This is a comprehensive explanation of what engine oil does, why it needs to be changed at regular intervals, and how to extend its life. It was written in response to a misguided idea that engine oil does not need to be changed regularly.
Engine oil is a finicky bitch. The reason for that is because the source of the oil changes. Every company does something different, so the standardized test actually has nothing to do with the propaganda on the label, and most people ignore it entirely. Dexos (which has a scale of its own), synthetic, and regular oil all have different properties, and the source for the oil changes drastically. Some of all three come directly from crude oil, some come from recycled engine and/or lubricant oils from other manufacturing companies and practices, some come from carbon sequestration cycle plant life (usually referred to as natural... even though they're all technically natural), and some are a mixture of all of the above. The Dexos scale is generally the easiest to comprehend and utilize. It was developed by GM engineers, and has been the standard for essentially all motor vehicles since the 2000s (I think). I've been using it for quite a while, but I've done a lot of oil changes on lots of vehicles and equipment, so I don't remember exactly when I started using the Dexos scale, I just remember that once I started, that's all I used. Many different companies use the Dexos scale, and it's used in many viscosities (0w20, 5w20, 5w30, etc). Dexos is considered a fully synthetic oil, which means that once you use it, or any other fully synthetic oil, you do not revert back to regular (or "standard") oil. The reason for this is because the engine parts have a wear-in cycling period whenever large changes are made in fuel, fuel performance/octane, and lubrication materials. Older engines had grease ports for certain bearings internally and externally, but those have all been eliminated in everything other than commercial vehicles. Working on large equipment comes with a combination of other skills that do not relate to mass produced economy class vehicles, but I'll refer to them in this case for clarity. Even the ball joints and boots of suspension components in economy class fleets have shifted to no-touch for the life of the part. This wasn't always the case. There used to be zerk fittings all over the place on vehicles that required regular intervals of service. That's why the industry called it a "lube job" for decades. Now it's just called an "oil change." However, the greasing portion of a lube job has not, and really cannot, go away from the commercial vehicle industry. For our purposes in this discussion, I'll try to keep those references at a minimum or explain it as I go thoroughly. Just keep in mind that for your purposes, on your current vehicle, "lubing" or greasing is not really necessary. The auto industry has developed a system of management to their vehicles that all but eliminates the inherent inability and misconceptions professed by their customers. That has a lot to do with legal ramifications they've faced over the years from breakdowns and catastrophic failures due to owners changing a process or recommended maintenance interval which resulted in death, then the car company taking blame for not specifying the exact process. The process for determining blame was illustrated in the movie Fight Club. That was his job before he started the club. Anyways, the car manufacturers have tried to eliminate the possibility of terminal breakdowns from lapses in maintenance cycle attention. Just know that it wasn't always that way, and there's many different vehicles that still require the "old way" just to function.
Moving on... I recommend Valvoline Dexos 1 fully synthetic, at whatever viscosity your vehicle and region suggests. My assumption is that you're at 5w30, but it might get a bit colder there than most places so that might dip to a lower scale viscosity. You would know better than I would. The issue in determining the proper oil and at what interval to replace it has to do with an individual's driving habits. Some drive 100 miles a day in cold or hot weather with many elevation changes, and some drive 10 miles a month at sea level on a level elevation. It's very difficult to manage the variables in mass manufacturing, and tailor a specific oil type for every vehicle, and every driver's habits. There's also the issue of air quality, and fuel quality. The gasoline you're using comes from a different crude oil source than people in California, as an example, and might be dirtier or have a larger percentage of ethanol (with its own variability in water content/quality). Every region uses different standards for their refineries, and every company has its own variability in processing, as well as the issue of the crude oil they're using (which is almost always based on price/economics). Basically, there's millions of variables that play into the type of oil you should use, and the standards for making that oil do not take into account every individual's particular situation. So, the decision on what kind of oil, which brand, and what interval you change it at "should be" determined by the manufacturer. Secondarily to that, the regional technicians have a better understanding of weather, elevation, gasoline quality, etc for determining a better oil for any given situation. Take that with a grain of salt, though. Some chain stores are pushed to sell certain brands for kickbacks. A Walmart technician might prescribe an entirely different approach than a "Bob's Country Oil Change" technician. The only way to wade through the bullshit is to educate yourself on YOUR particular situation; your vehicle, your driving habits, and your budget... as well as your capabilities and work ethic/how much effort you're willing to put into this. Point is, there's no definitive standard for everything because there's just too many variables.
When it comes to people that say "Americans change their oil too much," that strikes me as the same intellectual capacity as someone who says "ethanol is bad for cars." It's extremely and grossly oversimplified with a tinge of arrogance about a subject that the person professing it has multitudes of ignorance about. Not only in knowledge, but also experience. I'll start by saying that the standards for fuel and engine oil may vary in Europe. They certainly vary in places like China and India, but if European standards for fuel and oil are superior to that of the United States as a whole, based on an average, remains to be seen. One thing I can definitively say is that the bulk of my knowledge on this subject has a foundation from standards set by the California EPA. Granted, that organization has suffered extreme setbacks during my lifetime in corruption and the ever present Affirmative Action ridiculousness that has lowered standards across the board, but I studied this stuff a lot in my childhood before the bullshit really eclipsed the science. One of the standards I've used as a baseline to build upon my direct experience with being both a professional mechanic and hobbyist, came from a book called Lives Per Gallon, written by Terry Tamminen. Prior to that, the bulk of my knowledge on this subject came from firsthand experience. Rebuilding engines on F/A 18s, cars, military equipment, and my job at OI. I had a lot of experience, but the science inherent to crude oil and gasoline manufacturing processes and carcinogenic waste was spotty. Hydrocarbons, and all their various forms from ethanol to crude oil was not really a primary concern of my self education. I'm just trying to give you an understanding of how my understanding came to be. You always have to discern not only why someone is telling you something, but how that someone learned what they're professing. I'm not a petroleum engineer, but petroleum engineers usually lack the firsthand experience of their profession. I like to think I'm very well versed in hands on applications with a substantial amount of learned knowledge to compliment that experience. Think of it like the Christ nomenclature. Neither Jesus nor myself are "God" in the flesh. During our realization, it's not a stretch to make that distinction, but I digress. One can view humanity's maker/God as the architect. The Amen are the engineers, and Christs are the machinists. The reason for that is because the distinction between the 3 have a different viewpoint of the intricacies involved in each process. Humanity's maker might be capable of doing everything that the Amen or Christs do, but that's not his job, nor should he be in the position to have to do the more menial labor involved. His purpose is much more superior to that of completing his own prescribed tasks. It's beneath him, essentially. That said, even though the machinists/Christs in that order are subservient to the order, there is a vast amount of knowledge that can be obtained from humanity's maker/the architects. I'm hoping this is giving you a good reference point for what's being said. I'm not trying to profess that I'm a certified petroleum engineer and just wanted to make that clear. However, just based on the statement made by your Irish friend, I can definitively say that he is not a petroleum engineer, nor does he have any basic skillset that would allow him to even have an opinion on this subject. In the order of things relative to this subject, he's outside of the order entirely. As a mechanic, I wouldn't trust him to wash the windows. Just saying...
Dexos is a series of tests performed by GM for all brands of motor oil, and the individual batches that get made. There's hundreds of tests that get done. A few of note have to do with temperature. The hotter oil gets, the more viscous it becomes. The colder it gets the thicker, or less viscous it becomes. That temperature range changes the inherent ability to coat cylinder walls, lube valve stems, and maintain bearings internally, along with crank and camshaft control. Too hot and the oil doesn't properly lubricate, or burns off and becomes exhaust. Too cold and the resistance causes difficulty in compression, or all out inhibits movement. There's tests done in every conceivable way from the coldest temperatures on Earth at the lowest elevation, and the hottest operating temperatures on Earth from the highest elevation. Elevation plays a part in viscosity in the same way water boiling temperatures change due to elevation. The higher you are, the less resistance because pressure within the atmosphere changes. Engine oil is no different, and thusly, by using a vacuum chamber to mimic atmospheric pressure standards at any given elevation, those tests are done to grade engine oils. As you can imagine, there are hundreds, if not thousands of variations inherent to just those tests alone. Next, comes fuel quality. The majority of people worldwide use regular, octane 87 gasoline. As we've discussed, there's lots of terpenes and other additives dumped into that fuel that changes its dynamics. Additionally, there's lots of people that use higher octane gasoline when it's not necessary. GM tests the variability of gasoline types from all over the country, and of all octane ratings before they give their Dexos 1 seal of approval. What they're testing for is how the oil will absorb the contaminants in gasoline, for the life of the oil change interval, and continue to properly coat and lube all the internals. For reference, there are points where lubing valve stems and crank shafts is easier for the oil to accomplish, than coating cylinder walls and assisting piston rings in the compression cycle. The tests are conducted to find the first breaking point of the oil. Where exactly that happens isn't the concern. The point is to find the first area that the oil stops being optimal for lubrication. Usually... that's within the cylinders, but that's not important. That is unless you devise an engine system that has different oil reservoirs for every section, which would in and of itself be an engineering nightmare. Anyways, the fuel tests are usually standardized for the shittiest gasoline being used, which is the most common practice, as that's what the engines have been designed to accommodate from the octane rating of regular gasoline. Nevertheless, those tests do test all variables, but generally speaking, the better the octane, the cleaner the fuel. The standard is based on the lowest common denominator, though. Next comes air quality. Air filters remove solids that can foul engine components, but they do not remove gaseous state chemicals. Those concoctions of contaminants also vary greatly depending on the region and elevation. The most prevalent chemical is water. Humidity changes drastically all over the world. At operating temperatures, humidity can solidify and attach itself to the detergents and chemicals used in motor oils. Plus, during bouts of time where the vehicle is not operating, condensation can build up during those periods. All of it, eventually ends up in the engine oil. Besides what gets trapped by detergents and desiccants within the oil, most of that water coagulates beneath the oil in the reservoir. That said, the oil gets tested by GM in hundreds of scenarios that put water into every oil function before they get the Dexos seal of approval. Next is longevity when mechanical failure occurs. This test is done at every conceivable stage between fresh oil, and well beyond the scheduled manufacturer's interval. It's the most simple test. If the oil pump fails, no oil circulates. If damage occurs to the oil pan, the oil drains completely. If there's an oil leak, or the reservoir lowers (which is what you're dealing with). The test involves running an engine at idle, and at all stages including redlining, then draining the oil to see how long the oil continues to lubricate until seizing or mechanical failure causes catastrophic damage. There's also the longevity issue. This is a test that determines how long the oil can sit without the engine running, while dealing with environmental effects, while still retaining the ability to lubricate effectively. All of these tests are done while using a wide variety of filters, all of which also have different make ups. The vast majority have a cellulose base. Kind of like cardboard with graduated sieves that trap contamination and allow oil to flow. The upper end filters use fiber glass, or they're reusable with ways of deconstructing and cleaning between changes... but most of these upper end filters are usually more of a pain than they're worth, unless you're racing. Needless to say, the Dexos certification utilizes the most economic and financially viable option as a baseline, then uses that data to formulate a basic interval strategy that works for all variables across the board. There's a lot of other tests they do, but you probably get the idea. Additionally, this is a system of checks and balances that span across many different companies. It's very difficult to fudge any of that data.
There's two main components that affect oil life. Those are temperatures, and contamination. To understand the complexity of temperature's effects on engine oil, it's easier if you have a background in cooking, or more specifically, deep frying. Normally temperatures in cooking oil are kept between 350-400 degrees Fahrenheit. In my experience, heating and recooling every day allows oil at that temperature to last for about a week. After that, it becomes volatile and difficult to manage on a consistent basis. Sometimes the oil won't cook well, and sometimes the oil burns shit. That's a process of the natural thermo cycling. The molecular structure starts to breakdown and fails in trying to remain constant. Some of the oil stays viscous while other molecules coagulate and harden. That means that portions of the oil absorb and retain a significant amount of heat, while other portions block the heat from the center of the globules. It's essentially impossible to maintain a constant throughout the entirety of the oil because when the oil was growing in its plant stage, different portions of the oil grew at different rates. When new oil is manufactured, all of it is mixed together. In order to achieve a perfect normality between all oil molecules, you'd have to inspect each and every molecule individually... and that's ridiculous to even fathom. Some molecules are small, some are large, some are just right, some have larger hydrogen molecules than carbon, some have volatiles attached, etc. All of these factors play into the overall quality of the oil, and its lifespan regarding temperature. The same is true for engine oil. That's why batches are checked, and the company's first run of a product is not taken at face value as an industry standard. Source oils are constantly changing, no matter where they come from, be it crude oil, or plant based extract oil. The biggest problem for temperature concerns is turning the oil into sludge. That's when the molecular structure starts to coagulate and form very dense molecular bonds. That causes the oil filter to clog up, the oil ports start to plug up, and in severe cases, can cause valves to stick open. I've seen entire heads caked entirely of sludge. That's very bad, and the cause is always the longevity of the oil change went way beyond the interval. Another factor that plays into sludge is contamination; the second most frequent oil breakdown problem. For the most part, the bulk of contamination comes from carbon that converts during ignition, sticks to the wall of the cyclinder, then cycles with the oil into the reservoir. This is why oil is black when you change it: carbon from the fuel igniting. There's also the addition of terpenes that do not combust during ignition, the volatiles that are in them, along with the chemical shit in everyday air taken into the intake. A lesser concern that grows with the odometer, is the breakdown of the metallic components themselves. Tiny shavings accumulate over time. Usually, there's a magnet that sits on the bottom of the oil plug that attracts these shavings. It's good practice to inspect the oil after changing it to look for metal shavings regardless if there's a magnet or not. It's a good indication that some internal engine component is about to go kaput. When we used to race in my teens, we would cut the filter in half and visually inspect it, AND use a magnet to see if something was breaking down. Metal, even very small shavings, can wreak havoc on an engine, especially the cylinders. This threat increases with higher mileage cars, which is why synthetic oil, and high mileage formulas are recommended. Engines wear over time, so what was good for your car brand new, post breaking in, and high mileage are all different and should be treated as such. The extra dollar per quart could save thousands in costly repairs later. Contamination is a problem that affects not only the quality of oil during the oil change interval cycle, but also can ruin parts. Oil pumps have to strain harder the more plugged the filter becomes, and as the viscosity changes. The goal should be to create the best equilibrium possible with all factors in play. A steady oil change interval cycle, and fresh oil keeps the possibility of breakdown as low as possible. It's difficult to judge all factors, and sometimes shit just breaks no matter how exact you are with maintenance, but oil changes are your best bet IN AN ICE SYSTEM RUN ON GASOLINE, to extending the life of your vehicle. Anyone who says oil changes are not necessary... is full of shit, and if they say regular interval oil changes are not necessary, don't buy a car from them.
Extending Oil Life
Now that that's been covered in a somewhat rushed and crash course kind of way, I'll give you some examples of how to extend oil life... although at this point in your car's life, they're not really applicable. Ethanol, when used from the beginning nonstop, without denaturing the ethanol, can extend the life of oil dramatically. 2-3 times as long as with using gasoline. That's due to the extremely low contaminants, and if done correctly, when 100% anhydrous ethanol is the standard, water infiltration is a nonissue. There will be carbon build up, but the majority of the carbon will come from the air intake quality. Ethanol burns extremely clean, plus the majority of the fuel is burned during ignition. This will keep the oil fresh and clean for much longer, and cut down drastically on temperature fluctuations. My guess is that in a pure anhydrous ethanol fueled vehicle, oil changes could go 25,000 to 40,000 miles depending on the environment the vehicle operates in. Plus the entire engine inside and out, particularly the exhaust system would last much longer. Soot and debris from the fuel would be essentially nonexistent. Next is hydrogen alone. Using pure hydrogen would all but eliminate entirely the contaminant issues. You would still be dealing with the air intake quality, but hydrogen is not a hydrocarbon so carbon itself would not be a part of the equation. This might create a false sense of security, though, because the engine oil would look brand new throughout the life of the oil interval. You would still eventually deal with thermo cycling breakdown, but it would take a while. I'd assume this would be an oil life cycle that would last upwards of 30,000 to 50,000 miles. Next is HHO, Brown's gas, or oxyhydrogen. All the same thing, just different nomenclatures. This is special because the oxidizer is inherent to the fuel itself. No need for an air intake, but it is recommended. That's because stand alone HHO burns extremely hot and can melt through most pistons fairly rapidly. This is the fuel Stanley Meyer used, and what John Kanzius used. Direct water to fuel. There is no danger of contamination at all to the engine oil. It will run indefinitely and look brand new the entire time, start to finish. Thermo cycling is an issue, but if done correctly, that might be a non issue. Stanley Meyer used nitrogen to regulate the temperature of the HHO burning within the cylinder under combustion. I'm not sure if he had an on board tank of pure nitrogen, or just used a regular intake similar to how a conventional engine operates, but I do know he regulated the extreme heat with nitrogen. I've contemplated this before, and a standard atmospheric oxygen generator is all that's really necessary. What they do is use Zeolite (same as an ethanol water sieve) to compress atmosphere to a certain pressure. The heat from that process expands the molecules. Oxygen is larger than nitrogen, so the sieve absorbs the nitrogen and funnels off the oxygen. After the oxygen is funneled off, the pressure releases and the nitrogen exits the sieve. One could fashion a device that captures the nitrogen and feeds it into the fuel line of an HHO vehicle to regulate flame temperature. However, this would expose the combustion sequence to a minute fraction of CO2. You could use an on board tank of pure nitrogen, too, instead of regulating atmospheric nitrogen on demand. It would depend on the application and what works best for the operator. Essentially, other than the thermo cycling issue, which would also be drastically reduced by dialing in nitrogen enrichment, the vehicle could (in theory) run for the entire life of the internal components without ever needing an oil change. I mean, there's just nothing there other than engine wear (which would also be drastically reduced because there's no containment present to cause marring) that has the ability to contaminate. Water might be an issue with hydrogen and HHO because under the combustion sequence, that's what burning those fuels make: water. However, at operating temperatures in an internal combustion engine, water evaporates. So, the overwhelming majority of water made would be in a gaseous form, and thus would get expelled as exhaust. Something to consider, though. Another thing you could do is convert to natural gas. It's almost entirely devoid of terpenes and other solid contaminants, but everything else is in play, including carbon saturation. It would extend oil life. Don't know how much better, but it would be an improvement. As far as liquid fuels go, diesel is the worst, and gasoline runs a close second to being the worst fuels for requiring oil changes. There are ways to improve the system, but most require doing that from a brand new state. Unironically though, we could just switch to air pressure, downsize, and use animal lard for grease, with vegetable and legume oil for lubrication... just an idea.
Some things about the difference between European cars and American cars that I am familiar with, all have to do with safety standards and legal challenges. Before I say that, I'll reiterate that I'm not familiar with their fuel standards. It's possible that they have more stringent laws about the toxicity of their gasoline and diesel. It's also possible that they use more ethanol. That said, even if their laws call for much stricter regulations, oil changes still need regular intervals for proper engine function over the lifespan of the vehicle. First major difference is in sturdiness. The body types, frames, and suspension on European cars are flimsy compared to American cars. They're allowed to get away with much more in dropping weight, at the expense of safety. My assumption is that this is because of the way their legal system works. In America you can sue anyone for anything. That's not how it works in Europe, and my guess is there's a fundamental difference to their "buyer beware" statutes. I don't know this for sure, but I've heard stories about it. My experience with the difference really hit home while I was buying my A123 battery pack. The Green Car Company I bought it from had a Smartcar in the lobby. They were brand new at the time, and not much was known about them. The body on the door was removed for the display to show what needed to be done to make them road safe in America. There was heavy beams installed to reinforce. On the sticker it showed the fuel economy, and it was about 40 mpg. There weren't engine upgrades to compensate for the weight difference, so they essentially added 1000 pounds on an engine built to handle 800 pounds. The European version got 70ish mpg from what the mechanic told me, but to comply with American road safety standards, the fuel economy was almost cut in half. This also puts a massive strain on engine wear, and things like oil changes are doubled or tripled in some cases. Tire wear is also a much bigger problem. Beefier tires means heavier wheels, more weight means beefier suspension, etc. This is a general rule of thumb in the fundamental difference between European cars and American cars. Their cars are flimsy, while American cars are stout. Given the general perception of Chinese manufacturing practices, I'm sure Chinese vehicles are even flimsier than European. Smaller engines, lighter cars, less safety all equate to less strain overall. I'm not surprised that they're able to go longer between oil changes, but never changing oil is just plain stupid. One of the things that my friend and I did while racing in the 90s was to evaluate oil quality after oil changes and carburetor rebuilds. Two things we did very often. Plus we were on a military base where that type of equipment was readily available. You can do this now by sending the sample after an oil change to a specialist technician. Some places even do it for free. Just Google "where to get an oil analysis." I'm sure there's dozens of places that are near you if you want ironclad scientific proof of what I've said here. The test will confirm that you have done your oil change at the correct interval, you were too early, or you went too long. Seriously, this guy telling you "they laugh at us" is a fool, and knows nothing about cars, engines, or motor oil. There's a lot of that kind of unbridled arrogance in hell, and in reality, he and all his European friends are just laughing at themselves for how truly ignorant they are. It's frustrating that people listen to their opinions at all, but that's the world of today: "sell yourself as confident no matter how ignorant you are." Don't be fooled by confidence. You called my "bluff" when there was no bluff. Do that with everyone who makes simplistic decisions about vastly complex subjects. There's a reason they're laughing, and that's generally due to insecurity displayed as false confidence or nervousness. I'd like to see your friend and his family make a statement like that in front of me an Jesse James having a conversation. Then you'll see a real laugh, and the funniest part is that your friend would be utterly clueless about why he's being laughed at... but he'd certainly feel the inadequacy and turn bright red from embarrassment.