Hi, Gunny
Well, I've only seen one way to stir things up faster than ask "what kind of oil and how often to change it?" in an automotive forum, and that was when I was kid in San Diego and watched a coupla drunken sailors stumble into a bar full of Marines and holler out, "You guyshhh are all a bunch of wimpshhhhh!" It got exciting FAST! And that's about what you'll see in your answers here (or other auto forums!)
We all have our opinions, but that's all they are. I've challenged people over the years to "show me your numbers" about why this or that is better, and nobody can...
So I'll give you MY opinion, based on the last million miles I've driven: pick your favorite brand of dino oil in the right weight and service grade (API, ILSAC), change it and your filter every 3000 miles (or use your book's recommendation for "severe" service), and report back in a quarter of a million miles if there's any oil-related problem!
People are going to tell you that's a waste of money. They're going to tell you this filter is better and that one's garbage, they're going to make it seem like your engine will probably just fall off its mounts if you don't use their brand of oil. It's almost all bunk! Clean oil's about the cheapest insurance you can buy for your car, and as long as your choice meets the mfrs recommendation, you're good!
Synthetics? Yeah, they seem to be "better" than dino oils. But how much better and at what cost? I've tried several of them, and I keep pretty detailed records of such stuff. Never have they proven to be cost effective for me. I live near Palm Springs, CA, and it's just a bit warm this time of year (111 deg F yesterday, should finish warmer today.) I'm currently running a "test" w/ Super-Tech synthetic (from Wally World--the cheapest one on the market. In the past I've "tested" Amsoil before there were really any others on the open market, Mobil 1, and Castrol Syntec) in two vehicles to see if anything's changed as far as cost effectiveness. So far, no joy. Where synthetics shine in my book is their ability to clean, and keep things clean, particularly if there's much varnish in an engine. Your "new" LLBean shouldn't have that problem!
"True" synthetics vs "that's not a true" synthetic? Synthetic blends? You pays your money and you makes your choices. There's plenty of argument about what IS or IS NOT synthetic. Ever get in those Ford vs Chevy arguments at lunch in high school? Same concept. All the big oil companies have been butting heads, mostly in court, about the definition of "synthetic" and basically, for US purposes, it's marketing that wins out. You REALLY don't know any more about what you're getting than what it says on the jug.
When to do the switchover to a synthetic? Whenever you feel like it. Several cars today come from the factory w/ Mobil 1 from the get go. Mobil says the "run it x number of miles to break in" is an urban myth. Others swear you should put 3-6k miles on dino oil first. You should have that kind of mileage already? If so, the question's moot.
The only "bad" thing about a switchover is if you have a hi-mileage car that's not leaking cuz the seals are being "helped" by a build up of goo over the years: it's likely a synthetic will clean things out well enough a "hidden" leak may surface. But today's synthetics by and of themselves don't CAUSE leaks.
Extended drain intervals w/ synthetics? You'll see all kinds of claims. If your car's under warranty, they're all bunk, cuz you've gotta follow the warranty instructions or void it. I'm sure it's quite likely you CAN run fairly long OCIs (oil change intervals) w/ the kind of driving you've proposed, but it's usually suggested you do oil analysis to know for sure. So you can change your oil at 3000 miles w/ dino oil for $20, and know for the next 3000 you're good. Or you can spend $20-$30 at 3000 for an oil analysis on your far more expensive synthetic oil that might say "change right this minute" or "come back in 3000 miles and we'll do this again." See any economy in that? You're not saving any money, just making different choices on how to spend about the same amount!
So, those are MY opinions, and we'll see if I've done my part to get things flying... but in the long run, do what makes YOU comfortable at the spending level you find acceptable, and you should be just fine REGARDLESS of what you choose!
Rick