How does an oil change reminder work?

[larrymoencurly]

Does the computer just turn on the light after the engine has been run
so many hundred hours of operation? Or does it compensate for driving
conditions, such as decreasing the change interval if a lot of
short-trip driving or hard acceleration is done?

If there's an optical sensor, how does it compensate for some oils
being a lot darker than others even when new? Or do they measure the
capacitance between a pair of plates immersed in the oil?

 

[Roberto Saldo]

Does the computer just turn on the light after the engine has been run
so many hundred hours of operation? Or does it compensate for driving
conditions, such as decreasing the change interval if a lot of
short-trip driving or hard acceleration is done?

If there's an optical sensor, how does it compensate for some oils
being a lot darker than others even when new? Or do they measure the
capacitance between a pair of plates immersed in the oil?

Im not sure it measures *anything*

I will take hours of operation into account, it should use number of starts.
I might use the driving pattern (high revs, low revs).

--
Med venlig hilsen/Best regards

Roberto Saldo, Consultant, System Developer, M.Sc.

"Recursive: Adj. See Recursive."

 

[Girgath]

If I had to guess (And this is a guess) I would say that they use a ....
crap what is the word... spectograph (you know the dealy you use in
chemestry to shine a light through an opject and it reads how many
contaminent entities are flying around...) specrum something... anyways, I
would assume that when it gets to a certain percentage it would turn the
light on. So much less programming then reading short trips and all, and
then it couldn't compensate for outside factors.

 

[Nico Coesel]

Does the computer just turn on the light after the engine has been run
so many hundred hours of operation? Or does it compensate for driving
conditions, such as decreasing the change interval if a lot of
short-trip driving or hard acceleration is done?

If there's an optical sensor, how does it compensate for some oils
being a lot darker than others even when new? Or do they measure the
capacitance between a pair of plates immersed in the oil?

I think they measure the viscosity of the oil at a certain
temperature. From my experience, the oil will get a lot thinner over
time.

 

[stu]

I think you all are giving the auto companies too much credit. I doubt they
would spend any money on a sophisticated system. Probably just mileage from
the odometer...

 

[Pat Ford]

Gm cars with efi use air temp, oil temp, number of starts and mileage. I
can dig up dissassembly code that shows it in a P4 ( late 80's to ~1998) ecm
Pat

I think you all are giving the auto companies too much credit. I doubt they
would spend any money on a sophisticated system. Probably just mileage from
the odometer...

 

[Spehro Pefhany]

If I had to guess (And this is a guess) I would say that they use a ....
crap what is the word... spectograph (you know the dealy you use in
chemestry to shine a light through an opject and it reads how many
contaminent entities are flying around...) specrum something... anyways, I
would assume that when it gets to a certain percentage it would turn the
light on. So much less programming then reading short trips and all, and
then it couldn't compensate for outside factors.

I doubt they use a turbidity sensor, probably just operating hours or
maybe f(operating hours, speed, total elapsed time)- kind of an
electronic version of the little plastic sticky the oil change places
give you.

Of course if someone can point out an oil turbidity sensor as a spare
part on a car that will disprove this guess, at least in that case.

Best regards,
Spehro Pefhany

 

[Roger Lascelles]

I read that the BMW computer monitors number of starts, time elapsed, miles,
engine temperature reached etc to compute when oil change is needed.

 

[steve]

I doubt they use a turbidity sensor, probably just operating hours or
maybe f(operating hours, speed, total elapsed time)- kind of an
electronic version of the little plastic sticky the oil change places
give you.

Of course if someone can point out an oil turbidity sensor as a spare
part on a car that will disprove this guess, at least in that case.

Best regards,
Spehro Pefhany

http://www.speff.com

http://www.gm.com/company/gmability/environment/road_to_future/adv_tech_vehi
cles/todays_vehicles/oillife_qa_041603.html

This link says it's an algorithm for GM.
Steve

 

[[email protected]]

A computer chip monitors, the number of starts, RPM's, running
hours, engine temperature, (and a fifth parameter which escapes
me at the moment,) and does a calculation then illuminates the
light.


mike hunt

 

[Tom Bruhns]

Does the computer just turn on the light after the engine has been run
so many hundred hours of operation? Or does it compensate for driving
conditions, such as decreasing the change interval if a lot of
short-trip driving or hard acceleration is done?

If there's an optical sensor, how does it compensate for some oils
being a lot darker than others even when new? Or do they measure the
capacitance between a pair of plates immersed in the oil?

Though the manual for my car claims the service light comes on based
on severity of use, it's always been at 7500 mile intervals as far as
I can tell. That doesn't mean it couldn't, or even doesn't, sense
things like cold operating time, etc.

The oil level sensor is a float which drives a couple of magnetic
reeds for mine. The original float got "oil-logged" and falsely
indicated low oil when it was hot.

Cheers,
Tom

 

[saeengineer]

A computer chip monitors, the number of starts, RPM's, running
hours, engine temperature, (and a fifth parameter which escapes
me at the moment,) and does a calculation then illuminates the
light.


mike hunt

It would be helpful if we knew the make, model, and year of the vehicle.

 

[Watson A.Name - 'Watt Sun']

I think you all are giving the auto companies too much credit. I doubt they
would spend any money on a sophisticated system. Probably just mileage from
the odometer...

I agree. But the next Q is, how do you reset the light after you do
your own oil change? Do you have to have a fancy terminal to
interface wih the OBD stuff on the newer cars? Or can you just do it
easily with a jumper or switch?


--
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###Got a Question about ELECTRONICS? Check HERE First:###
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Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[E. Meyer]

I agree. But the next Q is, how do you reset the light after you do
your own oil change? Do you have to have a fancy terminal to
interface wih the OBD stuff on the newer cars? Or can you just do it
easily with a jumper or switch?

]

Its different on each car, but I have yet to see one that doesn't explain
exactly how to do it, without special equipment, in the owners manual.

 

[Guest]

I am not sure you are giving them enough credit stu. I don't claim to be the
almighty expert either. I think they measure operating hours, crank
revolutions and operating temperatures at a minimum and calculate useable
oil life from that data.

Cheers,
Howard

I think you all are giving the auto companies too much credit. I doubt they
would spend any money on a sophisticated system. Probably just mileage from
the odometer...

 

[Al Haunts]

Im not sure it measures *anything*

I will take hours of operation into account, it should use number of starts.
I might use the driving pattern (high revs, low revs).

IIRC the GM algorithm for most gasoline engines is 300,000,000 engine
revolutions, minus "penalty factors" for time spent below or above
normal operating coolant temperature. Simple as that.

Regards, Al.

 

[Watson A.Name - 'Watt Sun']

IIRC the GM algorithm for most gasoline engines is 300,000,000 engine
revolutions, minus "penalty factors" for time spent below or above
normal operating coolant temperature. Simple as that.

Well, if you assume an avg RPM of 2000, then that works out to about a
hundred days, continuously running.

I don't have a reminder light, it just says 6 months or 3000 miles.

Regards, Al.

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

[John Popelish]

IIRC the GM algorithm for most gasoline engines is 300,000,000 engine
revolutions, minus "penalty factors" for time spent below or above
normal operating coolant temperature. Simple as that.

Last May I put 12,000 miles on my bike, driving about 10 hours a day
averaging 3200 rpm. That would have be about
3200 rpm * 60 min/hr * 10 Hr/day * 31 days=59,500,000 revolutions.

I waited till I got home to change oil, but all the Harleys along on
the trip got one or two oil changes. If you are right, there is a lot
of good oil being dumped out.

 

[Robert Hancock]

I think the penalty factors likely drag that number down significantly
though. You wouldn't see near that amount of time expire between oil changes
unless you only drove it on very long trips.

I believe they also say not to leave it over 6 months regardless of what the
light does.

 

[saeengineer]

I agree. But the next Q is, how do you reset the light after you do
your own oil change? Do you have to have a fancy terminal to
interface wih the OBD stuff on the newer cars? Or can you just do it
easily with a jumper or switch?

Again, some yes, some no. It depends on the vehicle.

BMW varies the Oil Service and Inspection Indicator lamp system that
uses Mileage, Engine Temperature, and Engine Speed to calculate
'Estimated Mileage' that triggers the lights depending on these factors.

Older fords and Cadillacs used something similar.

I can't remember the last time I saw one that was triggered just with
mileage (but I'm sure it was a model before 87).