[freebeard]

Low Octane fuel
Inspired by a thread about hot air instead of cold when for eco driving. A friend claimed he got a little extra distance/tank when running low Octane fuel. So the reaction might happen a bit faster getting more power from each stroke. Driving very economical, detonation might not be risky. Now, I have no idea weather it makes a positive effect. Also, high revs on a hot summer day might be a very bad idea on a moderne engine with higher octane requirements.

Low oil
Getting oil at minimum or even lower, will in some cases lower friction from crankshaft dipping in oil pan.
A side effect is also that the oil heats up faster.
Oil temp monitoring might be a good idea if also running on low viscosity, as low viscosity oil draw more heat.

Doesn't apply to the VW Beetle.

Clear Premium is equivalent to the fuel that was available in the 1970s. Your low octane mixes will contain ethanol, which lower the mileage and attacks fuel lines.

More oil (a 14-quart dry sump?) is better when you rely on it for cooling.