Grade of Gas - Page 2 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > WK2 Grand Cherokee Forum > Grade of Gas

Brand New! Quadratec LED Headlights!FS: 2007-2013 Jeep Wrangler "HALO" Angel Eye KitFS: Wranger BRIGHT License Plate LED! Just $3! Great value

Reply
Unread 07-25-2013, 11:13 AM   #16
Kev M
Registered User
2012 WK 
 
Join Date: Jan 2006
Location: Medford, NJ
Posts: 668
Quote:
Originally Posted by ColdCase View Post
I think we have a failure to communicate. You seem to keep wrapping your head around a knock sensor an that was not what I was saying. I did not mention knock sensor, but a what is commonly called a predestination sensor or prediction algorithm.. Nothing like a knock sensor. Harley users a what the call an ion sensor system.

Bottom line is that, for the WK2, listening for ping and hearing none gives you false information.
My bad - I came back from a run and did some research. You caught me as I was trying to edit my post.

You might be right - or at least more right than I thought.

My switch from the automotive to the motorcycle and marine industries has left me a little lagging behind in that tech. I'm still seeing pezo knock sensors used, at least in the marine industry. I had forgotten about the Harley ION sensing systems on BTs (and didn't realize they went back as far as they do).

So you're right, it might be far more widespread.

That said, IF IT IS, that makes octane a much less important issue, since those systems are much more sensitive and better at preventing knock before any damage can occur. Yes?

Kev M is offline   Reply With Quote
Unread 07-25-2013, 11:17 AM   #17
Kev M
Registered User
2012 WK 
 
Join Date: Jan 2006
Location: Medford, NJ
Posts: 668
Quote:
Originally Posted by ColdCase View Post
Harley users a what the call an ion sensor system.... That is also used in many new sportsters.
Well, a year or two ago, last time we checked into it on the XLforum that logic was NOT used in the Sportster ECMs. That might have changed by now, but I haven't heard of it.

Certainly I know for certain it was not used at LEAST 07 (introduction of the EFI Sporty - we have one) through 09 or 10.

I'd have to check with someone who has data-logged or gotten into the OEM maps of a later model to tell you for sure if it's still the case.
Kev M is offline   Reply With Quote
Unread 07-25-2013, 02:10 PM   #18
jim_in_PA
Registered User
2012 WK 
 
Join Date: Jul 2012
Location: Bucks County, PA
Posts: 491
I believe the reference to 91 octane in the manual is a mis-print...I seem to remember this coming up several times in the last year.

FYI, I run 87 exclusively...and average about 16-17 in normal rural driving and 20-21 on the highway for distances.
__________________
2012 Grand Cherokee Overland Summit 5.7L V8 - Winter Chill with New Saddle Interior
jim_in_PA is offline   Reply With Quote
Unread 07-25-2013, 04:31 PM   #19
Butterjeep
Registered User
2012 JK Wrangler 
 
Join Date: May 2012
Location: Edgewater, NJ
Posts: 495
Running the 87 at altitude is the same as running the mid at sea level. OP, you'll be fine. I lived in Denver for 7 years and even the dealers would say 85 is fine when regular was specified and 87 was fine when mid grade was specified.
__________________
2012 JK
2014 WK2
Butterjeep is offline   Reply With Quote
Unread 08-20-2013, 10:28 AM   #20
bikerbill7
Registered User
 
Join Date: Nov 2006
Location: Naperville, IL
Posts: 42
Gasoline is gasoline, and contains the same explosive power, no matter which grade you use. Octane controls the burn (flame-front).

Too little octane for that engine-type means the gasoline may self-ignite from the high temperatures in the combustion chamber, pressure of the rising piston, or a hot-spot deposit on the piston or in the cylinder. This is called pre-detonation (ignition before the spark plug fires). When the spark plug finally ignites, you'll have two combustion wave fronts. When the two wave fronts collide, you'll get knocking. The PCM will retard the timing, lowering your optimal performance. This happens so fast, you won't even know it.

Too much octane for that engine-type means when the spark plug ignites the fuel mixture, the flame front is so slow that your don't get a complete burn, lowering your optimal performance. This unburned fuel goes out through the exhaust, affecting your emissions systems, specifically your catalytic converter. Also, because the exhaust stroke of the 4 stroke engine doesn't completely evacuate the cylinder, unburned fuel molecules remain in the combustion chamber, and will be deposited onto the piston, eventually building up, raising your compression ratio, requiring you to burn premium gasoline to stop pre-ignition.

Higher compression engines create more pressure and heat in the combustion chamber, just before top-dead-center. That's where your power comes from. Remember 13.5:1 compression ratios that required 104 octane? I know - I'm old...

Engineers have designed their engines for a complete burn, and recommend a specific octane to accomplish that. It's that complete burn that will give you the most power and mileage.
bikerbill7 is offline   Reply With Quote
Unread 08-20-2013, 08:22 PM   #21
overland_HO
Registered User
2013 WK 
 
Join Date: Jun 2008
Location: SLC, UT
Posts: 233
Quote:
Originally Posted by Wasatchwk2 View Post
I know, I did read the sticky. It says the 5.7 is tuned for 89 and can run fine on 87, however, I was reviewing the manual and it says recommended for optimum preformance to use 91 octane.

So I was just wondering what everyone is using for their 5.7? I was planning on filling up with 87, I just wanted to be certian that this will not effect the engine in anyway.

Thank You,
We run either 87 or 91 in our HEMI, mainly 87 through and 91 every other fuel up or so. 89 is not readily available around here just 85,87 and 91 and sometimes you can find 89...
__________________
13 Jeep G.C. Trailhawk HEMI/QDII/QL/ORAII
14 Chevy 3500 Duramax/Allision
overland_HO is offline   Reply With Quote
Unread 08-21-2013, 03:16 PM   #22
howardusa
Registered User
1996 XJ Cherokee 
 
Join Date: Jan 2006
Location: , Missouri
Posts: 405
I operate just fine on a balony sandwich but will operate at maximum performance eating steak. I use 89 octane in my 5.7l cause it's recommended. Saying it's OK to use 87 is not good enough for me. It's your Jeep feed it what you like, I feed mine what the Jeep likes.
HT
howardusa is offline   Reply With Quote
Unread 08-21-2013, 06:05 PM   #23
Jpiwonski
Registered User
2011 WK 
 
Join Date: Apr 2013
Location: Simsbury, Ct
Posts: 99
I know all of the Vette guys use http://www.toptiergas.com/ to buy their gas as the additives and everything is controlled more at these stations.
Jpiwonski is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.