Should you only use higher octane gas when trying to achieve peak performance? If I'm just cruising on the freeway and going up a few hills, is 87 octane fine?

 

Hi mdantonio95,

The Jaguar AJ6 engine in our XJ40s was designed to run on "Premium" grade fuel. Off the top of my head, I think the owner's manual for our 1993 XJ6 specifies the minimun acceptable octane is 91 (by the standard used in the U.S.: different standards are used elsewhere).

I know a couple of owners who use "Regular" grade fuel in their XJ40s and claim they have no trouble.

The AJ6 was designed to run on higher-octane fuel, which has an increased resistance to detonation and pre-ignition compared to lower-octane fuel. Unlike the AJ16 engine introduced in the X300, the AJ6 has no knock sensors to tell the Engine Control Module when detonation or pre-ignition occurs, so the ECM can't respond by retarding the ignition timing to eliminate the knocking. And the AJ6 engine is so silky smooth and quiet, it can knock a lot without the driver even realizing it.

We report, you decide.

Cheers,

Don

 

Thank you for your reply Don. It's nice to know that there are fellow Jaguar enthusiasts that are willing to help you out when you have questions. Many thanks!

 

You're welcome, mdantonio95.

By the way, I notice that you have not yet posted an introduction. Please visit the New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum and post an intro so we can give you a proper welcome and so we can learn something about you and your Jag.

Cheers!

Don