Hi all

Got my mazda 6 1.8 on an 06 about 3 weeks ago until now ive noticed that the trip computer is reading 18mpg and can go as low as 15mpg ive driven it sensible.

No engine management light on
Starts up fine cold or hot.
Idles ok around the scond white line from 1000rpm.bit a slight limpy around that area hardly noticeable but its there!
Takes about 5/10 minutes to warm up even at a temperature of around 6c

Things ive done so far..
Checked for fuel leaks
Sprayed carb cleaner on vacuum hoses
Checked the carb for dirt etc... (felt inside and my finger was black OIL? )
Sprayed carb cleaner inside.
All the above no difference

As I said I haven't been thrashing it around been driving like an old man. At the moment its doing short journeys but for a 1.8 this isnt righ! What sort of mpg should these do?

Or is my car trip computer reading wrong!?
About a tenners worth of fuel I get like 35/40 miles out of it.
Thx for any help much appreciated.

 

Many things to do:
Hi miles: change plugs, ign coils

Really hope this is a gas vehicle (now it's 2 important things not given, and as a result this will be my 1 and only post for this!)

Lower miles:
Change PCV Valve, clean EGR valve, clean throttle body, clean MAF sensor, put in fuel system cleaner. Change throttle body gasket as it's best to partially remove throttle body and catch gunky spray with paper towels/rags.
I'm quite sure PCV valve was never changed as Mazda never changes it. They can be tricky on 4 cyl engines but a must!
While doing above disconnect the negative terminal on the battery followed by a few brake pedal applications.
After above is all done, re-hook up battery and let idle for 5-10 minutes. Now car will start to re-learn. for next 50-100 miles.
You will have to re-program your passenger window as well. This is done by lowering the passenger side window from passenger side. While putting up that window you need to also put up the window at the same time with the driver side control and hold both controls up for 20 seconds after the window has returned to top.

READ and watch: Rough Idling Issues | MotorWeek





If this doesn't help, you'll need to change your O2 sensor before the pre-cat!
A defective O2 sensor will likely cause your air-fuel mixture to be too rich and directly affect your fuel economy,
From: https://www.oilfiltersonline.com/blo...our-o2-is-bad/

 

IIRC, there is no PCV valve, but it's rather an orifice that could need cleaning and is in one of the hoses.
Also, you say you've using it for short trips. This too will kill fuel mileage, and eventually the rest of the engine too. The fluids need to come up to full temperature in order for the engine to run correctly and efficiently.
Example: I once owned a Mitsubishi, but only lived 1.2 miles from nearly everything I needed, so the car hardly ever got up to temp, and only got 15mpg. I moved away and was driving it 20 miles one way each day. My mileage went up to 25mpg, but some damage had already been done. With <80k miles on the odometer, the valve seals were starting to leak, valve guides wearing and I was getting blow-by on the piston rings too. I started using/burning oil and it was all down hill from that time on.

 

He also could be in Siberia for all we know, or Northern Alberta as well. Then the mileage would be OK!

 

Thx for comments.
Im from the uk 8/10c so not very cold at wouldn't. Cause my mpg.to drop that much.

Had a run on the motorway last night a trip of about 15 miles at 60mph I was averaging 10-12 mpg! Lol..I wouldn't mind if I was driving a Ferrari.
Gonna try the complete system cleaner but can't see that doing anything!
I think the cars is fuked doing those mpg anyway.
I dont want to spend time and money on it when im trying to get tid off it anyway.

 

Have you actually checked the mileage in the traditional way, or are you relying on the onboard computer to tell you.
Trip computers are rarely that reliable, though that is a pretty far off what it should be. Usually 1-3mpg off. But you should make sure you are not being fooled by a computer which may not be accurate, or have sensor issues.
Also, using twice the fuel it should be using, it's got to be going somewhere? If nothing else, out the tailpipe. And if the engine is dumping unburned fuel, the catalytic converter would be literally working over time to compensate. It should be excessively hot and will have a very short life if this is happening.