Do you mean (R+M)/2 ? ----- Original Message ----- From: "Rog & Jan van Hoy" <vanhilla@xxxxxxxxxxxx> To: <mailing-list@xxxxxxxxxxxxxxxx> Sent: Saturday, April 26, 2003 12:55 PM Subject: IML: Gasoline The gasoline we bought in the good ol' days with "100+ octane" was rated by different methods, Research Octane Number [RON] or Motor Octane Number [MON]. Gasoline is now rated by averaging these two ratings [R+M/2]. There are several good gasoline articles on the web for those less technologically challenged than I, such as www.faqs.org/faqs/autos/gasoline-faq/part1/ --Roger van Hoy, '55 DeSoto, '58 DeSoto, '42 DeSoto, '66 Plymouth, '81 Imperial, Washougal, WA