Disadvantages of the Two-stroke

You can now see that two-stroke engines have two important advantages over four-stroke engines: They are simpler and lighter, and they produce about twice as much power. So why do cars and trucks use four-stroke engines? There are four main reasons:

Two-stroke engines don't last nearly as long as four-stroke engines. The lack of a dedicated lubrication system means that the parts of a two-stroke engine wear a lot faster.
Two-stroke oil is expensive, and you need about 4 ounces of it per gallon ofgas. You would burn about a gallon of oil every 1,000 miles if you used a two-stroke engine in a car.
Two-stroke engines do not use fuel efficiently, so you would get fewer miles per gallon.
Two-stroke engines produce a lot of pollution -- so much, in fact, that it is likely that you won't see them around too much longer. Thepollutioncomes from two sources. The first is the combustion of the oil. The oil makes all two-stroke engines smoky to some extent, and a badly worn two-stroke engine can emit huge clouds of oily smoke. The second reason is less obvious but can be seen in the following figure:

Each time a new charge of air/fuel is loaded into the combustion chamber, part of itleaks outthrough the exhaust port. That's why you see a sheen of oil around any two-stroke boat motor. The leaking hydrocarbons from the fresh fuel combined with the leaking oil is a real mess for the environment.

These disadvantages mean that two-stroke engines are used only in applications where the motor is not used very often and a fantastic power-to-weight ratio is important.

In the meantime, manufacturers have been working to shrink and lighten four-stroke engines, and you can see that research coming to market in a variety of new marine and lawn-care products.

For more information on two-stroke engines and related topics, check out the links below.

How Two-stroke Engines Work

Disadvantages of the Two-stroke

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