Fuel economy - bad to worse

New Zealand uses RON Octane ratings, we have 91 (regular) and 95
premium. Owners manual says to use 91, which is what I use. Normally I
go to Shell, Mobil or BP. At this stage, we don't use alcohol in our
fuel. I will try to stick to one grade from one supplier and then
switch and see if that makes any difference.

TW


L.W.(Bill) Hughes III wrote:
> I don't know what your octane ratings are in New Zealand, but as
> our oil companies have had to take a lower grade of crude at seventy
> seven bucks a forty four gallon barrel, the bounce to the ounce has
> suffered. Also, here we have tried to save money by switching from a
> major suppliers of gasoline to something with alcohol in it, knocking
> off about twenty percent in economy and power.
> God Bless America, Bill O|||||||O
> http://www.billhughes.com/
>

Brakes were done two weeks ago, fuel economy went south about 3 months
ago. I might change the plugs and air filter and see that makes any
difference. Cleaning TB is also a very good idea. I have a locking
fuel cap.

Thanks for all the good ideas.
TW

PS: no teenage daughters in the house - wife doesn't drive my toy.

billy ray wrote:
> Your new brakes aren't dragging are they?
>
> What about the parking brake? some times the cables seize...
>
> Check the plugs... although if they were mis firing regularly you would get
> a p030x code..
>
> Pull off the intake resonator and take a look at your throttle body, It
> might need a cleaning with spray cleaner and an old toothbrush.
>
> http://www.imagestation.com/album/?id=2122181169
>
> The injectors might be a bit sticky, a can of Seafoam or Techron in the
> gasoline might help
>
> Be careful if you go to buy Techron. They make Techron Cleaner (pure stuff)
> and Cleaner with Techron (diluted stuff), you want the pure stuff. Both
> retail about $6-$7 (us) per bottle
>
> You don't let your wife or teenage daughter drive it do you?
>
> Do you have neighborhood youths who might be siphoning it out?
>
> What about a gas tank or gas line leak?
>
> Have you changes *brands* or octane of gasoline? It can make a difference.
>
> The last thing that comes to mind at the moment (it is 3:30 AM here) is
> driving style....... has that changed? It can alter your mileage 30-40% per
> recent tests.
>
>
>
> "TW" > wrote in message
> ...
>> Billy,
>>
>> Tyre pressure checked every week (running at 30psi), air filter replaced
>> Dec '05, spark plugs replace d Dec '04, front brake pads replaced two
>> weeks ago, diff oil changed Dec '05, ATF changed Dec '05. Any other
>> ideas?
>>
>> Thanks
>> TW
>>
>> billy ray wrote:
>>
>>> Tire pressure, air filter, spark plugs, dragging brakes, diff lube,
>>> ATF...to start..
>>>
>>>
>>> "TW" > wrote in message
>>> ...
>>>> Hi, my 01 TJ (4.0L Auto) seems to have lost whatever fuel economy it had
>>>> before. Lately, I can only do about 300kms on a full tank. I am
>>>> running 265/70R16s and an OME lift. These mods did not change the fuel
>>>> economy when they were done two years ago. Could it be that the O2
>>>> sensor has gone bad? There are no error codes or check light coming up.
>>>> Every thing else feels/runs fine. Any ideas?
>>>>
>>>> Thanks
>>>> TW
>

It has fuel injection with no distributor (uses three coils on the
rail). Total mileage done so far, 63k kms since new.

TW

Mike Romain wrote:
> Tune up time?
>
> Lots of folks forget about the distributor cap and rotor....
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
> Canadian Off Road Trips Photos: Non members can still view!
> Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
> (More Off Road album links at bottom of the view page)
>
> TW wrote:
>> Hi, my 01 TJ (4.0L Auto) seems to have lost whatever fuel economy it had
>> before. Lately, I can only do about 300kms on a full tank. I am
>> running 265/70R16s and an OME lift. These mods did not change the fuel
>> economy when they were done two years ago. Could it be that the O2
>> sensor has gone bad? There are no error codes or check light coming up.
>> Every thing else feels/runs fine. Any ideas?
>>
>> Thanks
>> TW

It could be that, I will try switching it to a different rating and
company and see if that makes any difference. NZ uses RON, where
regular is 91 and premium is 95. I use 91 from Shell, Mobil or BP.

Thanks
TW

Kate wrote:
> It could be the recent change in the fuel formulas.
> Don't know if you are running the same thing we are here in the states, but
> the new fuels decrease your mileage and sometimes as much as 5mpg like it
> did in our Liberty.
>
> Kate
>
> "TW" > wrote in message
> ...
> : Hi, my 01 TJ (4.0L Auto) seems to have lost whatever fuel economy it had
> : before. Lately, I can only do about 300kms on a full tank. I am
> : running 265/70R16s and an OME lift. These mods did not change the fuel
> : economy when they were done two years ago. Could it be that the O2
> : sensor has gone bad? There are no error codes or check light coming up.
> : Every thing else feels/runs fine. Any ideas?
> :
> : Thanks
> : TW
>
>

Well, I was never anal with my record keeping. But I do know that I
used to get around 425 kms per gas tank, which is now down to around 300
kms. Do you think that could qualify as O2 sensor drift?

TW

DougW wrote:
>
> O2 sensor drift can cause lower milage. I have noticed that as well.
> The problem is the drift is so slight it's hard to tell without being
> anal with the records.
>
> For example. http://www.revbeergoggles.com/gasminder/
>
> The pdf is just a chart of date/mpg and date/fuel cost.
>
> the spreadsheet has all sorts of stuff in it. Need to update a few
> things.
>
>

We used to use RON here, .... before unleaded gasoline came out. The
typical values were 94-95 for regular and 100-105 for premium as I recall.

Nowadays we use (RON + MON) / 2 and typically have values of 87 for regular,
89 for mid-grade, and 91-93 for premium. (octane requirements vary with
altitude)

MON measures high speed knock and RON measures low speed knock and the
rating formula change was supposed to give a more accurate overall report.

However...... at the same time the rating formula changed people started
having drivability problems with the gasoline that the manufacturers claimed
had not been altered.

I think most people assumed that the new measurements was an attempt to hide
that for the first time gasoline quality was taking a step backwards..

"TW" > wrote in message
...
> New Zealand uses RON Octane ratings, we have 91 (regular) and 95 premium.
> Owners manual says to use 91, which is what I use. Normally I go to
> Shell, Mobil or BP. At this stage, we don't use alcohol in our fuel. I
> will try to stick to one grade from one supplier and then switch and see
> if that makes any difference.
>
> TW
>
>
> L.W.(Bill) Hughes III wrote:
>> I don't know what your octane ratings are in New Zealand, but as
>> our oil companies have had to take a lower grade of crude at seventy
>> seven bucks a forty four gallon barrel, the bounce to the ounce has
>> suffered. Also, here we have tried to save money by switching from a
>> major suppliers of gasoline to something with alcohol in it, knocking
>> off about twenty percent in economy and power. God Bless America, Bill
>> O|||||||O
>> http://www.billhughes.com/
>>

Did the mileage drop happen at the same time as the start of 'Winter Blend"
gasoline?


"TW" > wrote in message
...
> Brakes were done two weeks ago, fuel economy went south about 3 months
> ago. I might change the plugs and air filter and see that makes any
> difference. Cleaning TB is also a very good idea. I have a locking fuel
> cap.
>
> Thanks for all the good ideas.
> TW
>
> PS: no teenage daughters in the house - wife doesn't drive my toy.
>
> billy ray wrote:
>> Your new brakes aren't dragging are they?
>>
>> What about the parking brake? some times the cables seize...
>>
>> Check the plugs... although if they were mis firing regularly you would
>> get a p030x code..
>>
>> Pull off the intake resonator and take a look at your throttle body, It
>> might need a cleaning with spray cleaner and an old toothbrush.
>>
>> http://www.imagestation.com/album/?id=2122181169
>>
>> The injectors might be a bit sticky, a can of Seafoam or Techron in the
>> gasoline might help
>>
>> Be careful if you go to buy Techron. They make Techron Cleaner (pure
>> stuff) and Cleaner with Techron (diluted stuff), you want the pure stuff.
>> Both retail about $6-$7 (us) per bottle
>>
>> You don't let your wife or teenage daughter drive it do you?
>>
>> Do you have neighborhood youths who might be siphoning it out?
>>
>> What about a gas tank or gas line leak?
>>
>> Have you changes *brands* or octane of gasoline? It can make a
>> difference.
>>
>> The last thing that comes to mind at the moment (it is 3:30 AM here) is
>> driving style....... has that changed? It can alter your mileage 30-40%
>> per recent tests.
>>
>>
>>
>> "TW" > wrote in message
>> ...
>>> Billy,
>>>
>>> Tyre pressure checked every week (running at 30psi), air filter replaced
>>> Dec '05, spark plugs replace d Dec '04, front brake pads replaced two
>>> weeks ago, diff oil changed Dec '05, ATF changed Dec '05. Any other
>>> ideas?
>>>
>>> Thanks
>>> TW
>>>
>>> billy ray wrote:
>>>
>>>> Tire pressure, air filter, spark plugs, dragging brakes, diff lube,
>>>> ATF...to start..
>>>>
>>>>
>>>> "TW" > wrote in message
>>>> ...
>>>>> Hi, my 01 TJ (4.0L Auto) seems to have lost whatever fuel economy it
>>>>> had before. Lately, I can only do about 300kms on a full tank. I am
>>>>> running 265/70R16s and an OME lift. These mods did not change the
>>>>> fuel economy when they were done two years ago. Could it be that the
>>>>> O2 sensor has gone bad? There are no error codes or check light
>>>>> coming up. Every thing else feels/runs fine. Any ideas?
>>>>>
>>>>> Thanks
>>>>> TW
>>
>

TW wrote:
> Well, I was never anal with my record keeping. But I do know that I
> used to get around 425 kms per gas tank, which is now down to around
> 300 kms. Do you think that could qualify as O2 sensor drift?

Yes, easily. Alas there is only one real way to test an O2 sensor,
and that is with an expensive test rig or a datalogging scope. :/
On the bright side if you put a new one in there and nothing changes,
you then have a spare.

Also, any cracked hoses, especially between the intake rail and MAP
sensor. You will know this when the vehicle refuses to accelerate
well unless you go wide-open throttle. Easy enough to find with a can
of carb cleaner. spray and listen for engine stammer.

With the coil system you have it's important to keep the plugs gapped
identically and clean. one plug out of whack will cause the sister plug
to have problems.

Another thing to be on the lookout for if you have spark problems is
the rail shorting out. I've seen one where the rail arced out internally
and was frying coils. (doubt you have this problem) But it's still worth
knowing. Another reason to keep up with the spark plug maintenance.

--
DougW

what was said to me to do here is check the carb throttle sender or more the
throttle body itself.....gummed up and covering the throttles'
sensor......if this doesn't solve the problem then you will have done a job
you should have done antway on the 4.0 ...jeep forces the reburn of stuff
that clogs the sensors at a important junction...


"TW" > wrote in message
...
> Hi, my 01 TJ (4.0L Auto) seems to have lost whatever fuel economy it had
> before. Lately, I can only do about 300kms on a full tank. I am running
> 265/70R16s and an OME lift. These mods did not change the fuel economy
> when they were done two years ago. Could it be that the O2 sensor has
> gone bad? There are no error codes or check light coming up. Every thing
> else feels/runs fine. Any ideas?
>
> Thanks
> TW

try checking the pinion angle it calibrates the tires to the speedo and the
pcm

"L.W.(Bill) Hughes III" wrote:

> I don't know what your octane ratings are in New Zealand, but as
> our oil companies have had to take a lower grade of crude at seventy
> seven bucks a forty four gallon barrel, the bounce to the ounce has
> suffered. Also, here we have tried to save money by switching from a
> major suppliers of gasoline to something with alcohol in it, knocking
> off about twenty percent in economy and power.
> God Bless America, Bill O|||||||O
> http://www.billhughes.com/
>
> TW wrote:
> >
> > Hi, my 01 TJ (4.0L Auto) seems to have lost whatever fuel economy it had
> > before. Lately, I can only do about 300kms on a full tank. I am
> > running 265/70R16s and an OME lift. These mods did not change the fuel
> > economy when they were done two years ago. Could it be that the O2
> > sensor has gone bad? There are no error codes or check light coming up.
> > Every thing else feels/runs fine. Any ideas?
> >
> > Thanks
> > TW