I was out of gas, pulled up to 7/11 and they only had regular gas.
I went ahead and put in the regular even though I always use Premium.
I have a 2004 XJ8. It was not running well the 1st quarter of a tank, now the "engine failure light" is on and I limped back home at 30 miles per hour.

I live 3 hours from nearest Jag dealership.

Any suggestions!

I feel so stupid...it would have been better to run out of gas!

Help!

 

I doubt theres a connection. I havent used premium in years and I know many customers that dont either. If you dont have an R, dont tow, dont haul 4 linebackers for freinds around or haul azz up hills and mountains that all increase engine load and lugging. youll be fine without premium, thats why there are knock sensors to retard timing in the event of poor gas quality, and or engine loading that creates pinging

 

Perhaps the fault is IN the previously seldom used knock sensors. Fill with premium (and/or add some octane booster to what you have left), clear the codes (after reading and writing them down) and with luck, back to normal.