>>2067716Bikes are weird, they seem like they shoud be more efficient but their aero is shit, and their engines tend to be so high-strung that very few actually are even at lower speeds.
You gotta consider that something like Honda Hornet is not equivalent to a baisic Honda Civic, it's equivalent to a tuned Civic with ITBs, angry cams, straight pipe exhaust and rev limiter at over 9000, and it needs to rev that high because there is no low end in the engine anymore, a very good way to guzzle fuel. Meanwhile, say, BMW R1200 is kinda like a BMW 5-series with a 4-liter V8, an understressed engine that doesn't need to rev much but also a wildly oversized one, not a paragon of efficiency either. Both of them will get around 6 l/100 km, which is indeed better than their equivalent cars but not spectacular in the grand scheme. And both of them are also stupidly fast by car standards.
Honda does make a bike that's built like a car, the NC. It's got a literal half of a Honda Fit engine with exactly half the power of one, it's torquey and understressed but not particularly powerful, it goes fast enough but not too fast, and it gets 3 l/100 km. That might be the limit for a highway-capable bike. A moped that never goes above 50 might get better mileage but most developed countries aren't accomodating to those kinds of vehicles anymore.
The real fuel saver in bikes, though, is not having to stand in traffic jams. But that only works in car-centric societies, because when everyone is on a bike, oh they jam each other just fine, take a trip to Thailand to witness. Also applies to bicycles, I had a pleasure to stand in (rather, waddle through) a real all-bicycle traffic jam in Amsterdam, would not recommend.
