Modern Buddy

The Buddy 170i owners manual does not mention octane.

The compression ratio is 10.5:1 so midgrade is fine but you can use premium if you want.

Most use 87 octane with no ill effects.

There is no mention of octane in the Hooligan 170i owners manual but the shop manual calls for 91 octane. Since I started using 91 octane the Hooligan runs better.

I don't know about the manuals for the 170i family (Buddy & Hooligan), but in the older PGO 50/125/150 manual, the octane figures were given using the RON method, not the R+M/2 method common in the USA. Thus, the higher RON value was met by 87 or 89 regular here.

This really means the bike will run to spec on US regular. However, lotsa folks believe / perceive that their bike runs better on mid-grade or premium. I can't tell any difference in my 150, but use what feels right for you. Short answer - regular won't hurt. Although I'm betting that Taiwanese gas ain't got the miserable ethanol that we do.

This is what Genuine Scooters said on this subject -

Here are the recommended minimum octane’s for our legacy and current models. These octane figures are based on the engine compression ratio and having electronic ignition with a built in advance.

Buddy 50, Roughhouse 50, Black Cat 50, and Rattler 50: regular 87 octane

Rattler 110: regular 87 octane

Buddy 125: mid 89 octane

Buddy 150 and Blur 150: mid 89 octane

Buddy 170 and Hooligan 170: high 91 or 93 octane

Blur 220: high 91 or 93 octane

Stella 150 2T: mid 89 octane

Stella 150 4T: mid 89 octane

Stella automatic: mid 89 octane

For the Buddy 125 model: although the recommended octane is 89, we have had many reports from dealers and consumers that have been running regular 87 with no issues and several thousands of miles.

Best,
Genuine Scooters

(this was extracted from this previous thread - viewtopic.php?t=21671&highlight=octane+requirements )