Honda
There used to be a time when the term "mini bike" would mean a simple thing. A small motorcycle that featured a small lawn-mower-derived engine, bolted onto a simple frame and transmission. They were cheap to buy, easy to maintain, and a lot of fun to ride. Fast forward to today, and the burgeoning popularity of the mini bike has given rise to multiple categories of these interesting little machines. While legacy brands like Honda, Kawasaki, and Benelli are mostly known for their reasonably powerful, street-legal mini bikes like the Honda Grom (and its competitors), there are a number of smaller manufacturers that have created an entirely fresh category of entry-level mini bikes.
These machines — usually sold by companies like FRP, Massimo, Mototec, and Coleman — are smaller, produce less power than those from more mainstream brands, and aren't usually street legal in several states. Despite the major differences between these two mini bike categories, a few things haven't changed: These machines continue to be tiny, lightweight, and don't demand anything exotic when it comes to fuel quality. This is mostly because engines used on mini bikes are small-capacity, low-compression units that run perfectly fine on regular unleaded (87-octane) gasoline.
So, irrespective of whether you own a Honda Grom, a Kawasaki Z125 Pro, or a mini bike from FRP, they will run just fine if you tank them up with regular 87 octane fuel. In fact, a quick glance at the user manuals of these bikes will also confirm that they do not require premium, high-octane fuel.
Why your mini bike doesn't need high octane gas
Kawasaki
Despite the huge variety and types of mini bikes sold today, they are, at the end of the day, motorcycles that use simple, low-power engines. High-octane gasoline, on the other hand, is usually recommended for high-compression engines, typically found on supercars, sports bikes, and performance cars. In these powerful engines, the air-fuel mixture is squeezed harder before ignition compared to mini bikes with small engines. Another reason manufacturers of these high-performance vehicles typically recommend using high-octane fuel is its capability to resist a phenomenon called engine knock, especially under heavy load.
Mini bike engines simply don't generate the kind of cylinder pressures that would require them to use premium fuel. If that wasn't all, on vehicles that need regular octane fuel, using high-octane gas doesn't offer any performance improvement under normal conditions. It won't produce more power, improve the mileage, nor would it increase the engine's life. So, whether you have a premium mini bike from Honda, Kawasaki, or one of the more affordable ones from Coleman, Massimo, or MotoTec, the recommended fuel is nearly always the same: 87-octane regular unleaded gasoline.
Now, there is no inherent harm in tanking up your mini bike with high-octane fuel. But do keep in mind that by doing it, you'd just be paying more money for no tangible performance or fuel efficiency benefits.
