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I have recently noticed my fuel economy is especially poor, my last tank was just over 200ks.

i changed the o2 and am almost at the half way mark on this tank at only 130ks and its worth noting i have dríven it very very easy.

The following parts have been changed over a years timeframe:

Fuel filter
Thermostat
cam angle sensor
leads
plugs a fair few times
coilpacks
o2 sensor

Has anyone had experience with this problem?

For my money, it's either O2 sensor or coolant temp sensor. You may have had a faulty replacement O2 sensor so don't rule that out.

The Coolant Temp sensor can be tested with a multimeter but is a PITA to get out.

What do you call a full tank? 50ish actual litres of petrol or the gauge reading empty. Over time the fuel gauge gets more inaccurate. Maybe you have dirty gauge connections?

Fill it to the brim run it till it stops and refill.

Check underneath and see if fuel is running out there - I'd suggest pay the money and get it tuned

Fill it till it clicks (full), run 100kms, fill it back till it clicks, measure, then re-evaluate.

If the above concludes to something that is not deemed as 'normal' or 'within range', I suggest you troubleshoot based on zossy's suggestions.

Alternatively, check spark, fuel filter/injector flow, air filter, intake carbon deposits.

48 litre tank - say 250km. Assuming filled with 10 litres still in the tank that equates to 15.2L/100km

I've always hated the idea of keeping track of km/l. It sucks the fun out of driving and my MX-5 gets dríven pretty hard so I don't expect fuel efficiency.

This year I decided to use an app with my daily driver to keep track of fuel use, it's free and called "Road Trip LE". It only tracks one car but that does me fine.

It should be a good tool for telling if my O2 sensor starts to die. On the people mover I get as low as 8.25 in summer with aircon going all the time and 10 when i'm a chilled out super commuter in winter.

It's something I've always done Okibi - takes no time and being someone who can go back almost 50 years from when I got my first carm in those days you got a good idea how the car was running - and then there were the Car Club 'economy runs' to add to that

My NA B-Spec returns around 7.5, the NB around 8.0 and the GTS86, well last fill was 6.6

I drive them no differently, nice to have a coffee then blast out to merge onto the freeway, a run thru the mountains, but, if the gauge on Narita's is 'fairly accurate' then I would be concerned - I'd almost suggest that if that's all he is getting he wouldn't see the cars behind for black smoke!!

thanks guys,

i have ordered a pre wired o2 and some new plugs, so ill throw those in when they arrive and report back, i may have just struck out with the 35 dollar o2 ...

narita wrote:thanks guys,

i have ordered a pre wired o2 and some new plugs, so ill throw those in when they arrive and report back, i may have just struck out with the 35 dollar o2 ...

My money is on coolant temp sensor (back of engine). Was getting low 200km per tank. Now get heaps more and the sensor costs $20 - $30.
I'd be changing that before replacing the o2 sensor for a 2nd time. Just my 2c

.. filled up last weekend, manage to eke out 425 km @ 43 litres on V Power