Oil Life Calculator Formula

[randomhero439]

Ok here it is. This is the new revised version. The numbers can easily be plugged into an excel sheet to play around with. Here is what I've been using.

Base formula
Mileage = (LN(10) - LN(TBN * Sump in quarts)) / K
K conventional = -0.00025055
K blend = -0.00020879
K synthetic = -0.00016703

Turbocharger/direct injection
Mileage ^ X
X Conventional: 0.94002
X Blend: 0.94729
X Synthetic: 0.95456

"Easy on oil" factor - Generally Japanese 4-cylinder motors
Mileage ^ 1.032242

Hard driving/Racing
Mileage ^ 0.91862


Here is an older version of the formula i experimented with:
Mileage = SQRT((TBN - 2)*Sump on quarts)*1000

 

[Quattro Pete]

Thanks.

So how did you come up with the K factors for different oil types?

Also, how did you calculate time in service in the results that you gave on the forum?

 

[MBS500]

Thanks, will try

 

[tinmanSC]

Awesome! thanks for posting.

 

[randomhero439]

Originally Posted By: Quattro Pete
Thanks.

So how did you come up with the K factors for different oil types?

Also, how did you calculate time in service in the results that you gave on the forum?


K conventional is based on a car with a 5qt sump going 5000 miles on a conventional oil with a TBN of 7.0
K synthetic applies the same conditions but goes 7500 miles
K blend is the split between the 2

The time interval is simple.
Mileage/10000 * 12

 

[randomhero439]

Originally Posted By: randomhero439
Ok here it is. This is the new revised version. The numbers can easily be plugged into an excel sheet to play around with. Here is what I've been using.

Base formula
Mileage = (LN(10) - LN(TBN * Sump in quarts)) / K
K conventional = -0.00025055
K blend = -0.00020879
K synthetic = -0.00016703

Turbocharger/direct injection
Mileage ^ X
X Conventional: 0.94002
X Blend: 0.94729
X Synthetic: 0.95456

"Easy on oil" factor - Generally Japanese 4-cylinder motors
Mileage ^ 1.032242

Hard driving/Racing
Mileage ^ 0.91862


Here is an older version of the formula i experimented with:
Mileage = SQRT((TBN - 2)*Sump on quarts)*1000


Also would like to add something ive been recently working on.

Mileage from BASE FORMULA ^ Z
Z = LN(80)/LN(HP/L)

 

[gonefishing]

I apologize in advance for this question but is "LN" in the formula?

Thanks!

 

[randomhero439]

Originally Posted By: gonefishing
I apologize in advance for this question but is "LN" in the formula?

Thanks!


Natural Log

 

[Gabe]

LN is the natural log.

How was the formula derived??

 

[LeakySeals]

My engines gonna blow up because I calculated wrong! Will you still give us the quality customer service we are accustomed to? Or its this like everything else today, left to robots telling me to press 1 for Spanish and misunderstanding what I say because I have a Boston accent?

 

[gonefishing]

Originally Posted By: randomhero439
Originally Posted By: gonefishing
I apologize in advance for this question but is "LN" in the formula?

Thanks!


Natural Log


Thanks! I can't remember the last time I hit that button on the old Casio!

 

[NMBurb02]

Have you compared this with a factory OLM?

I'd be interested to see the similarities in your calculation [using manual-spec'd oil (dino, semi-syn, syn)] and when the OLM hits 0%.

 

[Turk]

Great!

One question: Any consideration of factoring in starting & running in extreme cold?? It may not be hard on oil, but it's hard on engines and one may not want to extend out too far.

 

[raffy]

Thanks! Just curious, how did you derive these mathematical relations? Are they empirically based using some form of linear regression (or other curve fitting analysis), or are they theroretically based?

 

[SpeedyG75VW]

Hmmm......mileage numbers don't seem to work so well when you get down into the low TBN numbers. With TBN=2.7 I get 460.76 miles with sump of 4.0 and using synthetic. I would think it would be a lot more than that. But hey....I know the formula isn't perfect and it's a good start.
Maybe you can improve on the formula as time goes on!! Thanks for your work!!

 

[Quattro Pete]

The formula is meant for fresh oil. Which new oil has tbn of 2.7?

 

[randomhero439]

Originally Posted By: raffy
Thanks! Just curious, how did you derive these mathematical relations? Are they empirically based using some form of linear regression (or other curve fitting analysis), or are they theroretically based?


Exponential decay. Basically, the half of the half of the half... and so on

Example TBN:
10.0 @ 0 miles
5.0 @ 4000 miles
2.5 @ 8000 miles
1.25 @ 12000 miles
ect ect

The K Conventional value derived from the assumption that a basic V6/V8 engine with a 5qt sump can go 5000 miles on a conventional oil with the TBN of 7.0.
The K Synthetic value has the same conditions applied, but goes 7500 miles.
K Blend is between Synthetic and Conventional

 

[SpeedyG75VW]

Ok...didn't realize this was suppose to be a "one-time" number. I thought you can plug in whatever TBN values you currently have and calculates how much oil life is left....
So if my Valvoline Synpower TBN was 8.7 and after a few hundred miles it was 8.0.....I shouldn't be using the formula to calculate how much oil life is left with a TBN of 8.0?

 

[randomhero439]

Originally Posted By: SpeedyG75VW
Ok...didn't realize this was suppose to be a "one-time" number. I thought you can plug in whatever TBN values you currently have and calculates how much oil life is left....
So if my Valvoline Synpower TBN was 8.7 and after a few hundred miles it was 8.0.....I shouldn't be using the formula to calculate how much oil life is left with a TBN of 8.0?


Sure if you want to reverse the equation, plug in your new TBN and mileage, solve for a new K value!

Whats even more interesting is the difference between Synpower @ 8.7 and Synpower @ 8.0 is about 500 miles.

 

[Quattro Pete]

Hope randomhero439 doesn't mind... here are some of his formulas turned into spreadsheet calculators. It also includes TooSlick's formula as another data point...

Google sheets