5.9L Question

XJGraham · 04-01-2006, 11:30 AM

Do the 5.9L Grands only run on premium? Or can I run regular as well. I am looking at getting one but people are telling me it only runs on premium is this true? Also what kind of MPG are you geting on the highway with them?

agoldxj · 04-01-2006, 11:34 AM

ive heard premium only...

Vetteboy · 04-01-2006, 12:12 PM

Premium only, and even then it might knock a little bit.

I get 16.5ish on the highway, commuting to work and back. About 70% go, and 30% stop-and-go. Seems to get a little better gas mileage if you do push it a little bit, for whatever reason.

Aidan · 04-01-2006, 01:34 PM

Yea, definatly premium for the 5.9. My parents old 5.2 used to knock as well so it had to be run on premium.

offroadzj · 04-01-2006, 06:22 PM

premium only!!!. I once added regular by mistake (had been driving my dd around, and just grabbed it by habit). After about 1/4 tank i couldnt stand it anymore and siphoned out all the regular and put premium back in. It knocked like you wouldnt believe.

wsuxjer · 04-02-2006, 01:18 PM

Premium only but there was a "neuter" flash that allowed them to run on 87, for the cost of some HP.

04-01-2006, 11:30 AM	#1
XJGraham Trail Guide Join Date: Dec 2002 Location: Kitchener, ON Posts: 165	5.9L Question Do the 5.9L Grands only run on premium? Or can I run regular as well. I am looking at getting one but people are telling me it only runs on premium is this true? Also what kind of MPG are you geting on the highway with them?

04-01-2006, 11:34 AM	#2
agoldxj i'm special Join Date: May 2003 Location: catawissa pa Posts: 14,462	ive heard premium only... __________________ 2013 6spd JK

04-01-2006, 12:12 PM	#3
Vetteboy glamour turquoise Join Date: May 2003 Location: Red Bank, NJ Posts: 16,704	Premium only, and even then it might knock a little bit. I get 16.5ish on the highway, commuting to work and back. About 70% go, and 30% stop-and-go. Seems to get a little better gas mileage if you do push it a little bit, for whatever reason. __________________ trail rig: '94 XJ, 14FF, D60, Nv4500, D300, NP231 doubler box, 38.5 Creepies, chopped, caged, MJ'd. Wheeling. DD/tow: '05 Dodge 2500 CTD 6-speed. Wheelin '09...time to have fun. Hammers: x Rausch Creek: xxxxxxxx Uhwarrie 4x4cross: x Line Mountain Miler: x Big Dogs: x RCRocs race: x (= dead xj) Wheelin '10...time to go faster.

04-01-2006, 06:22 PM	#5
offroadzj Trail Guide Join Date: Jun 2005 Location: Albany, NY Posts: 128	premium only!!!. I once added regular by mistake (had been driving my dd around, and just grabbed it by habit). After about 1/4 tank i couldnt stand it anymore and siphoned out all the regular and put premium back in. It knocked like you wouldnt believe. __________________ 1994 ZJ 5.9 swap, Rock Krawler 7" LA kit, 35" Super Swamper TRXUS M/T mounted on 15x8 pro comp extreme alloys. Axles on the way (locked, 4.10 gears)

04-02-2006, 01:18 PM	#6
wsuxjer Wazzu! Join Date: Aug 2002 Location: Tacoma, WA Posts: 1,256	Premium only but there was a "neuter" flash that allowed them to run on 87, for the cost of some HP. __________________ www.pnwjeep.com