Jerre,
As an accountant who worked for me in a tax office once put it, "My logic may be faulty, but you won't find errors in my math."
I won't argue there are many ways to "cook the books" regarding cost per mile with extended oil changes vs 3,000 mile intervals, but when the mfr specs 3,000 miles for warranty coverage regardless of the oil mfr's recommendations (as was the case at the time I did my unofficial tests, and is STILL the severe service recommendation from many in the US market) we're stuck comparing apples with apples. Like it or not, oranges won't work. (Remember how quickly Mobil 1 dropped their 25,000 mile recommendations when the auto mfrs wouldn't buy warranty claims?)
When someone can prove to me definitively that synthetics with extended change intervals will save me money, I'll listen. But in 25 years or so, all I've seen and heard is "they're better" without any numbers attached. When I looked at my own numbers, they didn't convince me. What would I like to see? Engine life including repairs of lube related components, fuel consumption, oil cost including changes, filters and between change consumption would all have to be factored in to attract my attention. In other words, TCO--total cost of operation. If TCO is less with synthetics, great. If not, I see no need to change. No "feel good" or "I sleep better" factor is included because they don't have a price.
At the time I tried Amsoil, extended change intervals of up to 25,000 miles were recommended (if one used Amsoil filters and/or a bypass system such as a Frantz or later incarnations combined with oil analysis.) Oil analysis was recommended at 5,000 mile intervals. Cost of oil analysis plus the extra oil and filter costs at the time ate up any savings from the extended change interval. Perhaps that's changed, but it wasn't the case when I worked up my numbers.
As for disposal, I've recycled every drop of oil I've ever changed since
1965 when I started changing oil, whether I was working in a shop or doing it at home. As has everyone I know who does their own oil changes. The improper disposal argument may be valid somewhere, but it holds no water for me.We could also possibly have life supporting stations on the moon. But neither is likely to happen with current technologies, mentalities and budgets combined. From what I understand, approximately 50% of a barrel of oil goes into fuel (gasoline and diesel primarily) and perhaps even more if we consider heating oil. The amount that becomes lubricating oil is rather low. The surest way to reduce foreign oil dependence is related to reducing our consumption of fuel. Period. Quit driving those gas guzzlers, America. Period, end of argument. I don't see changing our types of lubricating oils as doing anything significant. BTW, where do synthetic oils come from? Corn fields? Soybean fields? Peanut farms? Even if they did, there's a lot of diesel fuel burned up making the raw materials. Sooner or later, it loops back to petroleum. It's all part of the "no free lunch" idea.
Question: how many Europeans routinely put 30k miles a year or more on their cars like so many American commuters do? I don't know, but if their driving habits are anything like the Japanese, who routinely dispose of their cars with only 30k or so miles (because of stringent inspection requirements and the cost of complying therewith), why bother changing oil at all? It's not cost effective, so why bother? I'm sure more than a few people have known someone like the fellow I once ran into who'd run 100k miles on dino oil without ever changing it--he changed his filter every 5k miles and topped it up and off he went. I'd have hated to see the inside of his engine, but it was still going. So extended change intervals are moot if the cars aren't driven that many miles before being disposed of. Again, apples to apples, not oranges.
Just some thoughts and opinions. Nobody has to agree.
Rick