I know they have pretty small gas tanks, but a motorcycle is considerably smaller/lighter than an automobile, so I guess its all relative.
The reason I’m curious is because ads for motorcycles don’t seem to tout their gas mileage, its always with vehicles of the four-wheeled persuasion. How often does a motorcyclist have to fill up at the gas station? I almost never see them there.
Depends on the engine configuration, displacement and riding style. My EX250 (parallel twin, 250cc) gets about 60mpg on the street & about 45-50 on the track. My ZX6R (inline 4, 600cc) gets about 45-50 on the street and less than 30 on the track. The RC-51 (V-twin, 1000cc) gets about 30mpg on the street. On average, motorcycles probably get about 40mpg if ridden normally. They tend to have tanks in the 4-6 gallon range for sport bikes and about 7-7.5 for some of the larger Touring bikes.
Wow, my Geo meets or exceeds most of those figures 
I have a Honda Pacific Coast and I consistently get 50mpg. My tank is 4.2 gallons so I stop for gas every two to three days. When I get gas it doesn’t take me but a minute or two and I’m out of there, much less than when I’m in my car, where even if I’m done pumping I’m checking oil, cleaning windows, throwing away coffee cups, etc. Maybe that’s why you don’t see many there. Less bikes than cars, and when bikes are there, they don’t stay very long.
My Yamaha XJ600 Seca II gets between 50 and 55 mpg, and I ride it at about 75 mph (5,500 rpm). I can make two round-trips to work on about 3.4 gallons. My tank holds 4.5 gallons.
The Royal Enfield “Bullet” is a 500cc thumper that gets about 70 mpg.
skaterboarder87: Yeah, but just try lane-splitting in your Geo! 
Bikes used to get much greater mileage but then they were nothing like as powerful.
Something like an Triumph Bonneville could get up to 60mpg, but a bike of similar capacity would have maybe twice as much power and get around 40mpg.
Couple of things are responsible, not just the change in power output, one is that the power is more easily available, the Bonneville could lope along at a fair old lick but it took a certain amount of winding up to get to that speed, and really although the engine was rated at around 40bhp, the reality was that if you tried to use that power regularly, the engine could blow up, it was really a 25bhp engine that had been pushed somewhat.
If you take the modern version of the Triumph Bonnevile, the 800cc machine delivers 60bhp very reliably, and can do it without stressing the engine, it is also far, far smoother running than its ancestor due to balancer shafts, it is more torquey, but the price is that you only get 40mpg.
The modern Bonneville accelarates far better, and as any physics student knows, maintaining a particular speed is not what costs most, its the rate at which you get to that speed that does the damage.
I think that the Honda CB500 is a great bike, simple to maintain, capable of 110mph, handles well, and yet it can still give you 60mpg.
I ride 2 strokes that are not as efficient. My RZ 350’s are only good for 25-30 mpg as I ride. It has a “smallish” tank and you stop every 120 miles or so, which means about every hour and a half.
My 4 stroke singles get about 45 (Suzuki) and 50 (Honda) pretty consistantly. I picked up a Kawasaki twin and expect the same, but haven’t checked it yet. (I am so lame! I have ridden it a total of 32 miles since I got it almost a year ago!)
I think the reason ads for bikes don’t focus on milage is similar to the reasons Chinese food places don’t advertise about eating with chopsticks. It is really not a main part in the decision for purchase.
Fagjunk Theology: Not just for sodomite propagandists anymore.
I gotta tell ya, though: With gas prices still up around $1.70/gallon in California, good mileage is a godsend. If HYKS were to start advertising mileage (at least on “commuter” models like mine or the CB750), I think there would be a lot more people riding.
The reason is that motorcycles are nowhere near cars in aerodynamics.
My Moto Guzzi 1000S gets a bit over 400kms on a 20 litre tank.
As stated above, the issue of mileage is not really a main part of the purchase decision. Consider that a small car is often cheaper, gets about the same mileage and keeps you dry in the rain and you’ve got a good indication that there are other reasons for choosing a motorcycle.
It is accepted wisdom among motorcycle journalists (of which I was one for a while) that motorcycles are a “lifestyle” decision rather than a practical one for most people. I’d suspect that the motorcycle companies thought so too.
True enough. But take Southern California, for example. Gas prices are higher here than they are in most places, so the excellent gas mileage is a definite plus. Also, “lane splitting” is legal here. That means that you don’t have to wait in tailbacks. A new “commuter” bike costs around US$5,000, so after a few years it doesn’t really make sense to have complete coverage on it. My liability-only coverage is only $75/year. Many places allow motorcycles to park free of charge. Finding street parking is very easy, since you just back the bike into a metre-wide opening. Relatively high power-to-weight rations mean that it’s easy to accellerate into traffic and maintain safe seperation between vehicles. Being single, I can fit all the groceries I need in a backpack. For larger loads I can bungee things to the rack and rear part of the seat. And as much as I dislike excessive sun, I have to admit that it allows me to ride often. The “fun factor” is the biggest thing, but motorcycles are more practical than many people realise.
Going roughly by the figures posted in this thread (and to give a somewhat definitive answer to the OP), bikes get about 40-60 mpg; some more, some less. But that’s a pretty good figure.
The Royal Enfield “Bullet” I mentioned earlier is basically the same bike they’ve been building since 1955. As such, its power is minimal compared with modern bikes. Its absolute top speed in stock trim is 75 mph. That’s not really fast enough for the freeways around here. On the other hand, it’s cheap (about $4,000) and it gets 70 mpg. It would be a good bike for around town, but not so good on the freeway.
Bikes AVERAGE ABOUT 40-50miles/gallon. You tend to ride bikes very inefficiently (well, I do!!)…Grab some throttle, hard on the brakes as some cage is blocking the road, back on the gas…
You also go through tires much faster than with a car.
Gas is about $2/gallon here, so I ride the bikes as much as possible.