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Poor Fuel Consumption on 2.4 Auto

danny35

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Accord 2.4 Auto
Hi all! Well I was hoping not to have to make a thread like this, but I need some advice on poor fuel consumption. I bought a 2004 82,000 mile 2.4 Automatic 3 weeks ago and have been experiencing very bad fuel consumption figures. This is despite a fulls service having been carried out and me driving in semi-grandpa mode. This was one of my biggest concerns before buying and I would really aperreciate some advice.

1st Fill up - £30 - 90 Miles so @ 99p per litre = 6.66 Gallons = 13.6 MPG

Some of this mileage was before the service and I ***ume that the car was left running throughout the service. Also most of the driving was also in bad traffic

2nd Fill up - £30 - 120 miles - 120 miles @ £1.06 per litre = 6.22 gallons = 19.29 MPG

This was particularly worrying as this was after the service where air/pollen/fuel filters were changed e.t.c, and without much traffic at all and 40% motorway or dual carriageway driving.



I measured the MPG by zeroing the mileage when the petrol light came on,then filling up with £30 of petrol and waiting until the petrol light came on to measure the MPG.

I have been reading up and have the following ideas of what to check:

- Clean MAF sensor & EGR
- Calipers (though I think they should have been checked already)
- UN-metred air in the system
- 02 Sensor
- Clean throttle body/sensor
- Wheel Allignment
- Tune up
- Pipes for damage
- Air filter connection hoses.

I put a bottle of cataclean to clean fuel injectors so will see if that makes any difference.


Unfortunately, I am not very mechanically minded so would have to get a mechanic to perform any of the above. Are these the correct things to check and have I missed anything important?
 
Hi John, do I need to fill the tank up all the way for it to be accurate? I didn't think it would make a difference as I would still zero the mileage meter when the petrol light coming on, then fill up petrol and then calculate the MPG when the petrol light comes on again.

My second and most recent reading of just under 20 MPG worries me as the just car has just been serviced and the tyres, filters and fluids are now at their optimum level so things can only get worse. What also concerns me is that this 20 MPG reading has been with driving with not a lot of traffic and about 40-50 miles of motorway/dual carriageway mileage included. I am also and driving carefully and accelerating slower than I would normally do so.

I do usually do a lot of short journeys generally which I know isn't ideal but there is surely no way that I should get 20 MPG from little traffic and 40% motorway/carriageway mileage just after a service?

Also, what do you mean by odometer and not the computer?
 
you need to:

-brim the tank
-drive around (you don't have to empty it completely)
-brim the tank again

This will tell you how much fuel you used for the distance travelled.

Then, Miles covered, divided by litres used, x 4.55 will give you your accurate mpg.

Just ***uming the light comes on at the same point will never tell you the truth.

I've not owned the same car as you have, but I'd expect low twenties round town, and low 30's on the motorway.
 
Goodluckmonkey said:
you need to:

-brim the tank
-drive around (you don't have to empty it completely)
-brim the tank again

This will tell you how much fuel you used for the distance travelled.

Then, Miles covered, divided by litres used, x 4.55 will give you your accurate mpg.

Just ***uming the light comes on at the same point will never tell you the truth.

I've not owned the same car as you have, but I'd expect low twenties round town, and low 30's on the motorway.
So when do I refill the tank, when the petrol light comes on, or when the odometer reaches the red empty line?

Just out of curiosity, why is necessary to have to fill the tank twice to get the MPG. Surely if you are measuring until the odemeter reaches Zero, it would be irrelevant how much you fill up to? I know that I am most likely incorrect though :)

If I am doing purely town mileage with traffic then I would be okay with 20mpg but with little traffic and 40% motorway miles, it is just too low.
 
You refill the tank whenever you like.

The fact that you fill to the top of the tank provides a constant level before and after, ie - at both times the tank has the same amount of fuel in it.

This means that if you measure the mileage between the two fills you know the miles covered.
The amount of fuel you add on the second fill is the amount used.

----------------------------------------------------------------

The Subaru Legacy I just sold averaged 25mpg over 80k miles.
The car's the same weight, size, shape and of similar drag coefficient to my accord estate.
There were more transmission losses through the 4wd system than you'd have with a 2wd car, and the 3.0 petrol made 270hp.

Using that as a yardstick, your 2.4, even with an auto should do at least the 25mpg that did.
 
What I normally do is just wait for the fuel light to come one, reset the miles covered trip thingy, fill up £10 or £20. When fuel light comes on again I know how many miles I've done on £10

With 2.4 manual saloon I average 50 miles/£10 with Shell nitro+
 
The odometer can be reset with the button sticking out of the speedometer, the one that regulates your dash lights, just fill up and before you move off push and hold it in the reading will reset to zero, Nothing to do with petrol gauge or computer, just reads "trip" milage, it has two trips A and B.

To really see if you are running rich take a spark plug out, the tip should be a nice light brown in colour, if rich it will be black/wet, if weak it will be white/chalky.
 
vaynah said:
What I normally do is just wait for the fuel light to come one, reset the miles covered trip thingy, fill up £10 or £20. When fuel light comes on again I know how many miles I've done on £10

With 2.4 manual saloon I average 50 miles/£10 with Shell nitro+
Thats no good! some tenners get you further than others, tesco versus Shell optimum comes to mind.
 
edgeoftime said:
Thats no good! some tenners get you further than others, tesco versus Shell optimum comes to mind.
True, but it gives you a good average still
 
Okay, so I guess I will have to fill up the tank. I will get back when I have the results.
 
I just noticed that my steering wheel seems to veer itself, particularly when doing sharp turns or turning left. So if I turn left for example there seems to be slight pressure momentarily of the wheel to the right, and sometimes when going straight it veers slightly to the left. Do you think it may be a wheel alignment problem?
 
Can anyone recommend a good reliable place/company in Londonto get my wheels aligned?
 
Could be, or a worn suspension component somewhere.

Wouldn't account for being 15mpg shy of where you'd expect to be though.
 
Would that kind of thing not have been checked on the pre vehicle inspection and/or the service though?
 
As mentioned by several people already, the only way to measure mpg properly is by filling the fuel tank until the handle on the pump clicks off, then zeroing the trip meter before leaving the filling station.

Then drive the car until the tank is close to the empty light (whether the light comes on or not), go back to the same pump and refill until the handle on the pump clicks off.

Now go and pay and ask for the receipt. Work out the mpg from the miles on the trip meter, and the amount of fuel on the receipt.

Reason for doing it this way is because it gives a more reliable average i.e. more fuel over more miles. You can even do it several times i.e. write the miles onto the receipt that were on the trip meter, then reset the trip meter, etc, etc.

Also, the heavier an engine is, the more thermal mass it has, so it takes longer for the entire thermal mass to reach full temperature, and until that happens, the engine has not reached max efficiency. So if you drive a 2.4 Accord to a supermarket that is only 2 miles away, and then drive back home, your mpg will be appalling for that single trip. But combine it with a 1-hour motorway drive on cruise at 70mph, and the combined mpg will be vastly improved.

Tyre pressures also make a difference.

Finally, the tracking on the saloon needs a 4-wheel alignment, the Tourer does not.

edit: and this time of year the mpg is worse on all cars in the northern hemisphere
 
Thanks Brian! I did fill up my tank up yesterday and will be back with the results which will probably be in around 2 weeks. I do make a lot of short journeys normally like you mention so that is not ideal, however my last tank was terrible considering I did mainly longer journeys that included motorway/dual carriageways, but I understand that the measurements were probably not very accurate.

I plan to take the car in to a wheel alignment place, possibly today but am worried that he may carry out the alignment, even if it doesn't need to be done.
 
it's called a "Hunter 4 wheel alignment", if they don't have it, find somewhere that does (Google)

don't know the difference in price between a check and an alteration, I presume that there is (my car is a Tourer so it only needs 2 wheel alignment, although I think that a limited amount of 4 wheel alignment is possible on the Tourer)
 
Rear LCA inner bolts are cam type on a tourer, so you have a very small amount of combined camber and toe adjustment.

It's a very simplistic radius arm setup though on the tourer. My legacy wagon had a lateral link setup similar to the accord saloons. The main benefit of that setup is it cambers in with compression and is normally designed to passively rear wheel steer a little through bush flex.

Whilst archaic, the tourer setup does allow for more rear load space, and that's what we want in a tourer.
 
Use a mpg app on your phone, takes all the maths out of it and you have a permanent log of fuel used/cost/miles travelled etc...
 
Kris81 said:
Use a mpg app on your phone, takes all the maths out of it and you have a permanent log of fuel used/cost/miles travelled etc...

^ not a bad idea, but tbh since all phones have calculators, the maths is astoundingly simple

mpg = miles-on-trip-meter ÷ litres-on-receipt x 4.54

e.g. 388 miles on trip meter, 48.39 litres

mpg = 388 ÷ 48.39 x 4.54 = 36.4


edit: there's also a revolutionary device called a "pencil", which can be used to "write" numbers onto the receipt :eek:
 
^ note also that mpg done this way is only as accurate as the speedometer, and most speedometers read about 5% fast, so the "decimal" in the mpg is not really relevant

but it is more accurate than most on-board ECU methods
 
To be fair, the two occasions I've run dash command throughout the consumption of a whole tank of diesel, I've got exactly the same result as the old fashioned method. (Measured to one decimal place)

Pretty surprised to be honest, I was expecting a huge discrepancy.

On my last car, power and torque figures (on a 4th gear pull) were within 1% too once it had all the information. (Gear ratios, weight, drag coefficient, frontal area etc.)

I'm a huge sceptic when it comes to the accuracy of such gadgets, especially phone based ones.

I still believe it's an accumulation of errors making it right, but it does keep proving me wrong, so who knows?

The economy numbers from manufacturers onboard displays on the other hand, are always pish.
 
My worse mpg has been 20.2 with all town driving. The best I've had is 29.7, which was alot of motorway and A roads. These cars will never return good mpg but yours does sound bad so something could be up.

Have you used the right grade oil and checked tyre pressures?
 
-Rich- said:
My worse mpg has been 20.2 with all town driving. The best I've had is 29.7, which was alot of motorway and A roads. These cars will never return good mpg but yours does sound bad so something could be up.

Have you used the right grade oil and checked tyre pressures?
My mechanic used Castrol 5w40, and the tyre pressures have been checked 3 times since I purchased the car (pre vehicle inspection, service, free honda car check) and is apparently perfect.
 
I believe the recommended grade is 5w30, that's what I've used for the last 2 years. You could try changing it and see if that helps. Have the plugs been changed?
 
-Rich- said:
I believe the recommended grade is 5w30, that's what I've used for the last 2 years. You could try changing it and see if that helps. Have the plugs been changed?
I did originally want 5w30 but when I went for the service they only had 5w40 or 10w40, so I opted for the 5w40. Do you think the oil would make that much of a difference to the fuel consumption though to make it worthwhile to drain and refill the the oil again? It would be quite costly I ***ume, so only would consider changing it if it makes a noticeable difference.
 
Hi all, just a quick update. I am now on half a tank from filling up and am currently on 115 miles. I have done town driving albeit with very little traffic and with a much lighter right foot than normal. On the ***umption that the first half of the tank is always higher than the remaining half, I will be lucky to hit 200 miles until the light comes on. Although just an estimation, I think it will be near the mark. If so,then I will be a bit disappointed considering I have been driving with a much lighter right foot than normal and have been as traffic free as I am ever likely to be.
 
danny35 said:
I did originally want 5w30 but when I went for the service they only had 5w40 or 10w40, so I opted for the 5w40. Do you think the oil would make that much of a difference to the fuel consumption though to make it worthwhile to drain and refill the the oil again? It would be quite costly I ***ume, so only would consider changing it if it makes a noticeable difference.
yeah I doubt if the oil grade will affect mpg to such a large extent

danny35 said:
Hi all, just a quick update. I am now on half a tank from filling up and am currently on 115 miles. I have done town driving albeit with very little traffic and with a much lighter right foot than normal. On the ***umption that the first half of the tank is always higher than the remaining half, I will be lucky to hit 200 miles until the light comes on. Although just an estimation, I think it will be near the mark. If so,then I will be a bit disappointed considering I have been driving with a much lighter right foot than normal and have been as traffic free as I am ever likely to be.
at this time of year, mpg is always worse, especially on short journeys. Even though the weather is relatively mild for this time of year, if all your journeys are short and the engine goes cold between each journey, then I reckon 20 mpg is about right (would be 25 mpg in the summer)
 
freddofrog said:
yeah I doubt if the oil grade will affect mpg to such a large extent


at this time of year, mpg is always worse, especially on short journeys. Even though the weather is relatively mild for this time of year, if all your journeys are short and the engine goes cold between each journey, then I reckon 20 mpg is about right (would be 25 mpg in the summer)
Thanks for the reply. I wouldn't mind 20mpg so much, but it includes me driving with a light foot and with minimal traffic. I dread to think of the MPG when I drive more spiritedly and get caught in normal traffic. I was hoping for 25mpg on this tank and 20mpg driving more spiritedly with normal traffic.
 
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