Typical gas-powered leaf blowers use a 2-cycle engine. These in general are not efficient, and need oil combined with the gas to lubricate the motor. This oil is of course burned as part of the combustion, which generates a lot more pollutants than an efficient 4-cycle internal combustion engine (such as in your car).

These leaf blowers also don't have much of a muffler system (due to size / weight) and of course no exhaust gas recirculation or catalytic converter to further reduce emissions by-products.

Nit pick, apologies up front. Two stroke motors are actually more efficient than four stroke motors, they just emit a bunch of pollution due to the oil in the gasoline, which is a much dirtier combustion than gasoline.

A two stroke motor is considerably simpler than a four stroke, they often come in at around half the weight for an equivalent power output, and have less moving parts. This is why they are the default engine of choice for hand powered tools - almost no maintenance, very little warmup cycle, high power:weight ratio. The downside is dirty exhaust.

Modern two stroke dirt bikes have actually all started moving to fuel injection to help combat this. No premixed oil/gas, oil is injected at an optimal ratio given the load of the engine. Light cruise / idling, they run at 100:1, at heavy throttle they drop down to 50:1. Much more pleasant than something set to constantly run, via premixing, at 50:1 gas:oil.

Other note: large ocean freighters are two stroke engines: https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-Sulzer_RTA9...

There are different types of efficiency. I think you might be referring to power per weight, while the parent comment is talking about emissions per (unit of) power.

To dig further, you can also differentiate between peak and sustained power; MTBF, maintenance (and dollars of maintenance) per hour of operation, volume, overall environmental effect (due to lifespan and manufacturing), etc etc.

I am referring to both thermal efficiency, and power to fuel ratio. Meaning, for any given amount of work needed, a two stroke will produce more work for the same input of fuel as compared to an equivalent quality/design four stroke motor.

Your point is a good one though, but I think the common use case of the word efficiency, when talking about vehicles, if fuel required to produce a given amount of work (miles, horsepower, etc).

I actually was talking about thermal efficiency of two-stroke vs. 4-stroke, and believed that overall four-stroke does better.

Reading about just a little bit, this may not be the case... depending on what application you are talking about.

I would expect to be some differences between a 10-ton marine two-stroke on a ship vs. a 49cc two-stroke on a moped in terms of efficiency.

For some reason this confused me more than normal (just not the usual context I'm familiar with it in I suppose) - so just to be clear, you mean the same 'gas' that goes in your car right? Not that you can get, I don't know, propane leaf blowers or something?

They are noisy and smelly as hell, there was some going on just outside my window (not that I'd hired) recently, the operators wearing ear protection of course, but I was barely any further away. Do wish they'd use electric - can do it from a battery even these days. (And mitre saws etc. too, quite incredible.)

Yes, many of the gas leaf blowers use regular automotive gasoline, with a 50:1 mixture of oil added to the gasoline.

They do have electric leaf blowers, but those offer minutes of runtime instead of hours. So those might be suitable for a homeowner, but aren't very practical for professional lawn care use.

> They do have electric leaf blowers, but those offer minutes of runtime instead of hours

This confused me for a second, as the electric leaf blowers that came to my mind have 'infinite' runtime. I then realized you're referring to cordless electric leaf blowers.

I know they (the blowers) exist - I meant I wish they (the specific people operating beneath my window) would use them.

The 2-cycle vs 4-cycle engine distinction applies to gasoline engines used for a wide variety of applications.

Ah sure (mix with oil for 2 stroke right?) - it was just the US 'gas' terminology that threw me off. Somewhat used to hearing it for cars, but in this context my first thought was of pressurised cannisters of butane, propane, whatever strapped to the back of someone operating a leaf blower!