Forgot to mention, a "premium" tank of non-ethonal (filling up my lawn equipment at the time). The "efficiency" gained was much, much less than the cost of the fuel. Again, pointless to run anything other than cheap 87 pump gas.
What octane and type of fuel does your 4.0 like?
- Thread starter AndyG
- Start date
Am i following along correctly? Some people are talking about running cleaner fuel, others are talking about premium vs regular.
Or are they the same topic?
I thought the debate was settled.. the 4.0l is designed for regular fuel. No need for 92. Says so in owners manual.
But are some advocating for fuel from the Am Pms of the world and 711s over shell and mobile with their detergents?
Curious.
Or are they the same topic?
I thought the debate was settled.. the 4.0l is designed for regular fuel. No need for 92. Says so in owners manual.
But are some advocating for fuel from the Am Pms of the world and 711s over shell and mobile with their detergents?
Curious.
I've run 87 in mine since I bought it.. but I do dump in a bit if 100LL Avgas on occasion when I get a bucket of clean sump fuel from work. Makes my Jeep smell good. I've run Avgas in my lawn mower as well. Smells like an airplane lol
CAJACK
Member
Haha, yep! OP asked about octane and type, so we have been covering all the bases. Bottom line, for the TJ any 87 octane will work (or 91/92 if you are in a RON country).
I did get a misfire on my PCM when I was out in CO. I changed the plugs and the coil pack and it went away for a while. When it came back I tried putting mid grade in it and it went away again and did not come back..... now a couple of variables: I was at altitude (most of the time 7,000 +), I was towing my M416 off road camping trailer fully loaded, the wife, dog, and whatever else got shoved into the LJ while I was not looking, and we were running pretty hard (I was the only Jeep in the group, everyone else was in Toyota 4runners.....). Coincidence? Maybe, did I push it harder than I normally do, absolutely. Normally I burn 87 and it does just fine......
If 86 is the lowest in your region, then yes. Colorado typically uses 85 because of the increased altitude.
There are a few big problems with ethanol in the fuel.
1) it attracts moisture to it
2) it contains fewer BTU's of energy than normal gasoline
3)AND THIS IS A BIG ONE...
It is a very good solvent.
At some point car manufacturers made all the fuel hoses ethanol safe. Prior to this though running ethanol will start to dry out and dissolve many of the plastic and rubber pieces in the fuel system.
The solvent will also rapidly start to dissolve all sorts of gunk inside the fuel system causing (mainly in a carb engine) small orifices to plug up.
Most all other engines have not been redesigned to run ethanol. This includes many lawnmowers, weed walkers, chainsaws, etc.
For these it is far better to run ethanol free fuel. On our older tractors the ethanol dissolved all the gunk so carbs started to leak out of every gasket and seal.
Quite a few years ago NY passed a law that any gas station can sell any brand of fuel. So you might be getting anything at a Mobil station. As earlier stated they all just buy from the bulk tanks at the Albany harbor. My 06 does run a bit stronger and smoother on 87 (with required ethanol) than on super 91 (non ethanol)
So I'm hoping that by 06 the fuel system was designed for ethanol use. Cheaper and runs better I like. Plus not knowing what former owners have run in it makes paying for the premium silly, tho for all other engines i have on the farm i use only the premium ethanol free fuel.
1) it attracts moisture to it
2) it contains fewer BTU's of energy than normal gasoline
3)AND THIS IS A BIG ONE...
It is a very good solvent.
At some point car manufacturers made all the fuel hoses ethanol safe. Prior to this though running ethanol will start to dry out and dissolve many of the plastic and rubber pieces in the fuel system.
The solvent will also rapidly start to dissolve all sorts of gunk inside the fuel system causing (mainly in a carb engine) small orifices to plug up.
Most all other engines have not been redesigned to run ethanol. This includes many lawnmowers, weed walkers, chainsaws, etc.
For these it is far better to run ethanol free fuel. On our older tractors the ethanol dissolved all the gunk so carbs started to leak out of every gasket and seal.
Quite a few years ago NY passed a law that any gas station can sell any brand of fuel. So you might be getting anything at a Mobil station. As earlier stated they all just buy from the bulk tanks at the Albany harbor. My 06 does run a bit stronger and smoother on 87 (with required ethanol) than on super 91 (non ethanol)
So I'm hoping that by 06 the fuel system was designed for ethanol use. Cheaper and runs better I like. Plus not knowing what former owners have run in it makes paying for the premium silly, tho for all other engines i have on the farm i use only the premium ethanol free fuel.
Aviatortroy
TJ Enthusiast
I definitely prefer ethanol free, there are several Murphy USA stations around that have it and it’s the same price as the mid grade. So if I get a few percent better gas mileage out of it it’s a wash and runs noticeably better, without dissolving my fuel system.
Aviatortroy
TJ Enthusiast
The later TJ fuel “burp” gas pump overflow problem is basically 100% attributed to ethanol causing the shutoff to swell inside the tank and not work. Also I strongly suspect ethanol fuel led to my fuel pump meeting an early demise at only just over 100,000 miles.
Raymund
TJ Enthusiast
Stick to the recommended one as per the manual.
I have used higher octane and have noticed better mileage though. But I still stick to 91RON in Australia (equivalent of 87RON there I believe)
I have used higher octane and have noticed better mileage though. But I still stick to 91RON in Australia (equivalent of 87RON there I believe)
Only "Premium" is allowed to be ethanol free in NY. That's why we run it for the farm equipment.
I had an old Escort EXP(?) that had such bad pre ignition it couldn't do highway speed on 87. Had to run 91 to be driveable.
But that was an extremely crapped up engine.And a long time ago. And only ran on HESS brand.
Most vehicles get better mileage on regular but with 87 we have 10% ethanol. So cars tend to get slightly better mileage using ethanol free 91. Not enough to justify price jump though.
Aren't there cases of preignition in an unmaintained engine where higher octane fuel masks the fundamental problem? Similar to a steering stabilizer "fixing" death wobble?
Ive always ran 87. Some spots in Wyoming only sell 85, 88, or 89 and Ive ran them with no ill effects. I typically buy my fuel from a Conoco, Texaco, or P66 station. Ive worked on their refineries (mostly in the western US) and they seemed like real clean facilities. I spent 8 months at a Sinclair refinery in Cheyenne Wyoming and about 3 months at another Sinclair refinery in Sinclair, Wyoming. Both were horrid. Plumes of product in groundwater, soil, and spills, numerous health and safety violations, run down and leaking facilities. I wont buy fuel from any Sinclair, Flying J, or Loves station.
You guys are all crazy. All I ever put in my TJ was 110 race octane from the local VP fuel station.
No idea why anyone would put 87 octane in their TJ
I also only used the most finest synthetic oil known to man, because it makes my 4.0 faster!
No idea why anyone would put 87 octane in their TJ
I also only used the most finest synthetic oil known to man, because it makes my 4.0 faster!