Is high octane fuel worth it in a Toyota Corolla Hybrid?

I was wondering if high octane petrol was worth the extra price. I asked two car oriented friends recently and they both said “absolutely - wouldn’t not use it”. Another friend said it has no effect except on high compression engines which modern cars are not.

Anyhow, I’ve been doing an experiment. I let my Toyota hybrid run very low on fuel and filled it with 98.

Here's what I see after a tank of Unleaded 91 fuel:

Here's what I'm seeing after a fair amount of a Premium 98 tank:

Normally I get 4.3 l/100 km. On high octane I’m getting 4.1 l/100 km. So it seems to make a small difference but not enough to justify an extra 20c per litre.

Here is where I fill up locally:

As is normal for a headline that is a question, the answer is no.

FreeDV with VK3SRC and VK3CKY

Just a little off air recording of some local stations talking with FreeDV RADEV1.

Joe VK3SRC asked about those "wings" (as he called them) on either side of the main carriers. He hypothosised that they were extra error correction signals. In fact they are an unwanted side-effect of the current RADEV1 code that will be removed in a future version.

To test this he used filtering in his transmitter to nicely remove them. You can see a "normal" signal at the bottom and his frequency limited signal above:

The resulting signal was perfectly decoded and has less wasted transmitter power.