John...I'm wrong but you're too lazy to prove it? Well, that sure sums up the experience...opinionated in a non-informational manner :
Unclemick...the 'filters only' change is one of those 50 year old bits...before oil additives and detergents it was common to change just the filter and add oil. Engine tolerances were so poor that you needed some gum to help 'seal up the works' and engines, regardless of what and how much of the contemporary fluids you put in them rarely made it past 50 or 60,000 miles without a major overhaul.
Should you change filters only with one of todays engines, the gum buildup would initially cause drag on the finely machined parts and eventually cause friction, heat, and engine failure.
Basically you have three things that make up engine oil and two influences on those things.
Your oil has a basic lubricating ability in its film strength and viscosity...viscosity is the fundamental 'thickness' of the oil while film strength says how thin a 'film' of the oil will still provide a certain level of lubrication between two facing parts under a particular level of pressure/tension. Over time and with the influences of heat and the introduction of combustion byproducts, the viscosity and film strength of the oil wanes. Consumer reports tested a variety of oils in the worst possible conditions...new york city taxis. They showed that all of the oils still showed a very good level of viscosity and film strength after 5000 miles, and at the manufacturers recommended change point of 7500 miles, they were still meeting the need quite well. Synthetic oils offer greater film strength and longer lasting stable viscosity, however the 'additive package' in them usually runs out long before the base oil itself breaks down.
Your additive package consists of a detergent to break down the gum that forms when the base oil starts failing, and elements that neutralize combustion byproducts. In a newer, cleaner burning engine these will last longer; conversely, in older motors that have some 'blow by', they wont last as long. When the additives are gone, the oil breaks down quickly. Most engine oil additive packages will easily last 7500-10000 miles in a new engine, and 5000-7500 miles in the ones that are older but not smoking badly. Additive packages are effected by heat, high pressure, combustion byproducts, and excessive short run periods. If your engine oil comes up to a peak temperature, some byproducts become vapor and are recycled through the engine cylinders during the combustion process. A 3 mile trip to the store causes startup byproducts to enter the oil, but the oil never comes up to a high enough temp to vaporize them. So they sit in the oil and force the additive package to neutralize them. This results in early consumption of the additive package, resulting in early oil breakdown.
Modern oil includes stabilizers, and an unstarted vehicle creates no byproducts for the additive package to neutralize. The stabilizers are more than adequate to maintain the base oils stability for more than a year of non-use in an engine. However its good to get a 10-15 mile/minute run on the engine to maintain top cylinder and valve lubrication, as long as that run is long enough for the oil to come up to a temperature high enough to burn off the startup combustion byproducts.
Applications involving diesel, turbos, and high compression engines create more byproducts, the additive package gets used up quicker, and they also involve higher pressures and temperatures, which stress the base oils viscosity and film strength. Hence these applications often require oil changes in the 3000-5000 range.
Drawing from this, an average non-turbo, ordinary compression level (under 9:1), gasoline powered engine of modern manufacture that has been reasonably well maintained and is under 150,000 miles does not require an oil change any more frequently than 6000-7500 miles and/or a year of service, whichever comes first. Which is why manufacturers specify those limits in the book; they're not paying for the oil changes, so why would they tell you to do something that would shorten the life of the vehicle?
Synthetic oils are essentially a waste of money. The additive package will expire long before the oil does, and you have to change the oil at that point anyway. And although it has a higher film strength and more resistance to breakdown of the base lubricant, the oil doesnt offer any significant lubricating benefits during its lifetime than a quality non-synthetic oil does.
Oil filter quality also does matter. An oil filter basically consists of a base plate, a metal can, a filter element and a bypass valve that allows oil to flow when its too thick to pass through the filter element, when the filter element is clogged, or when the oil flow demands of the engine exceed that of the filters flow rate. Some filters use paper elements, some plastic. Some use a metal spring and metal bypass valve assembly, some a plastic valve and a cheap piece of flexible metal for a bypass. The filter assembly is glued to the base and valve, and a retainer is applied to the filter material to hold it in place while the glue dries. In some cheap filters, a smaller area paper filter cheaply glued to the base plate and wrapped in twine is used, while an expensive filter will use a synthetic plastic element with a more sophisticated wrap. All is well with your filter unless the bypass valve fails, the filter is not securely glued during manufacture to the base plate, or the filter retention product (the string in a cheap filter) comes off. This can cause a loss of oil flow, unfiltered oil to pass into the engine on a sustained basis, or actual pieces of the filter to break off and be distributed through the engine. Which is why you want to avoid cheap no-name filters, and many common manufacturers like Fram who make very cheaply made filters. Purolator and motorcraft, among others, have gotten good marks.
So Johnny...what does your superior intellect tell you I got wrong?
Al - Maintenance on some cars requires more work. In particular, a lot of german cars I've worked on were not only not engineered to allow for easy maintenance, they appeared to have been specifically constructed to prohibit shade tree mechanics from having a good time with them. Japanese cars are (in my experience) no different really from your basic chevy with regards to maintenance. The only thing I've seen that makes much difference with them vs an old detroit iron engine are some slightly exotic items like spark plugs installed through the heads vs under them, or the mounting of a coil on top of each plug - something VW also does, but its very easy to remove the coils, and a long socket wrench makes the through-the-head plug removal and installation no more complex than an old chevy.
In other words, you're being ripped off. You bought an expensive car, they're going to charge you expensive maintenance. Car companies dont make jack on the car anymore; the big money is made between when you and the salesman agree on a price, and the 'finance guy' works you over for paint sealer, alarms, stereo upgrades, window etching, and the service guy gets you for 'factory maintenance'.
Tires are tires, but some manufacturers (in particular expensive and performance cars) specify higher speed rated tires (S and V are common). These tires are guaranteed to hold together at speeds between 120 and 150 mph. Many tire installers will not go against the manufacturers tire speed rating when installing a tire. I ran into this with my Infiniti, where high speed rated tires that cost 40% more were manufacturer specified. Even though I wasnt planning on exceeding 100mph in my car, most shops wouldnt install a lower speed rated michelin. So blame the car company again.
