I've mixed leaded/unleaded and my oxy sensors live for years but now I just stick to VP-101 and mix w/91 for cruising and straight when racing. As far as ideal ratios, I agree run it at the track, jet up till it slows and there's your ratio on THAT day in that da which changes and another thing, this cruising in the 15's 16's bs with carbs and BIG duration cams with lots of overlap is NOT the answer like EFI which uses a tps to up pulse widths rates and injects fuel directly on to the intake valves.......... Two different worlds completely just like Dragula is finding out w/my carb and a HEMI and several others also. You want stellar mileage in a old muscle car then put a GEN-3 in it and enjoy the ride........