My 07 owners manual recommends 89 octane. It says 87 can be run if no knock s experienced and that 91+ is not recommended for use.
After any mod or engine maintenance like spark plugs its a good idea to disconnect the battery. The computers do "learn", but disconnecting the battery puts it directly into an accelerated learn mode. After a period of driving time the algorithm slows so it takes changes to the system longer to propagate.
91 Octane wont hurt anything though if your running a 91 tune through superchips. I have been running either 91 or 93 octane in my 4.7 XK for over 3 years now with now problems. Well beside the hole it makes in my wallet.
2007 4.7 Liter XK | Front Modified OME HD Lift | Rear 4" Superlift | JBA UCA's | Rusty's Rear Adjustable Track Bar | Rysty’s Adjustable Upper and Lower Rear Control Arms w/Heim Joints | Mickey Thompson Classic III 17x9 Wheels | 315/70R17 Goodyear Duratracs | Airflow Snorkel | Flowmaster 40 Series Muffler | Superchips Flashpaq | Mopar Skids | 4xGuard Belly Guard | American Rebel Rear Diff Cover | Rear Powertrax No-Slip | Front Electronic Locker | Rear Heat/AC Delete
the HEMIs have to be careful tho with the higher octanes, Im wondering tho if Im losing performance and mpg due to pre-ignition???? Seems to be an issue after researching this is a common topic. I didnt buy my XK for fuel economy but the sudden drop was concerning, Im going to start with 91 and see how it runs... This is going to be an expensive guess and check game
2K6 Limited Jeep Green Metallic/Saddle Brown Leather XK HEMI QDII Old Man Emu HD Suspension w/ Fox Emulsion 2.0 Rear Shocks 1.5" SpiderTraxx Wheel Spacers 265/70 GoodYear MTRs w/Kevlar True Dual Exhuast w/IMCO 50 K&N 63 CAI Diablo 91/Performance Transmission Tuned SA Belly Skid MOPAR Gas Tank Skid, Transfer Case Skid, Suspension Skid Front Tow Hooks 6k HID Lows/3k Fogs
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