Modern Vespa

Does really low octane gas produce knocking?

It can cause pinking, like a metallic pinging noise, but you know all these things can be ironed out with timing, jetting etc. However, I stick to premium fuel for both my scoots mainly as they survive a bit longer in the tank and doesnt go off so quick, both of which aren't over tuned etc. But I also appreciate you cant always find garages selling premium. So i guess to your answer, yes and no depending on your setup. I had a dr177 which pinked on low ocatane until changed timing by 2 degrees. The smallframe never liked low octane, but probably could have been adjusted to take it fine, however, too much bother for what its worth.

As a precaution against pinking and staleness I only use the non-ethanol "recreational" stuff, which in my area is always 91 or 93. The extra cost is pretty trivial given that I probably only run through 100 gallons a year.

Yes agree , geared Vespas you don't worry about cost of fuel versus MPG imo. It's about keeping engine happy , running effectively and e10 petrol has a very short tank life . Of course we only got e5 in uk as option , but it's far better to run at about 50p more per gallon. My small frame tank will only hold just over a gallon , 5 litres

91 for me. In my wildly unscientific thinkings, not many people splurge for 93 so it sits and goes stale before you pump it. 91 seems better in my experience

Ive had fuel go stale after 4 weeks when weather was hot. Ive also been told by local motorcycle garage theyve had guys going in with their with assumed motorcycle faults only to find fuel has turned after 3 weeks. Bare in mind, this isnt always the fuels fault, sometimes the garages have had it sitting in their tanks for months before hand. Find a good garage where you know the fuel quality is always consistent and stick by it. In the UK Shell generally has decent fuel.

One of the benefits in living in an area where we have lots of lakes and thus a lot of boats is that non-ethanol fuel is widely available. The boaters don't want to touch ethanol.

Same here - non ethanol unless I know I'm going to burn the whole tank....

just keep in mind that any USA posters are posting (R+M)/2 numbers not RON.

as with many things, we refuse to use the world standard for measurement on this.

Firstly.. what are you considering as LOW?

I use 98, or e85 (106?), but love the smell of AvGas if i can get it

AV gas is leaded. Watch those fumes

Here in Europe, only 98, which is E5. The regular 95 is normally E10.

Says the guy riding a 2/-

BTW: I've pumped a million or so litres of Leaded petrol... no worries that I can remember about

Ohh... in my race car (1980 KP60 Toyota Starlet, with Group A 4K Motor) i used to run AvGas, with Octane Booster, Toluene & a bit of 2/- oil!

BTW: it was the OG "Speedy"