Ive been running the 87 tune for a few months now, had to bring my jeep back to the dealer and re-installed the stock tune, and I really felt no difference. When I re-installed the flashpaq I tried the 91 tune and felt a difference. When I gassed up I forgot to fill with 91 and had no issues. I guess my question is are there any long term issues running 91 tune on 87 gas with the flashpaq

 

The knock sensor will retard the ignition timing to prevent spark knock. As long as the system is working properly, you shouldn't have any issues. Over time (years), you may have more engine wear from the added effect of many small spark knocks.

However, you'll have less power and efficiency than if you run the proper program and gas combo.

 

what he said...