gu '98 patrol 4.5 petrol

Hi Livo308

You won't improve the economy with those sorts of mods.

They can however improve your peak power for those few seconds when the throttle is flat to floor
or when the engine revs over 3600 rpm when the computer switches to WOT mode (Wide open throttle).

Those engines efficentcy is controlled by their fundamental reference which is the oxygen sensor.
You can double the size of the air intake and the ECU will sense a lean condition and re-adjust to compensate.

Replacing the oxy sensor usually improves economy because the sensors get tired and their reference setting drifts to rich.

You should be looking at 17lt/100km if car is unmodified , I'd start by recording your consumption and running it with 40psi in the tyres.

Mate I can't fault mine...yes they are a little thirsty but the power is good and they are a very capable off-road vehicle. My economy used to be around the 20l/100km but I had a faulty oxy sensor and after I replaced that and did a dyno I was getting around the 16-17l/100km. I would not swap it for anything and once that motor goes I will get the V8 to go in. I have pacemakers extractors and sports exhaust system and you gain some horsepower but not really fuel economy I really like the shape of this model and you won’t be disappointed!