MPG with Shell V Power and BP Optimum

[Dan_FR]

98 will have no effect at all on the PCV system or the valves as no fuel passes over them. Fuel octane rating relates to its resistance to knock (pre-ignition), not the potential energy within the fuel and how far you will be able to go on a gallon

Too many variables over a tank of fuel to draw a conclusion from 2 tanks worth anyway. You won't notice much difference on a standard car (few hp) but it's a lot more important once mapped and making use of more timing advance

[ReflexRob]

Yeah I agree but what about the cleanliness of the burn? Unburned particles will get recirculated through the PCV system won't they? Otherwise, what we are being told about 95 not being great for our engines can't be true.