I'd caution Tadge has to say what the car is designed to. He can say why, but it's not gospel. I will tell you, as an engineer, there is disagreement all the time on what data means. Most decisions are made by consensus and sometimes made to capture "edge cases". May times there is variation on what is accepted for a various "standard" requirement across car lines due to what we call EJ - Engineering Judgement. Engineers are actually paid to take imperfect data and test results and make decisions. This is why we get the education we do, but it doesn't make the answer "correct". Like many things there are a "range" of correct answers, obviously some answers are clearly wrong, but that doesn't mean if its not wrong its right or that if its not the "official" answer its wrong.

That being said, Corvettes are subject to more (both in occurrence and duration) "edge cases" versus normal cars. To the point on a Corvette it's not an edge case sometimes. So the engineering team has to factor that in.

That's to say a Corvette is designed, and has a maintenance schedule, that allows you to at any moment go to a track and rip laps for a day. If you're NOT doing that, and don't plan on doing that, you can modify the schedule (or for example put different tires on the car). You don't have to, and if someone wants to change the oil per the recommendation, then fine. You can't hurt anything by doing that. But just because you relax the schedule a bit doesn't make you wrong.

 

Driven LS30 oil for me every 5K miles or 6 mos. Better safe than sorry.

 

FWIW, I've never turned over my maintenance records to anyone when I sold a car. No one asked or cared. Even when I sold my C6. Are some buyers picky? Sure. Are there buyers who are not? Absolutely.

Used car value is a myth. A car is worth what someone wants to pay for it, and until you sell it you don't know what that is. A book value is just that "book value" and its used for insurance and tax purposes on equipment. If you get "agreed upon" value insurance then all you do is say to that company you want "book value" (or whatever number you give them) in case of a loss. They don't care if someone will buy it for that amount they care that its reasonable, and what do they use to verify its reasonableness? "Book value"

 

So if we want to talk about risk, how would you determine that? My OLM said 4500 miles, give or take based on my style of driving and operating conditions. My test results say 6000. Going off OLM, which hacked off time for it sitting for 4 months over the winter, I would be risking it at 6000 which is way past OLM recommendations. OTOH, the lab result for 0W40 Supercar oil says I can go 6000. I would say going to 10000 is definitely risking it for that car being driven the way it is and under the conditions I have. OTOH, I just did a 23 Cayenne with a 3.0 turbo motor using 0W20 Mobil Euro at 10000 and the lab result said it was fine. On the Porsche forums, people will feel that 10000 is excessive and it should be 5000. Why? "I just don't feel comfortable with 10000 mile oil changes.". Well, that's helpful.

Do I believe that the manufacturer's word is "the be all and end all"? Absolutely not, with provision. That provision being that you have some way of determining whether to follow it or not besides your "gut feeling". Lacing that means, I would suggest that following the manufacturer's recommendation is the safest way as opposed to what you feel. I get that engineers can exercise judgement. However, engineers are trained in that field so there is some knowledge behind what they are suggesting. That said, having an engineer do surgery is really kind of out there, IMO. I may listen to your suggestions about my car but there is NFW would I allow you to make changes to my medication unless you are a board certified clinician as well.

 

The question I asked is whether the buyer's appreciation has any value or not. Appreciation, IMO, has a number and not an abstract concept. If it cannot raise the price, it isn't worth much.

Yes, I agree that after the transaction is done, you get to know what your house is worth. That said, How would you know what your "ask" is without doing CMA? I can list it for $800K but if the CMA comes back at $300K, would anyone bite? OTOH, if the CMA is $800K but I list it for $200K, wouldn't I be losing my shirt?

 

That's why "books" exist. The housing equivalent is "comparables". The point was a book isn't what its worth, it's a guideline.

 

Risk is based on data. You do a test. I take aggregate results of the OLM over a sample size which is "my driving", when discounting the time factor. I've looked at the research, and I don't think the degradation due to time is worth worrying about. As I said, I'm an engineer, I'm using my Engineering Judgement to make that choice. If it's good enough for my employer who is an automotive OEM it should be good enough for anything related to automotive, in my opinion. You can choose to not like that argument, but be forewarned if you don't like Engineering Judgement being used, never drive any car from any OEM. Some requirement on some aspect of every car (if not many) are determined to be OK by Engineering Judgement.

 

And that is my point. If you did have some data points and make a judgement, that would be one thing. Making a judgement from "I feel" is another issue.

 

Oil can become full of contamination, circulating carbon conglomerates, creating deposits which leads to wear, All while still having high remaining lifespan and creating reasonable testing numbers on paper. This is the main problem with oil life span monitoring and oil testing. There are engines so full of carbon debris that the minute after you put brand new oil inside it needs to be changed already, with 99.9% life remaining because oil is a powerful detergent for cleaning action and will hold a massive amount of contamination while still testing with a high lifespan 'unused' in many tests.

Manufacturers and oil companies I believe make an assumption that the engine is clean inside when oil is being poured in. After all they cannot possibly know what is inside YOUR engine. They also may assume the engine will need to be replaced by the time the warranty is over, which is fine for their purposes, as it minimizes environmental impact by keeping/leaving all contamination/sludge inside the engine during service by allowing long interval oil changes to the max of oil lifespan rather than engine lifespan. Then the engine is a disposable container of sludge by the end of intended lifespan. The oil doesn't need to make the engine last forever in the eyes of the original manufacturer - even though engines could last millions of miles - the engine just needs to last long enough to be out of warranty. Oil change intervals must be based on statistics involving lifespan, warranty, and emissions. It is not a performance thinking to extend oil change interval it is a money and environmental saving thought process. If you care about a particular engine you will not worry about the cost or environmental impact so much and change the oil more frequently and try to keep the engine clean inside by increasing oil cleanliness and via PCV action. Changing PCV flow for idle cruise wot to increase flow rate and maintaining a slightly decrease crankcase pressure will directly impact/improve oil cleanliness via multiple routes and therefore engine lifespan by reducing oil contamination.

et al;
-The thought process of oil lifespan to dictate oil change interval is *not* a performance or reliability mindset.
-PCV has powerful influence on oil cleaning action during service interval and should be as high priority as any other maintenance such as air filtering.
-Change the oil when it appears dirty no matter how high the lifespan remaining is to keep the engine clear from deposit forming debris accumulating

Oil lifespan talk is alot like oil temperature talk. Sure modern oils will tolerate inane temperatures. That does not mean the engines will, though. If you run a factory brittle piston engine at the high oil temps of a racing engine it will ruin the piston materials even though the oil is fine with the temperature and oil manufacturers will say the oil temp is fine for that oil.

 

So Porsche tells me I change my oil every 10000 miles and you think I should do it every 10 miles? That is 0.1% of 10000 miles or did I miss a decimal place?

That sounds like a lot of assumptions of their assumptions. Still, just because the engine (assuming you are right) can last millions of miles, do you want it to and at what expense of time and money? Will the drivetrain last that long and will the body and the rest of the electronics? Will parts be still available? As a taxi driver, that might be a concern to me. Same as a fleet operator. OTOH, as a normal guy, do I care the car makes it to the magic million miles and MB gives me that grille badge? I am guessing that the few cars that do make the million mile thing are a pretty rare thing. I went 480K and ditched the car with AC failure, fuel lines leaking and rear window regulator broken from age. Body was rotten away and leaiking water and I couldn't afford to spend money to replace the regulator and fuel lines simply because it would be almost $500 in parts for a car that probably wasn't worth scrap metal.

In a diesel car, you are going to be changing the oil before it gets to temperature under that guideline. I'm not sure I want to trust eyes to make that decision. Sure, you are right that the manufacturers cannot know if there is a lot of debris or that most of it has been flushed out with the oil drain but I would assume there is some sort of calculation of the average amount of contaminants.

I'm confused. How much temperature will the oil hold before it cooks off? If the piston is so fragile, maybe that isn't the engine for anyone.

If you run a couple of used oil analysis, I think it will give you a good baseline unless you are dragging the car, in which case, "All bets are off". Come spring, I will be running another analysis with 5W40 at 6000 miles which is the recommended interval for 0W40.

 

I think there is a misunderstanding somewhere. What I meant is when we buy a vehicle thats got an engine full of sludge, or if were previously following 10k or 5k mile oil changes with blind trust, and find it full of sludge at 100k or whatever, suddenly realizing the minute you pour oil inside its already filthy before it has any miles at all. Those kinds of engines are in a terrible place, quite unfortunate. And it happens when they reach 50k to 100k with 5k to 10k mile oil changes now, more frequently than ever it seems now.

For example I have a 5.3L With 240,000 miles, the oil coming out is pretty clean now that I've been changing it and caring for it from 180k, hand selected it out of about 12 engines I inspected specifically for cleanliness in the JY. Its a factory original with now 600rwhp dynojet turbocharged these last 7 years or so, and I change the oil once it starts to get fuel-smell and darker around 2,400 to 2,800 miles to keep it looking clean in and out. This engine will probably see 500,000 miles with minimal maintenance, its from the 2002-2007 Silverado era. There are many engines like this one - the sr20/2jz/RB25 from 92-02 for example. Same pistons and general design. Same mileage capable. Will discuss piston and oil temp below more. If I was doing 5k or 10k mile oil changes it would already have failed and full of sludge, even though the oil would come out with plenty of life left probably. That is the point.

My world is built around 200k miles engines that need to see 400 to 600k miles with original parts. This is my daily routine, nothing strange or otherworldly. The right engine inside does not appreciably wear out when its being maintained properly. They need oil pump, valve related hardware, seals, that sort of thing over time, of course, but this does not require any rebuild or machine work. This was figured out sometime in the 80's for Toyota and Nissan and probably others but didn't become the norm for Chevrolet until around 2002 ish.
The gradual slight loss of compression is helpful in forced induction applications as well, makes them more tolerable to boost it seems. That has been my experience, with engines pushing 150psi to 180psi near service limit run perfect and dont leak or smoke thanks to proper PCV. The key is PCV, knowing how to measure it and support it, most people cannot do that I guess.

Are the parts for a 2007 L33 or 2002 LM7 Still available? Yes currently those 2002-2007 era LM7 and L33 are readily available, including the low mileage engines, their computers, aftermarket support, and so on, as well as 4l80e transmission and brand new six speed specimens which support the 600 to 900rwhp I desire from factory internals at this displacement with reasonable fuel economy. A $50 computer will run it in flex fuel with 200lb injectors for example. And if it does not, there is always haltech, aem, MS, pfc, etc... aftermarket ECU options to control engine/transmission as needed. As more advanced units become available , 6 speeds, 8 speed transmissions and so on, they can be retrofitted if desired. I have recently tuned a RB25 with a 8speed automatic for example, its a 25 year old engine with a 10 year old transmission or whatever. They are cheap now. The new parts become cheap and retrofit to the old engine as reliable drivetrain as needed.

If an engine doesn't fall into a specific criterion - easy to tune, easy to swap, easy to maintain, easy to work on, etc... then why force it? The question of reliability is tied to ease-of-use on some level. Technology that drives modern design of the last decade or so doesn't seem user friendly and doesn't add much to performance other than computer control related which can mostly be retro fitted to older example if truly desired. Due to the higher complexity of modern engines I fear that simply maintaining them isn't going to be enough to keep them in service. Keeping the oil clean and engine insides clean isn't going to solve all of the external milieu of controllers and computers that have been added to squeeze that last couple of percent of economy and emmissions out of some power plant which most owners could do without happily. In a big picture way, I believe comes down to spending and luxury - purchasing the latest and most desirable zero miles specimens which are closer to unmaintainable and unfixable than anything previously, and that is part of the price you pay and the expectation is now you have to damn near throw it away once its been used no matter how well its being maintained because the cost and knowledge and equipment to fix it and upkeep is so great for a traditional diy user. Which makes your point extremely valid - for the engines I work on, I would say yes there are many and parts galore still and quite easily to mod and come by. But for the vehicles and engines of recent years, probably no and even if they are , you wouldn't want or be able to anyways.


Of course contamination is calculated precisely given the conditions and emissions for inside an engine. I think It is relevant as part of the oil change interval which keeps those contamination inside the engine to reduce external emissions. Allow me to elaborate...

In the recent years there has been a push to reduce emissions, I think. There have been several technological advancements which improved emissions. After extracting every ounce of efficiency from combustion and EGR and PCV and myriad other devices and technology impacts, And yet still the EPA demanded more. "What can we do to further reduce emissions to meet these guidelines?" My guess is simple: leave it inside the engine. Instead of making combustion ever more efficient, which proves difficult or nearly impossible for the already heavily burdened designs, it is possible to further improve emissions by trapping the emissions in engine oil and keeping it within the engine, essentially trashing the engine by its limited lifespan as a throw-away object along with all its trapped carbon emission footprint this way. When the engine is nearing a decade or two of service with those 5 or 10k mile oil change intervals, the environmental impact has been reduced greatly by changing the oil less frequently and leaving as much contamination inside the engine crankcase as possible, throwing it away with the engine. I think this is the overall strategy for most engines now. The goal is no longer a reliable clean engine after a decade or two - they want a fully polluted engine too complex to repair ready to be replaced with a new vehicle. It seems. tell me im wrong

All engines with factory brittle pistons such as LS engines, RB, SR, 2J engines, all use the same piston materials and all face this issue when being pushed to 3x 4x factory output. For example 500rwhp from a 2L, 750rwhp from 3L and 900rwhp from a 5.3L, for 500,000 miles is easily achievable with a set strict of guidelines I have published several times on forums. One of those guidelines is oil temperature and piston temperature related.I write something here for review
https://www.corvetteforum.com/forums...post1609456580
https://www.yellowbullet.com/posts/74782859/

Oil analysis is useless with respect to pistons of a modified performance application using original internals. There is nothing in the oil to warn you that the covalent bonds inside the piston matrix are snapping like rubber bands. This is an internal matrix-lattice phenomenon and the only way you find out is the piston suddenly breaks a chunk.
Aftermarket pistons is a different story. A forged piston will tolerate a high temperature and large expansion in the bore for which it was machined. The oil analysis for this engine is more useful because you are looking for abnormal wear in parts that are machined non-factory like which is much more common occurrence in those examples and more likely to happen quickly at low mileage whether raced or not. Oil analysis has its place as a tool but does not reveal every thing going on inside the metal materials of an engine that are relevant to reliability, only some things.

 

I don't know where the misconception comes from that things are designed to only last the warranty. That's false. I work in the industry so I can say unequivocally its false.

Parts on a car that are not considered "wear items" and listed in the maintenance section of an owners manual are designed to last 1.5 vehicle lives. A vehicle life is generally 150k for a car and 200k for a truck. This is not the 1970's.

The rest of what you said may or may not be true but sorry, its not relevant because anyone who perpetuates the myth that things are designed to only last the warranty isn't someone who can be trusted.

 

Fair enough but how many sludge filled engines have you run across? Maybe back in the day, I would agree. Barring your head gasket leaking coolant into oil, I haven't heard of too many cases.

So your point is we need to go back to 3000 mile or less oil changes? On the Porsche forums, I keep hearing them say 5000 despite what Porsche says. I have seen no science to prove that it is necessary except "I feel uncomfortable". How do you know it would have failed at 5000 mile oil changes for street driven cars? Again, you push it out of what it was supposed to do and that is a whole different story. What are you basing "plenty of life left" on? Are you saying that if I tested the oil, it would have plenty of life left but still cause sludge?

I did 10K oil changes on an OM606 engine and it lasted 480K which was all I know since I donated the car after that to Rawhide. I had the heads off twice and one of the 2 times was to rebuild and the other was to replace because of a stuck glow plug. After which, I would pull the plugs and use a gun bore brush to get the "carbon condom" that formed around the glow plug causing it to stick in the head.

I do agree that the PCV is important and venting to atmosphere probably isn't a good idea.

You can get parts for the engine and transmission and maybe the ECM if you are willing to work around wiring. I can use one of several ECMs for my 91 C4. HOWEVER, the rest of the stuff, I have to go dumpster diving. ABS module and shock actuators, you have to find a part on eBay and hope it is in better shape than yours. When your infotainment screen fails, I don't see a cheap fix. If you want to bypass the C7 ECM and have a rigged unit, sure. Can you replace the rest of the systems if GM doesn't support it?

And that is my point. At some point in time, it gets harder and harder. We have become a throw away world. Back in the day, you called the TV repair guy to fix your TV if there is a problem. Today, you go on Best Buy's website and find the best deal. Everyone who smoked had a Zippo lighter, flits and fuel. Today, we buy a disposable Bic lighter.

IDK if you are right or wrong. I have not seen evidence to that effect.

That is way out of what we are trying to do so I would say that those guidelines might be fine for an engine which you are trying to make do things it wasn't set up to do.

Maybe but are we doing modified engines now?

 

I would say it is designed to last past the warranty. How much past, I don't know for sure. Conspiracy theorists would say it is designed so you buy a new car but I'd be skeptical since I have seen no such proof.

 

Well, I suggested the oil should be changed when it gets obviously contaminated at least. If we draw that on a graph it would appear probably logarithmic with the longest mile oil changes near the beginning of the engines lifespan and the shortest as the engine nears end of life. There will also be a gray area above the graph shading a region which depends on PCV action and internal engine cleaning tuning/technology. Perhaps I should draw what I am saying....



This is what I imagine for a properly designed late model engine. The new parts with the cleanest starting point will have the least contamination when new and extend the oil cleanliness to high mileage oil changes. Whereas over time the crankcase contamination builds up, which depends heavily on PCV design and combustion sequestration design and spark/combustion efficiency and all of those modern amenities working properly (or not) which influence how much contamination gets into the oil and circulates throughout the oil system. As this happens the engine will depend more and more on the oil change frequency to remove circulating contamination, requires more frequent oil changes.

I feel like you don't actually read what I write the way it is intended. Sorry if I am unclear. I have said several times I depends on engines lasting 500,000 miles. I have said over and over an engine should last 1 million miles. It is clear you are misunderstanding what I have been saying. It isn't that the design is flawed it is that the design is being obfuscated by unnecessary or unwanted technological implements which go against our desires as end users. Not that the warranty has anything to do with that - more like the devices which are unnecessary which wind up failing and causing the average diy user heart ache are unnecessary in the first place for ourpurposes and only there to pass some tests or requirements or behave in an 'advanced' ideology which we would be better off without

 

I see where our thinking ways differ here the most. In my mind, the goal first and foremost is reliability transportation. Items which matter are: engine, transmission, drivetrain, tires, and a chassis that doesn't vibrate or steer poorly at high speeds is nice. The basic fundamentals of transportation needs. From that point, power and economy is nice, but not absolutely necessary. The reason for my thought process stemming this way is an apocalyptic scenario where all you need is transportation. Not luxury or power. Maybe economy. I am a survivalist mindset with a hobbyist aim at getting the most from whatever I have to work with. This often means simplicity is king.

Lets Take a modern engine example. We can begin to remove 'unnecessary' equipment from the engine. Disable the internal injection systems, solenoids, remove the computers, lockout the valvetrain altering mechanisms. The engine at its heart will still run using a carb if needed even if I have to hold a 5gallon bucket of fuel over it to feed it. The oil pump will still work and there are many creative ways to fire the spark plugs but this will prove challenging without any drive mechanism for some distributor which means now I need a computer to interpret signals and fire a driver and it needs to be fine tuned to fire the plug after the driver is activated within a specific time delay which can be many degrees of rotation - it is a control theory problem now, not simply a mechanical one. Thus, those(any) systems in place which replace the most fundamental of transportation queue devices are purely luxury & extraneous until the modern design 'forgets' to include some basic feature that any mechanical operation (computerless) depends upon in any way. In this case, simplicity most likely means that a factory computer is more feasible than anything i could come up with on my own in short notice, so we are back to square one so to speak with how do I get a computer to function while still removing as much equipment as possible that was deemed unnecessary, which was your question I think. Another option is to turn rotation at the crank into some spark distribution system - now the question becomes application. In a hobby scenario the original controls of a factory ECU would be ideal. In an apocalyptic scenario I would not care about having timing profiles for spark so the crank driven solution with some capacitive discharge rudimentary coil for basic transportation would be ideal even if it means constant rpm like a generator. In between these ideas another option is to find a computer which can interpret signals easily for the timing profile application without having to invent and program one for myself - enter the stand-alone ECU, a technological marvel but limited of access for potentially apocalyptic scenarios. It really depends on the application when we start looking at future, specific uses for modern engine/drivetrain support in this way.

The question on computer vs luxury is a kind of 'can of worms' with many answers that depend heavily on why you need or want that specific vehicle or engine to run in the first place. If we wanted a seamless transition away from useless unwanted technology while still maintaining the most economical and power and cleanliness related features often the easiest method is to simply reprogram an OEM ecu and turning off those unwanted features inside it directly, such as with HPtuners, which does exist.

 

I mean I've seen the test methods, confidentiality prevents me from sharing them specifically but in terms of vehicle life I have the proof.

 

I've never heard of a manufacture complain that their cars lasted way past the warranty period but I heard of owners complain that their car failed just after the warrant expired.

Manufacture was happy, owner was not.

Take Madza for example. I owned a first generation rotary engine the R100. Engine failed 2 in 5,000 miles, side rotor seals and tip seals, which was common on this engine. Mazda re-engineered the engine and tests indicated it would now easily last over 425,000 miles. Not acceptable so they re-reengineered the engine to now only last ~ 100, 000 miles. Bingo!

So many manufactures engineer for planned obsolescence, only design it to operate for X amount of time. Too short or too long = bad.

 

I wouldn't say manufacturer is happy. There is a cost of unhappy customers. Its usually greater than warranty costs.

This is why recalls are not all bad. Think about any recall you get out of warranty, its effectively a free fix to something you'd otherwise have to pay for. The product gets better, you pay $0. Or the manufacturer could ignore the problem, refuse to fix it out of warranty and then you're a really unhappy customer. This is why I don't get why recalls have a bad rap. A safety recall, that's different, but something that's more like oh this could be a problem but we want to fix it for you.

Most recalls today are not forced by the gov, they are voluntary.

 

I'd argue you're looking at it the wrong way, and negatively. If a vehicle has a life of a 150k, why would I want something to significantly exceed that. If the vast majority of parts fail at a specific time any parts lasting longer are too expensive.

Cars are a product, its a business. It has a usable life, the most efficient design is something that lasts exactly the usable life. To say this is malicious or planned obsolescence is to put a tone on this that's frankly unfair.

As technology moves things become obsolete. Why design them to last longer than they are likely to be used or desired? Who does that benefit?