Oil change interval

thanx for posting that info, its very interesting

 

I fibbed on my post, above ... the Mobile 1 Extended oil analysis shows it can go another 2-3K - it is rated to 15K. My 2nd sample was Valvoline MaxLife and test analysis showed it had reached it's usefulness at 9700 miles, judging by the TBN value of 1.0. It still had enough additives to go another 1K. Point is I'd be throwing money away changing the oil at 5K.

 

Serious question. How does the analysis determine how much life is left in the oil? Lets say when you do an oil change the oil is at 100% effectiveness. When the analysis says it has 3000 miles left, at what % effectiveness is it at?

 

Look in the thread mentioned above: https://www.tacomaworld.com/threads/used-oil-analysis-reports-2nd-generation-tacoma.182294/

There are a number of oil analysis reports shown there. The reports include the current properties of the oil compared to the specified requirement for each property.

 

http://www.blackstone-labs.com/ <--there are videos on this website that explain how the analyses are done, what the numbers mean, etc etc.

 

The main value is TBN - Total Base Number. From Amsoil website,

"Generally speaking, the higher an oil’s total base number (TBN), the better its ability to neutralize contaminants such as combustion by-products and acidic materials. TBN is a measure of (alkaline) additives in the oil. Higher TBN oils are able to neutralize a greater amount of acidic materials, which results in improved protection against corrosive reactions and longer oil life.

TBN levels are targeted for the intended application. For example, gasoline motor oils typically display lower TBN numbers, while diesel oils must manage the high contaminant-loading from soot and sulfur and typically have a higher TBN.

TBN levels decrease as the oil remains in service. When the level reaches a point where it can no longer protect against corrosion, the oil must be changed.

Oils that are formulated specifically for extended drain intervals typically display elevated TBN to ensure proper corrosion protection for the duration of the extended interval."

From Amsoil...

 

Here is another good article.
http://machinerylubrication.com/Read/29204/oil-base-number

 

Great answer, thanks. I guess that gets me thinking, a new oil with a TBN in the 6-7 range vs a used oil (7-10,000 miles) with a TBN of 1.6-2.5. Is that worth the savings of stretching the oil? It has less protection, i just dont know what that actually corresponds to. Are there wear tests vs TBN?

 

5K miles whether it needs it or not. I'll listen to the toyota engineers

 

i agree, i am 5,000 religiously, just wondering as some have brought up extending OCI. Ive always followed mfrs recs

 

TBN measures how much capacity the oil has to neutralize acid contaminants in the oil. So at a given point higher is not necessarily any "better". All you need is "sufficient". Once TBN becomes "too low" you will start developing acids in the oil and that isn't good for the engine components. As long as TBN is above some number it will neutralize acids. New oil has a very high TBN because it hasn't had to neutralize any acid yet. Over time the TBN drops because it has been exposed to acid. But as long as the TBN is "high enough" it will still neutralize acid. Also realize TBN is not a linear scale, it drops quite quickly from high numbers to moderate numbers and then drops much more slowly.

The question then is what is "enough" as far as TBN goes. Not an immediately easy answer because what the TBN number actually means depends on the type of testing done. The oil manufacturers themselves use one method - which is very accurate but requires using chemicals most people don't want to have around. The oil testing services use a different method that produces different results at low TBN numbers. At low TBN values the oil testing services will report a lower TBN than the oil company method.

The second issue with determining the answer is most research and testing is based on diesel engines and these produce way more contaminants than gasoline engines. So the diesel numbers might be higher than necessary for our gasoline engines.

All that said, the standard advice for diesel engines is to keep TBN above 3.0 using oil company testing. That is about equivalent to TBN of 2.0 for the kind of testing that Blackstone and Wix do. Again, that is for diesel and gasoline could run lower.

Blackstone has decided that 1.0 is the cutoff for their testing with gasoline engines. There doesn't seem to be much rigor to that if you ask them for specifics.

So a very conservative approach would be to use the diesel number as a threshold for our vehicles. That would be a TBN of 2.0 as reported by Blackstone or Wix. And again, remember the scale is not linear so if you went from say 10 to 5 in just 3000 miles it might take another 6000 miles on top of that to get from 5 to 2.5. So you can't accurately extrapolate from a single test and would instead slowly increase the interval as you continue testing.

Lastly TBN is only part of the story - it only tells you if the oil still has capacity to neutralize acid contaminants. There are still other things that would indicate changing the oil even if TBN was acceptably high.

 

Also depends on the environment, and how you drive.

 

Yup, how you use your truck can greatly impact your OCI.

 

I change my oil and filter every 6 months (less than 5000 miles), using Mobile 1 synthetic and a Toyota filter. Every time I change it, the old oil is dark, almost black. I drive my truck easy and not off road. Should the oil be that dark? Maybe I should get it analyzed.

 

What would be odd is if your oil came out the same color it went in lol. It would be great but it would be strange.

Oil is going to be black. Color is not an indicator of spent oil, texture and smell can be. What you don't want is your oil coming out sludgy.

My oil comes out black at 10k and oil analysis says go longer. So I wouldn't worry if I were you.

 

Oil can be black and still function properly.

 

At 3-4K my oil still looks new on the dipstick. It's pretty dark in the pan when you drain it though.

 

Used oil should look pitch black as it drains out of the pan in a thick column of oil. But what does the oil look like on the dipstick before draining? If you can still see through it pretty easily on the dipstick, this should ease your concerns a little. Mine looks pretty bad draining out of the pan but I can *always* see through it on the dipstick, even if it does have a darker color. Now if it's literally pitch black on the dipstick and you can't see the stick at all, that would have me a little concerned.

Dark oil means it is doing its job cleaning the engine and suspending particles (dirt, carbon, etc) smaller than the oil filter can catch.

 

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