store a car in New England temps year round vs in California temps.

bobzilla said:

Patientzero said:

The oil doesn't really go bad,  it's the contaminants and condensation that are the problem.  A vehicle that only sees short trips in the city and never gets up to temperature for a long period of time to burn out the condensation will need the oil changed much more frequently than a vehicle that sees all highway miles.  

That's not really true. Oil, with time, does indeed "go bad"*. Once certain indicators (base number, oxidation etc) reach a certain point, the oil no longer offers corrosion and wear protection for the engine and either needs to be refreshed or replaced. That interval is soooooooooo variable on the specific engine, conditions, oil, etc. 

*Bad being determined to no longer provide protection from corrosion and wear for the engine. 

Mobil claims a shelf life of 5 years for thier oil.  I think that is far longer than the scope of this conversation.   The old 3 months or 3000 miles adage started when we had conventional oil, carburetors, and the crankcase was vented to atmosphere through the valve covers.  With modern engines that are sealed for the most part, efi, and synthetic oil the intervals can be pushed much longer because you don't have the extra fuel breaking down the oil and junk getting in the engine.   But, this stuff is still why you need to change the oil before it "goes bad".

Patientzero said:

bobzilla said:

Patientzero said:

The oil doesn't really go bad,  it's the contaminants and condensation that are the problem.  A vehicle that only sees short trips in the city and never gets up to temperature for a long period of time to burn out the condensation will need the oil changed much more frequently than a vehicle that sees all highway miles.  

That's not really true. Oil, with time, does indeed "go bad"*. Once certain indicators (base number, oxidation etc) reach a certain point, the oil no longer offers corrosion and wear protection for the engine and either needs to be refreshed or replaced. That interval is soooooooooo variable on the specific engine, conditions, oil, etc. 

*Bad being determined to no longer provide protection from corrosion and wear for the engine. 

Mobil claims a shelf life of 5 years for thier oil.  I think that is far longer than the scope of this conversation.   The old 3 months or 3000 miles adage started when we had conventional oil, carburetors, and the crankcase was vented to atmosphere through the valve covers.  With modern engines that are sealed for the most part, efi, and synthetic oil the intervals can be pushed much longer because you don't have the extra fuel breaking down the oil and junk getting in the engine.   But, this stuff is still why you need to change the oil before it "goes bad".

Are we talking a shelf life of 5 years in a sealed bottle in a climate controlled environment? It seems like that's a different metric than oil being used in a car engine.

In reply to Harvey :

I can tell you that there is an Ambulance in Hilo, HI that had 2 year old oil with 2000 miles. All of the major oil properties were clean and good and still ready for use. 

In reply to Harvey :

Correct, my point is I think even a year would be conservative in a modern engine.  Probably longer.  It would need to be changed because of the other factors before time becomes an issue.

Patientzero said:

In reply to Harvey :

Correct, my point is I think even a year would be conservative in a modern engine.  Probably longer.  It would need to be changed because of the other factors before time becomes an issue.

Maybe. Depends on the engine and conditions. A honda turbo 1.5 that gets short runs once a month isn't going to last because of the vast amounts of fuel that ends up in the crankcase. One that is only driven once a month but for an hour on the highway at cruising speeds will be in better shape. 

The point is there's no one answer for all even though we'd like that. Each engine is different and the conditions its used are different. You want true answers? Test. I may know a guy soon for that too. 

In reply to bobzilla :

That's exactly what I'm trying to say.  The other factors; fuel, condensation, contaminants, etc are much more of a factor than just time.

In reply to bobzilla :

Right. The 1.5T doesn't much matter if it's being driven short runs 1x per week or 1x per month... It's going to end up in pretty much the same condition after the same number of short trips, not the same passage of time. Within reason, the variable of time spent not-running is largely irrelevant.  As best I have been able to find, from multiple UOA points of reference, well beyond 2 years is still well within reason... Well, at least for synthetics. I'm not sure if/how synthetic vs conventional does or doesn't effect this.

In reply to Driven5 :

Depending on the fluid you will eventually see additives drop out, especially older cheap conventional fluids. Heavier elements like Boron fall out even with normal use just because. Doesn't hurt anything but the fluid properties will change over time.