My 2001 ti pathfinder v6 ,has bad fuel consumption,it only gets about 560 k to the tank ,what is normal .and can i do anything .

Tuning for best fuel consumption means returning the vehicle as far as possible to the sort of well maintained condition the manufacturer would approve of - from the ground upwards...

While it is likely a few things will be causing the majority of the increased consumption, almost everything is likely to be having some effect and once these things have been chased down and rectified, the biggest economy device as they say "is the nut holding the steering wheel". A search should provide a video about Hypermiling.

Firstly, is there any leaks?
Secondly, is anything holding the vehicle back - binding brakes, poor choice of tyres, low tyre pressures, bad wheel alignment, incorrect grade of oil in the transmission line...

Thirdly, is something reducing the engine efficiency - poor mechanical condition, bad fuel pressures, bad injector spray patterns, tired sensors, semi-blocked exhaust, strangled intake...

By the time an engine has covered 70/80,000 miles the injector spray patterns are likely to have deteriorated enough to rob the engine of a sizeable amount of horsepower, meaning a lot more loud pedal to maintain performance, meaning a lot more fuel. This applies to everything that isn't quite right...

Your vehicle has a 15gal. tank. Km per gallon is 45 city and 62 highway. So a full tank should last around 420km around town and 585km highway. If I'm reading your information correctly then sorry to say, no. Is the engine light flashing while you are driving? If so, you need to stop using the SUV and send it in for repair before the engine is damaged. Poor fuel consumption like yours could be related to a leaking fuel injector or fuel line. A valve not seating or poor cylinder compression. Have you noticed anything out of the ordinary? For example rough idle, loss of power, hard start, smoke in the exhaust or the smell of gas? Please let me know if there is anything else.

Fuel capacity:62 liter / 16.4 U.S. gal / 13.6 imp. gal

ECE 90/120/city (comb.):
6.2 / 7.9 / 10.8 (8.3) l/100km
45.6 / 35.8 / 26.2 (34) mpg (imp.)
37.9 / 29.7 / 21.8 (28.4) mpg (U.S.)
16.1 / 12.7 / 9.3 (12) km/l

Fuel consumption simulation based on the European type of traffic:

extra-urban / city / highway / average combined:

l/100km: 7.2-8.6 / 11.1-13.3 / 8.6-10.3 / 9.5
mpg (imp.): 32.7-39.2 / 21.2-25.5 / 27.4-32.8 / 29.7
mpg (U.S.): 27.2-32.6 / 17.6-21.2 / 22.8-27.3 / 24.7
km/l: 11.6-13.9 / 7.5-9 / 9.7-11.6 / 10.5

Driving range - (km / miles on tank)
extra-urban: 715-860 km / 445-535 miles
city: 465-560 km / 290-345 miles
highway: 600-720 km / 370-445 miles

average combined: 653 km / 405 miles

no
fuel line size will not affect fuel consumption
the major item that has an affect on consumption is the fuel pressure in the fuel manifold for the injectors
next is the heated and normal oxygen sensors because if they are out of parameters the ECM will pour the fuel through the engine
next is a blocked cat converter
best advice is to run the fault codes to find out what is happening

possible in need of tune up

check air filter not blocked/dirty ? fuel leak ?

Check for a fuel leak:
1. Park the car on a clean concrete surface.
2. See if any fuel is leaking out on the underside of the vehicle.

There really are a variety of things that could cause this problem including: bad fuel filter, damaged fuel lines, or damaged fuel tank.

Another way to improve fuel consumption are getting a clean air filter.

The sending unit is part of the fuel pump assembly in the tank.
To do anything with it you must drop the tank out of the car.

an air leak would weaken the mix of fuel to air so giving you better fuel efficiency but a poor power output.
was my last answer not to your liking, re **** fuel consumption on all fiat/alpha cars.but it is true, ask any owner........14.7 average mpg.......£205 road tax.....(tax it for a year and quadruple its value...)

Brakes could be binding or hand bake cable holding on but you think youd smell burning brakes if that was the case!What condition is the oxy sensor in ,maybe carboned up and contaminated which can tell the engine management to supply more fuel than required.is the air filter air box in good condition and air box lid securely fastened.Should be sealed from air box to throttle body If the air filter is clogged and dirty that can lead to excess fuel consumption.Have you installed any injector cleaner in the fuel tank.cleans up dirty injectors thst can cause excess fuel consumption.