Here's a missed point in any DIY function (i.e., oil changes and such) when a vehicle is under warranty. DOCUMENTATION. Plain and simple.
Here's an example from a long-ago (late 1990s thread in the old Usenet Chrysler BBS). A man purchased a new Dodge minivan from a dealer in CA. He wanted to keep it well and went to the dealership's service manager to see what brand/type of oil they used in their service department. He stated his intention of doing the oil changes himself, which got no ill remarks from the service manager. The man used an oil filter which was stated to "meet or exceed factory . . . ". So he did the oil changes (after the first free one) himself. A year or so later, his engine cratered. "Oill sludge" was the determination. Which typically equated to "lack of maintenance", so the warranty claim was denied, upon inspection of the failed engine.
The owner was naturally not pleased. He maintained that he'd done the oil changes at the mileage states in the owner's manual. Claim still denied. Reason? LACK OF DOCUMENTATION of what he'd done. No sales receipts for the oil or filter, for example. They might not have had a mileage figure attached to them, but they would have a date. A date which might have been then related to a mileage amount.
At that time, most oil filters had a flap on the box where mileage and dates could be written. Ad that to a sales receipt, and that would have been on level of documentation which could be presented, if needed. By the same token, the old oil change stickers which service stations used to stick to the door frames would similarly be documentation (having mileage and dates), too.
Turning things around . . . if YOU were the manufacturer and a dealer was requesting YOU to pry for a warranty repair/replacement of an engine which appeared to have failed from lack of maintenance, would YOU want to see documentation of performance of the prescribed maintenance, too?
I'm not sure about the Amsoil issues mentioned, but it seems to me that Amsoil used to claim that you could extend the maintenance intervals with their motor oils. Only thing would be that the brand/type of oil is not mentioned, just that it's done at a particular time/mileage interval. BTAIM.
As for oil change intervals, there used to be TWO maintenance schedules. "Normal", which has the longest time/mileage oil change intervals and the "Severe Use" schedule, which has much shorter maintenance intervals, due to the fact those vehicles would see either HD use or "trips less than 10 miles/trip, frequently". Problem is that what many might consider as "normal use" is actually more like the "severe use" actual vehicle use! Many perceive that as long as the coolant temp gets "hot" each time the vehicle is started, that's "normal use". But it usually takes about 10 miles of highway driving for the engine OIL temp to approach engine coolant temp. SAME with the ATF temps, too. So unless the motor oil gets hot and stays hot for a good while, the moisture from crankcase condensate does not get "cooked out". As a side note, daily use of my '80 Newport 360, in cooler/cold weather would still result in a milky accumulation at the top of the dipstick and a clogged pcv line to the carb . . . with no loss of coolant level in the radiator.
Back when the Dodge van's owner had his engine problem, with no documentation of maintenance, there were developing many issues with "oil sludge monster" engines from USA manufacturers. Not just Chrysler, either! Which would relate to the brand of motor oil, with some being worse than others, although meeting the same API specs.
Back in the early 2000s, we did a complete engine replacement on a Cadillac NorthStar V-8, just before it went out of the manufacturer's powertrain warranty. The issue? Oil consumption. Documentation, our dealership had done all of the oil changes since new. Which meant we had a pile of "documentation". After doing the GM-prescribed oil consumption test, which we also administered, approval was granted to do the engine replacement. Had the oil changes been done somewhere else (outside of the dealership network), the replacement might not have been approved as readily.
There are NO issues with people changing their own oil and such, might even be better than it would be otherwise, if somebody else did it. But as long as the vehicle is in factory or extended warranty periods (time and miles), that dealership oil change CAN be the best way to do things, by observation. Plus not having to deal with the removed oil/filter recycling operations. Some customers used to bring their own oil, let us sell the OEM foil filter, and let us to the labor. For a reduced total charge. No problems there, either. But as oil specs have changed on newer vehicles, the most bullet-proof way to do it is to let the dealer do that stuff.
Remember when Mercedes had their engine problems in the 1990s? Many claims from customers were denied due to "lack of documentation" of oil changes. But if the dealerships did the oil changes (with documentation), those claims were paid, as long as the maintenance interval was "to spec". Even if the dealership used a less-expensive motor oil than most European owners might have used. It was noted that most European owners would be more likely to use synthetic motor oil, whereas many USA owners would use the least expensive oils (including, as it was discovered, many Mercedes dealers).
During that same time, BMW had engines which required a 10W-60 motor oil. They wisely went to a "bumper-to-bumper, maintenance included" factory warranty. Which meant that the dealers stocked the correct Castrol-sourced BMW-spec motor oils. As I recall, about the only place to get the 10W-60 Castrol was at AutoZone or the BMW dealers. Their engines which didn't require the 10W-60 oils used something more readily-available, so no oil-related issues with that engine family. So, BMW side-stepped a huge amount of negative press for their products with their expanded maintenance-included factory warranty.
Thanks for your time. Just some thoughts and observations,
CBODY67
