Actually, most of the bearers of this surname Diesel in South America are of Hispanic origin, also bearing a Spanish first name. You are right that some people might be German, but as you can see, this surname Diesel is rare, not as popular as Johnson or Jones, making it highly unlikely that there may be some Diesels living in South America and in Asia. I'd say 97% of Diesel in United States and Canada are of German origin, and 90% of Diesels in Europe are living in Germany, making your idea even more unlikely. In the Philippines, there are a few people who bear this surname Diesel, and according to my research, they are Filipino of origin. Variants include Dies, Diez, Dienzo, Diezon, and Diezel, possibly a variant form of Filipino surname Dizon, of Chinese origin. These variants sound Spanish, but they are very rare Filipino surnames. The surname Dies and Diez are most popular in Spain than other places in the world, but that doesn't mean that the Filipinos that bear this same surname are consider Spanish.