Rating gasolines at the Bureau of Standards. Washington, D.C., April 17. F.R. Carter of the U.S. Bureau of Standards is shown adjusting the mixture of gasoline to find out the rating in octane numbers of gasolines. The three carbureter shown in the foreground are each filled with a gasoline tow of which with a known octane rating and the third is filled with the sample to be tested, this machine has a variable compression ratio and can be changed while in motion