Oil usage in Gen 4

And Toyota could be calling for a shorter drain fill with 0w20 in a 0w16 engine because as a thicker oil it could create higher pressures. Which would just higher over time as oil thickens as it ages in the engine.

 

Nope, that's not why. Oil viscosity changes a lot more with oil temperature than with the SAE grade. The difference between SAE 0W-16 and SAE 0W-20 when hot is only 13%. It is because of the fuel-economy requirement on the window sticker. They don't want to cheat like Volkswagen.

 

Well it does according to Toyota in the North American owner manual. But I’m not really buying it. IIRC the Australian OM, while it toes the line on the default oil weight, says a gamut of weights are also ok, and doesn’t change the oil change interval with any of them.

I’d stick with 6 months or 5k miles regardless.

 

Me, too and when I have one that goes over 100,000 it gets changed even sooner...every 3,000 - 4,000. (With the same old, I'm not a believer in "high mileage" oil)

 

I would only use high mileage oil as a last ditch effort with runaway oil consumption. The way the stuff is marketed, you get the impression you're obligated to use it if your car's beyond some number of miles.

From what I've read it's basically a motor oil but with additives, that swell internal-to-the-engine gaskets. And once you start using it you better stick with it, because going back to regular oil these gaskets can shrink back, and your oil consumption will be worse than at the outset.

 

That's not the change I'm referring too.

When heated up in the engine, the oil starts degrading. The various hydrocarbons making up the oil react with each other, forming heavier weight molecules. Eventually, they get big enough to settle out and form sludge. Before then, they still have an impact on the oil's properties. Used motor oil has a thicker viscosity than when it came new in the bottle.

Going on, the clearances of oil passages and the parts that are being lubricated are a fixed value. In a 0w16 engine, those values are smaller than in a 0w20 engine. A 0w20 oil can be pumped through that engine, but it takes more effort. That effort means higher pressures in the system. Too high, and things start to break. As the oil thickens with use, getting a heavier weight oil out of a 0w16 engine sooner than the regular change interval might be a good practice to avoid that breaking.

Climate is likely a big factor.

Back in the early days of the internet, came across a paper talking about motor along with climate, water, and pH. Byproducts from combustion and the oil's own degradation can form form acids with mixed with water. The oil additive package includes acid neutralizers, but it is one of the components that gets used up, which is the main reason to change the oil. More water in the oil, the faster the neutralizer is used up. The amount is a factor of temperature and humidity. Winter might be drier, but the temperatures means water vapor is more likely to condense in the crankcase than escape out the PCV.

For typical car use, the author recommended 3 oil changes a year in a temperate climate. One at the beginning of spring, one at the end of summer, and one between fall and winter.

Heard that, and that the high mileage oil can be on the thicker side of the label weight range.

 

With our 2010, Toyota Canada says 8k kms or 6 months, whichever comes first. I’ve been changing the oil on ours April and October; months have always governed. Our yearly kms now are only around 3000.

 

Again, that's not it. Motor oil has antioxidant (AO) in it, which prevent oil from oxidizing. When these antioxidants are used up, acidity (total acid number) starts rising rapidly and viscosity increasing starts. At that point, the oil is already past its useful life; so, the fresh oil viscosity is a moot issue. You need to change the oil before the antioxidants are used up and viscosity increasing starts.

Mobil 1 Extended Performance has extra AO for a 20,000-mile oil change. However, it does not come in 0W-16. Amsoil—an expensive boutique oil—also has an extended drain interval.

 

Yep, high-mileage oils are a marketing gimmick.

 

Motor oil in the crank case does not stay looking like fresh from the bottle for 10k miles, and then turns black overnight.

Extended drain interval oils also have extra acid neutralizers, anti-sieze compounds, and other additives that get consumed over the oil's service life.

 

Wrong again. Color of the oil has little to do with its condition. It will turn black after a few hundred miles.

Again, also wrong: extended-drain oils do not necessarily have a higher initial total base number (TBN), which would be by putting more detergents. However, detergents increase the sulfated ash (metal content of oil), which is limited by oil specs, and it has been decreasing over the years to protect emission equipment. Mobil 1 EP has the same initial TBN as Mobil 1 as far as I know. AO does the trick. Once the AO is used up, TBN will start decreasing very rapidly and TAN will start increasing rapidly. Having a higher initial TBN has no effect on this behavior, and the point where viscosity increase starts indicates the end of life for the oil. High-TBN oils were popular in the past when gasoline had a high sulfur content so that the sulfuric acid produced in the combustion wouldn't decrease the TBN to unacceptable levels.

Again, the main difference of extended-performance oils are the AO content and base-oil quality. In addition to more AO, they use more of the higher-quality synthetic base oils such as PAO, POE, and GTL, or even Group III+++. Higher-quality base oils oxidize slower with or without AO. The other additives are the same as in regular oil. Changing all additives requires recertification for the oil, which costs millions of dollars, and it is not needed.

 

You may want to rethink that interval.
"Against conventional wisdom, engine wear decreases as oil ages to a certain extent, which means that changing your oil more frequently actually causes engine wear; these findings were substantiated by studies conducted by the auto manufacturers and petroleum companies, leading to drain intervals increased from 3,000mi to 5,000-7,500mi in most domestic vehicles."
https://support.lnengineering.com/uoa-used-oil-analysis/
Behind a pay wall, but one of those studies.
SAE MOBILUS
Oil burning can even extend the oil change interval as topping off adds fresh additives, from what this group of users saw from used oil analysis of Mobil 1. "Based on the results we've got here, we'd recommend 8,000 miles between oil changes on an engine that uses no oil at all, perhaps 10,000 miles on an engine that uses some oil, and 15,000 miles or beyond with a filter change every 5,000 miles."
https://www.brianschreurs.org/neptune.spacebears.com/cars/stories/mobil1.html

Our Mercury saw less than 7500 miles year. Sometimes a lot less. I went with none synthetic oil, and a change once a year.

An oil analysis costs around that of an oil change, maybe less. It'll let you know potential wear, additive levels, and any presence of water, which I think will be the main factor for you.

Wasn't claiming it was a sign of of the oil condition(though look at your chart), but as an illustration of what is going on in the oil. Antioxidants do not keep the oil like new until they are used up. Processed butter might have the same antioxidants in its as used in petroleum products, and it doesn't stay at its freshest until it is suddenly rancid. Neither are acid neutralizers held in reserve until the AO's are used up. It is a dynamic system.

Heat speeds up the oxidation of motor oil. AOs slow it down, but don't hold the rate at zero. Oxidation of the oil is not the sole source of acids. Some are introduced as combustion by products; NOx will form nitric acids, and ethanol can bring in acetic. TBN tends to gradually drop over the oil's service life.

Detergents aren't the only source of acid neutralizers, and there are other important additives that are used up over time which need to be increased for extended life oils. GM's oil life monitor is based on the known consumption rate of a common antiwear additive under different operating conditions of the engine.

 

What you still don't understand is what happens when the AO is used up. Oxidation and acids increase exponentially at that point. Look at the curve I posted above. It is only a gradual effect until the AO is used up; then, it is exponential degradation of oil. That is why extended-performance oils differ themselves by the AO content but not by TBN.

AOs are not simple science as you mentioned in your butter example. They need to be particularly tailored for the base-oil type; otherwise, they do not work.

Detergents are not the only source of acid neutralizers? Yes, they are. They are bases, and that's what neutralizes acids. You cannot neutralize acids with chemicals that are not bases. Calcium detergents neutralize all acids, while magnesium detergents neutralize most but not all. You need both for optimal performance, as magnesium depletes more slowly and does not promote LSPI as calcium does. Yes, oxidation, sulfation, and nitration are the three main events that result in the total acid number (TAN) increasing. Oxidation is typically what drives the degradation of the oil most. That is why Toyota recommends 5,000 miles with conventional oil vs. 10,000 miles with synthetic oil, as synthetic base oil oxidizes slower.

Oil monitors do not measure the condition of the oil. They are calculators that base their calculation on the driving conditions, such as idling, short vs. long trips, etc. They won't take into account whether the oil is conventional, synthetic, extended-performance, etc.

I have seen many used-oil analyses (UOAs), and ZDDP depletion (depletion of "a common antiwear additive" you mentioned) is the least I would worry about, especially in a modern engine oil with less volatile ZDDP, which was introduced after those GM oil monitors were developed. No, extended-performance oils do not have a higher ZDDP content. ZDDP content is restricted by the oil specs, as it is poisonous to the catalytic convertor. Note that ZDDP also has some AO properties in addition to antiwear (AW) properties.

Low-volatility ZDDP technology: Part 1—Engines and lubricant performance in field applications

 

Where did I deny the exhaustion of AO didn't lead to rapid degradation of oil? It is the implication that there is no degradation happening while they are present that I'm challenging, and why I didn't discuss what happens when they are gone.

Neither are they magic.
BHT isn't in motor oil, but it is in some turbine oils, greases, and gasolines. It is also used in some shortenings.

Which is what I said. GM runs their engines in the lab under various conditions, and monitors the oil's condition under those parameters. It was once reported an antiwear additive level was an important metric, but maybe they use something else now that they use synthetic oils. Those that have done used oil analysis report that the monitor's call for an oil change is really close to the lab recommendation. Going back to counting miles after having a monitor is quite archaic.

 

Of course there will be degradation with use. That's what the UOAs are for, where you can see the FTIR oxidation, sulfation, nitration, viscosity, etc.

Here is some real data. As I have seen in many UOAs, viscosity will decrease, not increase, for most people because of permanent oil shear (permanent shear of viscosity-index improver/modifier plastic mixed in oil) as well as fuel dilution. It only increases in very long drains. It will shoot up exponentially when the AO is used up.

 

Looking at the Japanese owner's manual, 0W-16 is recommended for better fuel economy; however, 0W-20 or 5W-30 are allowed if 0W-16 is not available. 0W-20 and 5W-30 are recommended over 0W-16 for high-speed or high-load driving. The oil must must meet the ILSAC GF-6B or GF-6A specification (API SP with Resource Conserving). If I were using 5W-30, I would also make sure to use a full synthetic.

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