Calculating OCI

[altaylar]

I too have placed faith in the Honda monitors. My last GM car was a 1976 Chevette, so no experience. I do think suggesting that the Honda OLM's are driven by much of an algorithm is generous. I find that they are entirely predictable, more or less driven by mileage, and very hard to parse. For example, in one Honda we currently have, the monitor goes from 100% to 90% in 300 or so miles. Then, every remaining 10% increment gives you 750 or 800 miles. You might think that that increment would increase with highway mileage, but it doesn't. Still, no complaints. I change that oil usually at about 20-30%, somewhere a little over 6,000 miles, but could not see anyone getting in much trouble following the OLM. Just not thinking that there is much going on in the OLM's "brain."

Sounds like Honda just approximates the oil's condition from milage. I wonder why that initial fast drop in 300 miles. Chevy has a better system I believe.

 

[Patman]

I too have placed faith in the Honda monitors. My last GM car was a 1976 Chevette, so no experience. I do think suggesting that the Honda OLM's are driven by much of an algorithm is generous. I find that they are entirely predictable, more or less driven by mileage, and very hard to parse. For example, in one Honda we currently have, the monitor goes from 100% to 90% in 300 or so miles. Then, every remaining 10% increment gives you 750 or 800 miles. You might think that that increment would increase with highway mileage, but it doesn't. Still, no complaints. I change that oil usually at about 20-30%, somewhere a little over 6,000 miles, but could not see anyone getting in much trouble following the OLM. Just not thinking that there is much going on in the OLM's "brain."

I think that Honda’s oil life monitor is more sophisticated than you think, with the other tenth generation Civic owners I have talked with some of them see the oil life hit zero well before 5k if they drive the car hard most of the time. And then guys like me who do a lot of highway end up seeing it go more than 10k before it hits zero. Mine also counts down faster in the winter as well.

 

[TiGeo]

Works out to around 7500 for me in my Sportwagen. BITOG fact check says....

ACCURATE

 

[mikeduf]

My 2016 Toyota 4Runner used to have a hour indicator of how long you were running on your last oil change. This was an excellent indicator for my severe conditions that I drove. I got pretty good at looking at the hours.

Regretfully sold it and bought a Toyota RAV4 hybrid which has no tachometer and no hour indicator of engine running time. Cars are definitely getting cheaper in a lot of respects for people that want to know.
Marketing seems be about 10,000 k for your oci or, go 20,000k

For me I don't give two craps about mileage, it's all about engine running time for me.

But now I can't even check that unless I become a time recordings and mileage counter.
My oci interval is 3K and I'm loving it. Just my two cents here; I'm out.

 

[dnewton3]

It's because we calculate fuel economy in miles per gallon, not miles per quart, and we describe oil pan capacity in quarts. However if you know your oil pan capacity in gallons, then you can save yourself that little bit of arithmetic.

I first saw this formula described by @Hohn here.

OP could have just said "change your oil after you've burned 200x your oil pan capacity in fuel," but he rightfully likely realized that calculation is probably beyond the average person's math ability, so he wrote out the formula to make it easy and show how he arrived there, and you guys assume the worst. Didn't your math teachers make you show your work? If he just used 50, you guys would be saying "why 50?" smdh Everyone's a critic.

Oh, I understand the math. It's called factor-labeling. But the reality is that you end up with a desired constant ... "50".
It's stupid to write it as "200 / 4" when you can more succinctly just type "50". The implication is already factored in; the goal of an OCI is to be stated in "miles".
And his formula only works for imperial units. Otherwise there'd be other factors for the metric conversions.

It's no different than when we gearheads calculate HP.
HP = torque x rpm / 5252
HP is only valid for any one stated rpm where the torque is measure (which is often left out of most conversations and power claims).
To calculate HP, there is a very complex formula involving radians, rpm, etc. So we just simplify the constant denominator to unitless "5252" ...


My point being that if one is going to leave out all the labeling factors and units, etc, why not just type the result of the quotient? 200 / 4 = 50
Just type the freakin' "50" and be done with it.

 

[TomYoung]

I think that Honda’s oil life monitor is more sophisticated than you think, with the other tenth generation Civic owners I have talked with some of them see the oil life hit zero well before 5k if they drive the car hard most of the time. And then guys like me who do a lot of highway end up seeing it go more than 10k before it hits zero. Mine also counts down faster in the winter as well.

Maybe. Not my perception though through 5 cars so equipped….

 

[Sumboodie]

More accurate to track my hours than miles.

It might sit idling all day while im out cutting wood (place to warm up). That's equal to somewhere around 400 miles but 0 is recorded.

A week of that is 70 hours, 2800 "miles", but 0 recorded.

250hrs ~ 10k miles

My work truck for example has 29,000 miles, but around 11,000 hours.
The other one just over 16,000 miles and almost 3000 hours.

 

[Gladiator007]

OCI(Mile) = (Quarts x 200) / (4 x (Miles / Gallon))

In this formulae, OCI is inversely proportional to 4 times the mpg. In other words, the better mpg, the lower the OCI. In other words, a Prius needs a lower OCI than my Gladiator. What sense does that make? Something is wrong in the formulae.
And don't get me started on the units of variables in the formulae. You have quarts, gallons, and miles. And you end up with just miles. Where did quarts and gallons go?

 

[Fa24wrx]

Ehhhhh ... Why "200 / 4"? Because "50" was too easy?

(5qts x 200) / (4 x 25mpg) = 10?
You could also write it as 200 x qts / 4 x mpg

5qts x 50 x 25mpg = 6250

 

[Plumb Bob]

A (series of) UOA, imperfect as it is, is a useful tool for determining OCI.

 

[dubber09]

IMHO, take severe number as a starting point, if it's too short in your opinion then try extending by a reasonable number. I find that severe is pretty much spot on for both our cars, one is a GDI and the other sees lots of short trips.

 

[Astro14]

(qts x 200) / (4 x mpg) = X

With brackets it makes sense. The 50 instead of 200/4 guys need to go back to school.
If you remove the brackets and then follow BODMAS then 50 makes sense. With brackets you don't get 13,000 miles. This formulae is all over the place. You need to fight the correct formulae.

It makes no sense with, or without, brackets, because it fails to account for operating conditions. Those of us who do know math, and the order of operations, knew that the formula was written incorrectly, but that doesn’t affect how irrelevant the formula actually is.

A short-trip car driven in the city is a lot different than a car operated mostly on the highway.

 

[Gladiator007]

It makes no sense with, or without, brackets, because it fails to account for operating conditions. Those of us who do know math, and the order of operations, knew that the formula was written incorrectly, but that doesn’t affect how irrelevant the formula actually is.

A short-trip car driven in the city is a lot different than a car operated mostly on the highway.

Put engine oils and cars on the side for a moment, this is not even a proper formula. It's not a proper equation, it's not math.

 

[Gladiator007]

Newton's Law

F = GMm/r squared
That's a proper equation where F has the correct unit, 1 kg × m / r squared.

In the above OCI formula, OCI gets the unit mile while the other units vanish. Nope, that's not math.

 

[oil pan 4]

Came across this formula in, either, a thread here or in a paper. Cannot remember. It works for the vehicles in my fleet.
Probably posted in the wrong forum.

qts x 200 / 4 x mpg =

This is for my Ranger:

5qts x 200 / 4 x 18mpg) = 4,500 miles

That would be 8000 to 9000 miles for my wife's hybrid but any time I test oil older than 5,000 miles the oil is done.

 

[ka9mnx]

That would be 8000 to 9000 miles for my wife's hybrid but any time I test oil older than 5,000 miles the oil is done.

I think this formula is rather old and doesn't take in TGDI or Hybrid vehicles. Also to note, it a generalization and not really meant to be dead on. Just a rough idea of an approximation. It seems to work for my vehicles and closely matches the vehicles factory recommendations. Factory says 6 Months or 7,500 miles. I set them at 1 year or 5,000 miles.

Thanks for your reply...

 

[Jetronic]

Came across this formula in, either, a thread here or in a paper. Cannot remember. It works for the vehicles in my fleet.
Probably posted in the wrong forum.

qts x 200 / 4 x mpg =

This is for my Ranger:

5qts x 200 / 4 x 18mpg) = 4,500 miles

it works out to 10k miles for my MG, and the factory recommendation is 15,000 km. severe service is 5,000 km.

for the giulietta it works out 8k miles and the factory recommendation is 18k miles.