Both freshly prepared and steamed MFI zeolite catalysts have been tested for service life. It has been shown that the zeolite cycle length is increased from 7 to 60 days by steaming. In contrast, comparative testing under mild conditions at 300 degrees C has demonstrated low on-stream stability of the catalyst after steaming. Thermogravimetric analysis data indicate different mechanisms of coke formation on samples at 300 degrees C: polyaromatic coke is produced on the fresh sample and predominantly polyaliphatic coke forms on the steamed sample. It has been found that correct comparison of oligomerization catalysts differing in acidity requires a temperature no less than 380 degrees C, which ensures the formation of polyaromatic coke on both catalysts. As a result of the study, a rapid procedure for accelerated deactivation testing has been developed that makes it possible to obtain data comparable with those of long-term service life tests.