100 octan

No, no damage......probably.

But absolutely, positively NOTHING to be gained by doing so.

 

Although I am not familiar with that exact "racing" gas, I would be very wary. My previous racing days are behind me, but it 'useta' be that fuel specified as "racing" had lead additives in it for upper engine/valve lubrication. May not be the case for something as low as 100 octane, but you'd better look first. If I remember right, lead will smoke the cat converter rather quickly.

Umm... never mind I guess. A bit of looking online and this is pretty much an 'across the pond' thing. 100 octane there and 94 here?

An odd thing to call "racing" gas

 

According to some maintenance manuals, high octane can lead to hard starting issues in Gen2 Prius. However, to my knowledge nobody has ever reported seeing that problem.

Racing gas can be high energy content due to more aromatics - but there are other ways to get the octane such as ethanol. I would expect to see up to 10% better MPG over the USA Reformulated gasoline in my area. However, you do not live in my area, so I am not sure you will see too much difference.

 

I'm going to say that this will add at least +50hp. Use race oil in your Prius will add at least another +20hp. Cold air intake +10hp. Straight pipe +20hp. Paint your Prius red with racing stripes for another +10hp. Racing stickers +5hp. Add it all together 110+50+20+10+20+10+5= 234hp!!!!!.

...

The Prius engine has a compression ratio of about 8:1 (expansion ratio of about 13:1 due to Atkinson cycle). Therefore the cylinders never compress the fuel enough for the additional anti-knock properties of high-octane fuel to make any difference. You won't see better fuel economy or performance with this fuel. However it won't hurt the engine either.

 

i have read that higher octane makes the engine quieter.

 

And what other "interesting" things have you heard ??

Higher than what.....and quieter than what ??

While that is true in some cases, most of it is the placebo effect.