Gotcha, Drew. So the purpose of the *octane* is still to get higher compression. Avgas tends to have a higher octane because of the requirement to stop the valves from wearing? True?
@Rob. It would be quite simple. If the oil companies genuinely believed that there was a benefit, the could take a statistically significant sample of cars, and run some controlled tests that show a suitable improvement.
The fact that they don't, and couch their claims in marketing vagueness while relying on people to project their own desires speaks (in my opinion) volumes.
What *I* think it shows is that they *have* run the tests, and the know full bloody well that the improvements are nothing like what people want to think they are, so the simply don't publish them, CF 'Healthy' food, and , sadly, a lot of drug trials.
Your mileage may vary, and I'm doing this in good faith, so no insult or offence is intended to anyone. If anyone wants to discuss the concepts involved over copious beer, I'm happy to pay my share
C