I know this has been done to death, but I couldnt really find anything on here to address my issue.
Few years back I had a TJ manual with cai+KnN and redback muffler, I was consistantly getting mid 7Lper100kms on the highway.
Now with my TH (same 3.5ltr engine 5 speed manual, same cai+KnN and muffler) Im finding it hard to get below 9Lper100kms on the highway. Ive changed and flushed the oil a number of times, had the bottle of injector cleaner in my tank, changed the o2 sensor for a brand new one, still no change.

Any ideas would be appretiated.

Cheers

Attila

my guess is olders cars consume more fuel, 9ltr/100 is pretty good. my old te was 11ltr/100km

Could also be different wheels and tyres and also tyre pressures? Got mags or anything?

Ollie

Everything is standard or the same as on my old TJ, and older cars only consume more because there is something wrong (besides the TJ was a 2000 model aswell so really it should be the same).
Im thinking bearings in alternator or aircon, or something on the belt pulley side of the engine.

Few years back I had a TJ manual with cai+KnN and redback muffler, I was consistantly getting mid 7Lper100kms on the highway.

The above statement doesn't sound right. If it is true - you must have been averaging it over a very limited distance (for example - resetting the trip computer while you were already on a highway traveling at highway speed and then concluding that that was your average before you exited the highway).

Everything is standard or the same as on my old TJ, and older cars only consume more because there is something wrong (besides the TJ was a 2000 model aswell so really it should be the same).
Im thinking bearings in alternator or aircon, or something on the belt pulley side of the engine.

The TJ's had a slightly different cam profile didn't they? that could contribute to the better fuel economy

The above statement doesn't sound right. If it is true - you must have been averaging it over a very limited distance (for example - resetting the trip computer while you were already on a highway traveling at highway speed and then concluding that that was your average before you exited the highway).

Thats exactly what I'm saying, I drive on the highway alot and sometimes I refuel (therefor reset the trip comp.) on the highway.
I'm doing the exact same route (syd-canb) and even use the same servive stations as I did with the TJ.

Tmrw I'm going to change the rear bank platinum spark plugs, they havnt been done for 60,000kms. I havnt noticed a decrease in performance because of this but at 60,000kms you never know. (BTW I don't believe in leaving these for 100,000kms like the manual says to do)

Cheers for the replies

The trip computer in a 380 will tell all . . .

Instantaneous readout:
Heavy foot around town = 16 - 24 L/100Km.
Light foot on freeway, at 100KPH = 6.5

Average: 11.5L /100Km over 30,000Km.

So - it depends on how you drive. and even comparing two supposedly identical cars, there are many differences - computer air/fuel mapping, ignition mapping, weight of car, tyre brand, size, pressure, rolling resistance. Not to mention engine tune, state of wear, oil viscosity, actual water and oil temperatures, etc. Did I mention auto box friction and shift pattern mapping? mmmmm??

Weren't there adjustments made to the engine for the TJ, like tweaks to the engine management and stuff? I'd think that to be a factor as well.

I get around 8-8.5L/100kms on my KH 3.5L, strictly highway. That rises to 12-13.5L/100km with the amount of around-town driving I do.

The TJ's had a slightly different cam profile didn't they? that could contribute to the better fuel economy

Exactly what I was thinking, the main reason for the cam profile revision was for better fuel economy and a slight bit more power/better breathing at higher revs.

Yeah the difference in TH and TJ could be right.
I reset the computer just before departing canb. and it went down to 8.0l/100kms, and even hit as low as 7.9l/100kms for a bit.
I hadn't reset the computer after I installed the KnN a while ago thinking it will adjust by itself like its supposed to according to popular belief.

Something to think about........

Cheers

Attila

Understanding your problem of confusion between cars of similar age.

I have it with the same car. Driving to Melb from Gippsland the TH 3.5 Exec with 240,000k's gets 8.5lt/100, but this weekend driving back filled up at a Liberty, Boost 98 used. Driving to Longwarry had it at 7.1lts @ 100km/h soon as 110km/h up to 8.2lts for the next 150ks. Tyres 34psi. Use the Instant fuel guage to try and get an idea of your driving.

When i changed back plugs 2weeks ago noticed build up black crap in inlet manifold and pc valves. Fuel injector cleaner won't clean this as it is not involved in fuel delivery injector. Pulling it apart is only way.

Cleaned airflow meter on my diesel 4wd and it made an immediate difference to power and economy. Went from 13.5/100 to 11.2/100 increase in tyre pressure to 33psi and a gentler pedal.

Understanding your problem of confusion between cars of similar age.

I have it with the same car. Driving to Melb from Gippsland the TH 3.5 Exec with 240,000k's gets 8.5lt/100, but this weekend driving back filled up at a Liberty, Boost 98 used. Driving to Longwarry had it at 7.1lts @ 100km/h soon as 110km/h up to 8.2lts for the next 150ks. Tyres 34psi. Use the Instant fuel guage to try and get an idea of your driving.

When i changed back plugs 2weeks ago noticed build up black crap in inlet manifold and pc valves. Fuel injector cleaner won't clean this as it is not involved in fuel delivery injector. Pulling it apart is only way.

Cleaned airflow meter on my diesel 4wd and it made an immediate difference to power and economy. Went from 13.5/100 to 11.2/100 increase in tyre pressure to 33psi and a gentler pedal.


Every now and then I spray about half a bottle of throttlebody cleaner into the PEV while the car is running. The revs drop and it wants to stall but you just have to keep the revs up at about 2000rpm. I would highly recommend this to anybody who hasn't done this already to there car (with a few k's on the clock), it cleans the TB, plennum and combustion chambers out and in some cases clean the sticky grime off the inlet valves that sometimes cause a ticking sound.
You'd be surprised how much better and smoother the engine runs after.

Having said this I do clean the TB and plennum out when I take it off, incredible how much crap builds up in there.

BTW if anybody decides to do the above mentioned procedure, be aware that there is a remote chance that it can damage the TPS.

the other day was working on a TL by memory and came across the most biggest con i have seen fuel savers and 2 hi clones, which are about 170 each off the top of my head. i believe they dont work but has any one used them and had results? either on a dyno sheet or has proven fuel economy. you cant compare fuel economy to another vehicle of the same make and model, as they have different drivers, traffic conditions, etc

Using throttle body cleaner is the best, usually do it when changing rear plugs, spray about 1/3 of the can down the runners before you chage the plugs to let it do its job and then spray a little more before you refit the planuem . Takes a bit to start up afterwards, full throttle and crank it until it starts and look at the back, clouds of smoke :D lol to the guys across the workshop, they're smokin :bowrofl:

With regards to camparing fuel consumption of different cars, I believe you can on the same stretch of road, the same constant speed, tyre pressure etc.

Using throttle body cleaner is the best, usually do it when changing rear plugs, spray about 1/3 of the can down the runners before you chage the plugs to let it do its job and then spray a little more before you refit the planuem . Takes a bit to start up afterwards, full throttle and crank it until it starts and look at the back, clouds of smoke :D lol to the guys across the workshop, they're smokin :bowrofl:


Spraying it into the throttlebody when the engine is running is even better.

Why would you want fuel economy when you can have power?

doesn't smoke up as much lol

by the way if you get your vehicle serviced at a mitsu dealership, they will prob try and sell you an injector flush, biggest load of crap ever, but you didn't hear it from me :D also the power steering flush biggest waste of money

the other day was working on a TL by memory and came across the most biggest con i have seen fuel savers and 2 hi clones, which are about 170 each off the top of my head. i believe they dont work but has any one used them and had results? either on a dyno sheet or has proven fuel economy. you cant compare fuel economy to another vehicle of the same make and model, as they have different drivers, traffic conditions, etc

I put a Hiclone on my old Ford Laser carby. They are supposed to work better with carby's, and people say they dont do ****, but believe me, there was DEFINITELY a change, im sure there was more power, but I know definitely the car ran smoother, it sounded less rough, especially in the top end, I always felt like reving it up to redline once I had it in, but when I took it out, I kept shifting at about 5000rpm without thinking.

Now they are supposed to save fuel, but although there was more power, probably as a result of being such a weak engine and me thrashing the engine all the time, fuel consumption I think actually went up a bit.

Was thinking of trying one in my car now, though with the sophisticated fuel injection and AFM's not sure if the same effect will happen. Though now that I think of it, the have a money back guarantee, so I might just give it a try. I have been logging my fuel consumption VERY accurately for about a year now, so I can compare fuel consumption at least. Otherwise I would be more than happy to go back and tell them that their product is a load of crap.

Ollie

To my knowledge, hiclones are a hit and miss for fuel economy. Sometimes they work on some cars and others they dont. Some people have evidence for it others dont. Maybe research which cars have had success with hiclone and see if any are Magnas, if you are looking at that sort of thing. I know on the brochure it does say a guy in his KF Verada I think gets better economy on the highway but my personal short lived experience in a 4cyl 2nd gen proved nothing :)