Group II vs. Group IV oils?

Been doing some research into synthetic oils and am looking for a little feedback. Anyone know enough about oil to discuss the advantages of going to a full Group IV oil (truly synthetic) over a Group III (hydrocracked from a petroleum base-not truly synthetic) despite the significant additional cost? Any suggestion about good oils to go with and where to purchase? My inclination is to go with a full Group IV because I'm pointlessly anal about this kind of stuff, but I'm having a hard time finding out which oils are actual Group IV due to the massive amount of marketing hype around synthetic oils. If it matters, I'll probably continue to change oil around 5-7k miles to reduce any potential warranty problems, as my Mazdaspeed3 is only about 11k old. Thanks!

My 58 Pontiac is still on the original engine running dino-juice and no oil filter.

I know new cars are built to much tighter tolerances but you need to relax and stop over-thinking things.

CHANGING the oil regularly is probably far more important than the type of oil used.

Shawn

Castrol Syntec 0W30 is one of the few easy to find full group IV oils out there. I've seen it at walmart...

It has to be the 0W30 as the other grades are III's.

The bottle will say "Made in Germany" on it.

Google "Bob is the oil guy" for too much oil information.

Castrol also has an SLX line that is all Type IV $7.88 at our parts department...

Wally worlds gallon of Mobil1 is great.

As you have probably found, GIVs are hard to find in the USA. This seems to be largely due to the rather generous way that companies are allowed to label oils here, making GIII and GIV oils eligible for the "synthetic" moniker. Functionally, from what I've been able to find, these have been coming closer and closer to each other in capabilities. Some, like Shell's Rotella T Synthetic, use a very high quality base stock (XVHI, if I recall, but that's from memory) that is quite close to GIV in uniformity and quality.

If you insist on GIV, you're mostly going to be looking at boutique or Euro oils that will not be widely available. Look for German oils labeled "Vollsythetische". I'm pretty comfortable using GIIIs these days, even in turbo applications. If you're still concerned with GIII, look for things like the European ACEA certifications that are somewhat more rigorous than US standards.

You've got to grasp or at least accept the notion that enough is enough. Yes, a Group IV oil is a superior oil. Better flow, better lubricity, thermally more stable, etc.

BUT, people are regularly getting hundreds of thousands of miles out of their engines with regular oils. Just how long do you really need that engine to last?

fwiw, i run motorcraft synth blend in my MS3, no problems so far, and it doesn't burn off like the M1's do. YMMV