@Queen and Country You said,

Do you have any substantiation regards how old oil 'sours' the new? There are untold nooks and crannies in any engine that will never drain.

PS: I don't bake (or brew my own beer), so your yeast comment was lost on me...

 

Do you not make yogurt or cottage cheese, surely you make vinegar, how about wine, no? Same principal, they will acidify on their own, but the process is sped up exponentially by mixing old with new.
Because, the old has a higher concentration of the catalyst than the environment.

Oxidation and acidification is the primary cause of oil degradation.
All the things that destroy it are present in concentration in used oil and then some, the acidity of the oil itself.

Yes there is oil left over in nooks and crannies, and that's why getting as much out as possible reduces the breakdown time- the inverse is also true.

https://www.austincc.edu/wkibbe/lubrication.htm

 

You've inspired me to do a double oil change. Do one, run around for a few minutes, then do another. Castrol Ultraclean Synthetic is $16/5Q jug, so why not. The Mity makes it so quick and easy, I might go to every 1000 miles after this one. A full oil change costs less than one tank of octane booster.

 

RacerX, many including myself do this.
They even make an engine flush for this purpose, works in 5 minutes. Its engine flush plus cheap oil.
I use this Breaks down the viscosity so more of it comes out.

 

Or you could just change oil frequently, so there is no need to waste 2x oil during oil change. Double oil changes is conspicuous consumption (i.e. wasteful). I suggest you at least eat some of what you kill.

 

A small amount of used oil will cause fresh oil to "spoil?" I don't think so, and have seen no reports to this effect. Acidification is caused by fuel and oxidation, not by a catalytic reaction from existing acid. Old oil dilutes the new, but doesn't spoil it. The dilution is minimal, unless you let the oil get really dirty. Changing the oil every 1000 miles is tremendously wasteful.

 

Oxidized oil will hasten oxidation of new oil.
Oxidized oil will hasten the oxidation of itself
Thats why oil has a lifespan in the first place. And why we make every effort to get the old out instead of just some of it.

From Machinery Lubrication magazine regarding cause of oil breakdown.
"Dirt containing fine metal particles can be a catalyst that sparks and speeds up the degradation process of your lubricant. Air and water can provide a source of oxygen that reacts with the oil and leads to oxidation of the lubricant."

Guess where there is ton of this dirt- in used oil.

I never suggested 1000mile oil changes. I suggest 1 mile oil change with cheap oil to make your good oil last 8 months comfortably.

 

Thers oil in them hills lol

 

Machinery Lubrication looks to have much to say, but I haven't found that quote. "Oxidation is caused by oxygen" seems to come up pretty regularly though, and that heat is the accelerating factor.

Oil should be changed before it is no longer able to do its job. More frequent changes are wasteful.

I have oil analysis data showing that my regimen, largely in line with JLR recommendations, is working well.

 

There are indications that manufacturer specifications on oil change are designed with reducing lifetime emissions as the main goal. Following these will reduce oil changes; a long-time owner I think you would want to maximize longevity of your F-type's engine instead. To do that, you will want to do more frequent oil changes. The question is what "more frequent" is reasonable? Q&C clearly went overboard. I am of the opinion that factory is way too long.

Oil analysis will tell you some information, but not everything. There are carbon micro particles as a result of DI, I know of no lab that tests for this. There is also film strength and so on, with Blackstone you have to pay extra to get these numbers.

I caution you not to treat oil analysis that only looks into contaminants (metals and so on) as a gospel, it doesn't paint the full picture.

 

I made no recommendation of when to change oil- thats between you and your god.
I made a recommendation of how to get the most out of your oil- pun intended.

 

Discarding a worn engine is IMO the most wasteful. So to each his own. Its important to consider that the manufactures' goal is to sell more cars. Think of them like a razor blade company, if they allowed the car to last forever, they'd fold up shop. So their advice at some point must be at odds with longevity or they are not serving their shareholders interests, their true customer.
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To the question of what change frequency is reasonable, the underlying assumption is: shorter is better. It then follows that shortest is best.

 

I didn't fall off the turnip truck yesterday. I see assumptions and incomplete information in this thread, ultimately leading to the Holy Grail of total loss lubrication. I think that's well past the point of diminishing marginal returns with modern lubricant technology.

Initially I wanted to see if the oil was degrading significantly between my usual change interval and the recommended interval. In the Old Days I'd have hit mileage before time with the JLR recommendations, but now I'm hitting time first.

Carbon particles from DI are the known unknown. I'm not sure where the first failure mode indications will come from on that front.

 

Just a few of the glaring inconsistencies one finds regarding the question of oil weight and refresh:

• Castrol's main webpage citing the winter start-up viscosity as the measure of their primary "fuel economy" line. Q: What does start-up viscosity have to do with fuel economy? A: nothin.
• When I grew up, common wisdom was: follow the charts, there was no manufacturer brand recommendation. The charts say, to this day on Amsoil's website, do not use 5W-30, use 10W-40, if you expect ambient temps above 60F before your next change. Q: What does ambient temp have to do with liquid cooled engines controlled by a thermostat? A: Crickets.
• When BMW was aligned with Castrol they recommended 5W-30. Then they certified Mobil 1's Eurocar oil, which is only sold in 0W-40. Now they recommend Castrol 10W-60 for M cars. Q: WTF?
• Porsche has consistently increased their oil weight recommendation as cars have become more modern. Especially when boosted. Q: Why? A: (generally agreed) Higher film strength. Q2: What happened to the better flow story used to previously recommend lower weight oils? A: Crickets.
• All of the measured viscosity vs engine temp charts that I've seen show dramatically different viscosities until 100C, then they are all within 1% from SAE 20 to 60 weight. Q: What is winter weight measuring if not this?
• Half the websites say lower weight prevents wear, since startup drives the variable. The other half say the higher film strength prevents wear due to less metal on metal contact when warm. Q: What does the SAE rating have to do with start-up visvosity? Shouldn't 5W-20 and 5W-40 startup the same?

So the confusion isn't among users IMO, its among manufacturers who can't decide if they want long engine life, shorter engine life, better start up, better mileage, lower emissions, or lower maintenance plan costs through fewer included oil changes.

 

From what I read - chain tends to be taking the brunt of damage from this. However, I can't imagine it isn't also degrading any oil film based bearings.

 

RacerX,
The big thing nowadays is soot-loading.
It caught everyone off-guard. There was zero existing knowledge on this subject. With DI we truly went where no man has been before.

Many universities and scientists are involved in this study now. But they discovered a few things already.
DI was making diamond* nano-particles. This cannot be filtered. So it changes the viscosity of oil- especially the start up viscosity.
The oil you start with is not the oil you end with.

Everyone scrambled, particulate filter on the exhaust. Special testing for wear on chains. Special testing for oil breakdown.
Then there was another parallel factor- carbon buildup.
I stayed on top of the subject to protect my investment.
Jaguar did a phenomenal job. All other brands including Toyota have been plagued with problems and even did emergency redesign of DI to not be exclusively DI.
And yes they have been all over the map with oil recommendations while all this info was coming out. BMW, Toyota, retracted and cut in half their OCI.

*Diamond which is carbon under pressure, this is similar in cutting strength and not to be confused with similar carbon soot from diesel engines formed under much lower pressure and atomization.

 

I totally agree with your conclusion that absorbing soot is going to limit oil effectiveness. While that might be new to material scientists who ride their bike to work, its certainly not a new concept to common sense car owners. Along the same lines, oil filtration tests have proven consistently that great filters catch ~15 microns and higher. Metal particles suspended in oil resulting from wear are generally 5 microns and lower. So you have both soot and wear degrading purity. My opinion is that the WWII generation changed the oil to filter it because the above is common sense they did not design filters into their systems because typical oil filters do not address pulverized metal nor soot build up. Modern studies are only now proving common sense is and always was, common.

My takeaway is, the more you change your oil, the better it works. The frequency is determined a cost tradespace weighing maintenance cost vs longevity. Since I am unconcerned with costs that amount to a half-tank of gas every few months, only longevity is a consideration. Plus, I am not enamored with the new F-Type's direction, so I need mine to last.

 

Did not know that, Thanks.

One thing about your regiment, oil has another purpose these days, cleaning. You will be cleaning your engine more than others.

 

Never heard that one before. As Lizzardo mentioned, excessive heat will oxidize oil.

 

I have to deconstruct a lot here. You are totally worth it, you have made the same 3 choices of vehicles. For you empirical data.

Oil will oxidize in its sealed container just sitting on a shelf. I have checked with the manufacturer of my favourite oil, its 2 years- (I buy it on sale).
But you need proof now. "This oxidation process has the potential to begin almost spontaneously for even oil sitting dormant in a storage container. However, the rate of additive depletion and base oil oxidation generally correlates to the intensity of pro-oxidants existing within the oil."
From Machinery Lubrication https://www.machinerylubrication.com...idation-stages

So the premise that oil needs excessive heat is dangerously misleading due to being partially true.
From an oil analysis tutorial "Oxidation. This is a process that is very dependent on temperature, contamination and the availability of oxygen. It is aggravated when the lubricant is contaminated with raw fuel (e.g. containing unstable olefinic components). Furthermore, the catalytic activity of wear metals, such as copper and iron, can accelerate oxidation." https://www.cimac.com/cms/upload/Pub...ndation_30.pdf

Now for the eyeopener. "it takes less than 5 percent oxidized oil mixed with new oil to reduce the oxidation stability of the new oil by more than 90 percent"
They use a better example than I did of starter yeast "You might think of these reactive chemicals as an infection. It’s like sending nine healthy people into a room with a person ailing from a contagious disease. The good health of the nine doesn’t cure the disease of the one. On the contrary, you end up with 10 very sick people. Any time a lubricant is oxidized (e.g., a viscosity increase, dark opaque color, elevated acid number, pungent odor, etc.), a complete system flush is required to purge the infection."
The following is a very good read, on multiple levels including double oil change. https://www.machinerylubrication.com...me-oil-changes