Diesels are not very common in the U.S., but they are popular in Europe in the same way that diesel cars are more popular in Europe.

Two problems with diesels: they stink and the fuel is hard to get. Many people find the smell of running glow engines to be somewhat pleasant and unoffensive, but the same can't be said about diesels. Unfortunately, you can't run model diesel engines on diesel you buy at a gas station or truck stop. Model diesel fuel has a fairly high percentage of ether mixed with it to aid ignition, and ether (due to its use in illicit drug making) is a controlled substance and hard to get. You essentially need to buy it from one of only a few sources in the U.S. where it'll cost you over $20/gallon.