2017 AMC 10B Problem 12

Elmer's new car gives 50\% better fuel efficiency. However, the new car uses diesel fuel, which is 20\% more expensive per liter than the gasoline the old car used. By what percent will Elmer save money if he uses his new car instead of his old car for a long trip?

\textbf{(A) } 20\% \qquad \textbf{(B) } 26\tfrac23\% \qquad \textbf{(C) } 27\tfrac79\% \qquad \textbf{(D) } 33\tfrac13\% \qquad \textbf{(E) } 66\tfrac23\%

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.