the manual recomends prem. fuel.
if you use regular and add octaine booster will you get the same results?
thanks

 

Welcome to the forum doggbone47,

I've moved your question from General Tech Help forum to XJ40 forum.

Members here with the same model as you have will be ably to advise on fuel requirements for your 1989 XJ6.

Graham

 

dogg-

99% of the octane boosters found on auto parts store shelves are useless snake oil- just read the labels and how they avoid making hard claims.

.9% of the remaining products do work but you'd go broke buying enough to boost the fuel to the required octane level.

The remaining .1% can boost octane to a decent level but in addition to being expensive, will destroy the cat convertors due to the lead content.

It's always, always cheaper to buy the correct octane fuel at the pump .