G'day, My 1994 Fairmont ED is really chewing the juice, any suggestions to increase fuel ecconomy would be great. Cheers, Will

What does it get from a tank? Make sure it is tuned and things like plugs, leads, air and fuel filters are new. Vacuum leaks especially on the MAP sensor can cause increased fuel usage. Also worth trying a new O2 sensor.

a decent set of extractors (most on here run pacemaker) and a free flowing exhaust (2.5inch) will generally increase economy as the motor works a bit easier and comes with the added bonus of power increase as well.
change diff to a 2.7.
convert to gas.
keep it serviced and tuned.
keep tyre pressures correct.
drive smoothly. look ahead and anticipate the traffic.

just a few suggestions.

your right foot?

why would u run a 2.7 diff?

that will only give u better economy when on the freeway because it makes the engine run at lower revs.

But in the city, it uses more fuel as its makes the engine work harder to move the car.

so it only depends on whether u more of a city or country traveler.

oh so the dif ratio only affects top gear? you idiot. the revs will be lower accross the range and the motor is not going to struggle. i had a 2.7 dif in a xf 5sp and that could handle 5th from 55kph. xf had 121kw vs ed 145kw. it wont struggle but it will save fuel as the engine is not working as hard. potting around at 60 it should be sitting on about 1000rpm.

injection service and clean valves up, new oxy sensor reset adaptions after that

i blew my 3.23 diff and got a 2.7 from the wreckers just to get back on the road and i cant notice any fuel economy change,revs lower but same fuel usage

how much does one cost, how does it work, is it easy to fit? etc...

was pretty cheap cant remember how much exactly,few hundred easy to fit if ya know what ya doin

'prydey' have some self control ...

i never said anything about 2.7 diff gear only affects the top gear.

i hope u realise that using something like a 3.45 diff will give your greater accleration?

now i also hope you realise that fuel is the energy source for accelerating your car. It is when the car is accelerating, that the engine uses the most fuel. When the car is not accelerating, it is using much much less fuel.

Hence, the reason why if you use a higher diff ratio (e.g. 3.45), you can potentially increase you fuel economy. By making it easier for the car to accelerate, the car spends less time accelerating making it use less fuel during this acceleration period.

However, the give away is it forces the engine to operate at a higher RPM when at constant speed. Therefore at a constant speed (e.g. at 100km on the freeway) for an extended period of time, the 3.45 give a poorer fuel economy than a 2.77.

That is the reason y, if you are a freeway traveller, its better to stick to a lower ratio diff. But, it you are city traveller, where the car is always accelerating, than a lower ratio is better.

I dont know how a xf 5 speed will feel, but in an EA factory 5 speed, the 5 gear is designed for cruising. 5 gear at 100km is about 1900 RPM. Acclerating in 5th at 60km is just asking the engine way too much. The engine shudders and you will eventually be left will a blown engine.

'prydey', please go and do some proper research. it is only something very basic ....

do you even listen to yourself . a taller dif will be more economical. since when are you accelerating all the time when driving around town. the car in question is a ed fairmont. i'm assuming auto. this means that when you put your foot down it AUTOMATICALLY changes up or down gears in the gearbox. an engine turning over at 1500rpm is using less fuel than one turning over at 1650rpm.

you are prolly one of these people who never use fifth until you hit the open road. i regularly use fifth round town. i can be in 5th from as low as 45kph and the engine is not labouring although i do have 3.45 in mine. i would not attempt to accelerate up a rise at that speed in fifth though but if i'm cruising along at 60 and traffic slows to 45 - 50 and picks up again i wont change gears. i don't slam my foot down on the gas either as i realise 5th gear is not for accelerating.

settle down girls....
*Make sure your air pressure is right
*take any extra weight outa your car that isnt nessescery..
*make sure your engine is tuned properly..
*dont leave roof racks on the car..
*dont accelerate unnesescerily between short stops..
*coast to traffic lights instead of heavy gas then heavy brake..
*drive sensibly...

*my 2c worth..

Thanks for all the help guys but um can someone tell me which diff ratio is better and yes it is an auto.

In general yes. The slower the engine is running, the better the fuel economy. BUT. There's always a but. It also depends on the cam that's in the engine. The engine is most efficiently filling the cylinders @ peak torque. As soon as you move away from peak torque, the engine becomes less efficient.

So, if you run the engine slower, you're reducing the internal friction, since the engine's running slower you need a larger throttle opening to get the same air in and hence you use less fuel. But since you're running the engine further away from peak torque, the engine's volumetric efficiency, and hence fuel efficiency is becoming less.

And before you say "Duuuuh. So if I run my engine @ peak torque, I'll get the best fuel efficiency" No. Not neccesarily. The closer you run to peak torque, the less effort the engine has to exert to fill its cylinders up with air, however, if running @ peak torque also means running the engine faster, then the increase in internal friction and other factors may end up using more fuel than you save.

This can be seen with engines with a hot cam in them where they might give better fuel economy with the engine cruising @ 2800 RPM than they do with the engine cruising @ 1800 RPM.