Author Topic: Poor fuel economy? *Please read this!* (the *definitive* poor fuel economy topic)  (Read 34713 times)

Jazzman84

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It is winter my mpg dropped from 56 mpg in summer to 47.5 mpg in winter

SuperCNJ

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Yep winter plays a big part in reducing mpg. Firstly air temp is lower so more oxygen so more fuel is needed, secondly you use your wipers, heaters and headlights more and also oil and cat takes longer to reach operating temp when it is most efficient. If you use winter tyres, their rolling resistance is higher, so less fuel efficient and finally drivers are more cautious in the winter and I find are generally much slower around town when its wet, so I tend to get stuck in traffic/at traffic lights for longer than usual.


 

andrew h

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Hi,

Both I and my wife have Jazz's, 04 and 57 respectively and both of us experiencs massive drops in efficiency during the winter months.  I would guess that it drops by around 20%.

Still love the cars though.

Regards,

Andrew

hondajazz2003

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Thanks everyone !

Yes, I thought about that however, 38 miles/gallon is the minimum efficiency I have noticed. I remember whole last winter, the efficiency didn't drip below 38 mpg. Also,I have this issue for last three months  when it was Autumn and not much cold too. I spoke about this to the guy who serviced my car( F1 Autocentres) and he recommended a fuel treatment that cleans up engine etc though I am not sure its worth trying?

Many thanks
PK

DV

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I spoke about this to the guy who serviced my car( F1 Autocentres) and he recommended a fuel treatment that cleans up engine etc though I am not sure its worth trying?

Many thanks
PK

I`d use premium fuel 2-3 times, it has all the treatment additives already in it...
When was your all 8 spark plugs last replaced?
You must run short distances to get below 40mpg... I cannot go below 43mpg by gentle driving in winter.

culzean

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I spoke about this to the guy who serviced my car( F1 Autocentres) and he recommended a fuel treatment that cleans up engine etc though I am not sure its worth trying?
Many thanks
PK

First off I would try Redex rather than premium fuel,  a 500ml bottle to treat 4 tanks will set you back about 8 - because it is the first clean for a while ignore the advice about dosage and just tip half bottle in first tank and then follow up with half the rest into next tank, and empty bottle into third tank.  It's almost impossible to overdose with Redex.  After initial clean I would use premium fuel every 2nd or 3rd tank to keep everything in good shape.
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

madasafish

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I have tried Redex and premium fuels. None has made any measurable difference. I keep accurate records.

Redex worked well in the days of low quality fuels and incomplete combustion due to the use of carburetors/manual chokes/ early fuel injection. But today's fuel injection systems measure very accurately, cars can run well over 100,000 miles without having to decarbonise the cylinder head and parts like injectors are made to very fine tolerances.


In my view , a waste of time and money.

If your car has levels of dirt and carbon due to the use of EGR valves, a clean of the EGR valve and air intake and throttle body are far more effective. And also any air sensors in the air intake -they end up being covered in a layer of fine dirt.

SuperCNJ

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Could it be a seized caliper perhaps?

IvyTek

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[quote Could it be a seized caliper perhaps?[/quote]

Really worth checking out.

Short of jacking the car and spinning each wheel by hand to check if one/two of them is 'sticky', feel the alloy/steel of each wheel by hand after a steady run of a couple of miles. If one of the wheels is warmer than others, friction from a binding caliper is likely heating it up.

NB:Front wheels will often feel (evenly) warmer than rears because the fronts account for 75% braking.

Getting the wheels off the ground is the best (most definitive) way, however I've used the alternative outlined above successfully a couple of times in the past.

minibreakdown

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  • My Honda: 2005 1.4 dsi cvt
[quote Could it be a seized caliper perhaps?

Really worth checking out.

Short of jacking the car and spinning each wheel by hand to check if one/two of them is 'sticky', feel the alloy/steel of each wheel by hand after a steady run of a couple of miles. If one of the wheels is warmer than others, friction from a binding caliper is likely heating it up.

NB:Front wheels will often feel (evenly) warmer than rears because the fronts account for 75% braking.

Getting the wheels off the ground is the best (most definitive) way, however I've used the alternative outlined above successfully a couple of times in the past.
[/quote]

We have a 2005 1.4 cvt and recently, last month or so, fuel consumption has gone from @53 mpg going down to @44 mpg. I do live in the foothills of the pyrenees, so quite hilly. I thought that the lose of mpg was a combination cooler weather and different journeys. But Thursday last week smelt the rear nearside brake was binding confirmed by a very warm alloy wheel.

Well worth checking.


culzean

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GD has MAP (Manifold Absolute Pressure), and IAT (Intake Air Temperature) sensors,  together these do the same job as MAF (mass Air Flow) sensor would.

Lambda (oxygen sensor) in exhaust can also affect fuel consumption if it goes faulty because it misreads the exhaust gases and can tell ECU to squirt more petrol in.

if EGR is stuck open you would notice bad running at low revs.  If it is stuck closed you may never notice, but it would slightly reduce MPG at higher revs, and engine may run slightly hotter (EGR allows exhaust gas into inlet manifold at higher revs to cool the combustion and reduce NOx emissions). . 
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

hondajazz2003

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Thanks everyone, it seems like I would be able improve fuel efficiency by addressing suggested causes. I will look into the service history and see when spark plugs were replaced. Is it good to get them replaced periodically? I had a full service recently and plugs got cleaned, I think.

To be honest, I have had been filling fuel from an independent petrol station as its cheap and may not have much additives. I will try Premium Petrol /Redex and it may help.

I have serious doubt regarding the binding caliper or something due to wheel. I have noticed little stickiness while driving .It may sound stupid, but wonder if I should test for sticky wheel while driving or just by spinning wheels in resting car. I will check after a short drive for any hotter wheel. About 3 months back, left side front tyre ran over a big deep crack on a A road at the speed of about 50mph.My car survived but other got flat tyres. Though, nothing serious came up in servicing this month. Alignment was out by 3mm and they fixed it.

Secondly, main part of exhaust was changed last year and wondering if Lambda got affected. Could you please suggest how to check that?
Also how to check EGR and air sensor/valve issue? Though, I presume there may not be obvious symptoms to identify Exhaust and EGR related issues.

Oh yes, my car does stalls sometimes and a mechanic said it may be coz it needs more gas. I thought its worth mentioning here as it may hint towards one of the suggested reasons.

Thanks again!
PK

jazzista

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I can vouch for the good effects of a cleaned EGR valve.

HTH,

Stefano

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