bad fuel economy

Ive just been looking through a few fuel economy threads. Seen a few people being disappointed with fuel economy I can only dream of.

Usually in city driving I will get 430ks out of a full tank, the most ive managed is 540ks out of a full tank(2005 d22) which was driving as gently as possible on the freeway/highway.

When I bought the car it had 110000ks on the clock and I added a few extras as soon as I bought it so I have no idea what the original fuel economy was like. Anyway, now it has 190000ks on it ,alloy bullbar,snorkel,fridge duel batteries, bigger mud terrains, canopy, arb trade rack and lots of other little things bolted on here and there. Im just wondering if this is the type of economy I should expect? Also the car is serviced ever 10000ks and I use fuel injector cleaner all the time.

430km to 80 litres is 18 LPHK (litres per hundred kilometres). That's not good for a relatively unladen vehicle.

540km is better - closer to 15 LPHK - but it's still not good.

First, I'd be filling the tank, reset the trip meter, and every fill after that, write the trip meter info on the fuel docket so you can see exactly how many litres you used for that distance.

There is a problem with this calculation though - your tyres. We need to adjust the distance traveled as displayed by your car to compensate for the different road size of tyre.

Basically, a larger tyre will cover more ground in a single revolution than a smaller tyre. This does two things: first, it makes it harder for the engine to turn that wheel over (longer lever) and second, it makes the odometer read LESS km than actually traveled.

You may be getting 560km instead of 540 (14LPHK instead of 15LPHK).

To get this correct (and post it here so it can help others who want to figure this out too), I'd do the following:

Head to a freeway, where they have those "Odometer length check" areas and stop at the start sign. Write down your trip meter value and reset your trip meter.

Stop at the exact same distance from the end sign and note your trip meter value. Bring that figure back to us here and we'll work out the error, and give you an idea of how many km you're REALLY getting.

Only then will we get a more accurate idea of how your fuel economy really is.

Alternatively for those people that don't have those highway check points (because Sydney/NSW is about the only place I've really seen them) get a GPS and do the same thing. Your GPS reading should be accurate enough to give you true speed (match this against your speedo reading) and distance traveled (match this against your Odo reading), then work out the difference,

However from other threads on this forum people have discussed that Odo's and speedo's aren't always out together or out by the same amount so it does pay to get each reading if you want some degree of accuracy.

Thanks for the suggestions, with my gps this morning my dash speed is reading 6kph lower when travelling at 100kph. I know this will add a little to my economy but not very much. Also, Im fairly sure the tank in my nav is only 70ltr so that makes it worse again. I should also have said that 90% of the time I have 400kg of tools in the back. I still though I would get better economy but maybe this is all I should expect? Thanks.

You possibly could get better economy but one thing it pays to remember is that there is no magical figure, there is suggested figures and there is calculated figures but we are all going to vary and vary quite a bit going by threads like this. Adding 400kgs and big tyres etc are all going to have some bearing on your figures but as too how much it's once again not a magical figure.

You're right the 6k difference isn't going to change your calculated figures that much but if your odo is out by the same degrees over 500 ks (that you quoted above) 6 ks in every hundred is still 30ks per tank. I also believe the D22 tank is 70 as you say, going by other threads on this forum.

I have done some quick calc's whilst driving (using scanguage) and i reckon i'm about 2 litres per 100 worse off when i run 32" muddies, compared to 31" AT's.

Unless your going off-road every weekend, i would suggest investing in a 2nd set of rims and tyres (of course, budget permitting ...). Keep one set for the road and daily use (factory spec diameter) - and use the muddies (large diameter if you like) only for off-road trips.

On my D40, i have also found that keeping to a max of 95km/hr on highways use's less fuel than pushing upto 100km/hr. Pity i cant drive that slow though, because i alway set the cruise control for 100k's on the knocker. Except for the Hume hwy - 110k's all the way where possible.

So my fuel figures when travelling insterstate with the camper trailer (31" tyres) is a shocking 17.5 l/h (approx)

And my normal figures around town are anywhere between 11.5 to 14.5 l/h depending on how i drive, loads, tyres, higway vrs suburban street - etc.

If I'm being pedantic about fuel and really trying to get decent economy figures I've found that traveling between Melbourne and home I'm better setting my CC at 95-96 kph between the burbs and Pakenham, then increasing the speed to about 100- 103 kph from Pakenham to Warragul and then dropping it back to 95-96 after Warragul.

The reason for it is obvious to those who know the road, from Pakenham to Warragul the road rises pretty much all the way and making George drive that few kph faster means no gear changes going up hills. At times it doesn't appear like that is the fuel miser method because your actually going faster but it does work because you don't use as much fuel for that period of time maintaining a constant speed when at the lower speed the CC changes gears and kicks the revs up to anything over 3000 RPM when it labours on a hill because it's not clever enough to see two hills one after the other.

Of course if I was extra pedantic about it I wouldn't let George drive at all because I can drive much more economical than he does, but laziness outweighs economy every time on long trips.

No-one has suggested it yet, so it may not apply, but would the reset process be worth considering?

The reset procedure is not a definite solution. It can work and plenty of people here have reported improvements after doing it, but there are also people like myself that have done it and seen no improvements.

The procedure shouldn't harm anything and no one here has reported any adverse effects so it's an option but not something I often consider given that in so many cases economy problems come down to driving habits more than ECU resets.

Has your cat collapsed ?

Got much power ?

Dave.

I think the ECU reset is worth a try, but make sure you make room on the shelf for those tools first. Empty vehicle and a gentle drive at moderate highway speed is what's needed for the learning to be economical.

That process is:

1) Unload the vehicle, write down your trip meter values
2) Disconnect the NEGATIVE (black) lead from the battery
3) Depress the brake pedal for 5 seconds OR turn on the ignition for 5 seconds
4) Release the brake OR turn off the ignition
5) Reconnect the battery lead and ensure it is tight
6) Take the vehicle for a gentle drive (about 10 minutes ought to be enough), don't rev it over 2,500rpm. Try to use less than half throttle the whole time.
7) Turn the ignition OFF. Your fuel settings are now saved.

Just on the speedo/odo issue - the speedo and odo get their data from the ECU, but the speedo reads poorly because the needle itself is inaccurate. The odo is very accurate. With larger tyres, the odo will be reading fewer km than are actually travelled. If you can give me the current tyre size off the sidewall, I can work out how much your odo SHOULD be out and that might give you a pleasant surprise with economy figures.

l'v got02 ute with 220,000 km on it and l am averaging 10 lt/ 100 km with @200kg of tools in back for work. mainly hwy driving and just did trip with pop top van 1.3 tonne plus work tools on ute and two fat dogs and got around 13lt / 100 km on average western country

Not sure about the cat but power is the same as its always been. Ive never had very good economy with the car.
I dont have the funds for 2sets of rims at the moment so I will just wait till the mud terrains wear out and throw some all terains on, should help a bit .

Off topic, I just fitted a aftermarket digital temp gauge. Sits at around 85 degrees all the time once hot, is this the norm with navs? also fitted oil pressure gauge but have not finished hooking it up yet, whats the norm digital reading for that? Thanks

Woody, interesting you say that. When I had my D40, I used to get my best fuel economy cruising at about 120-125kmh (GPS speed) between brisbane & the gold coast. The setup was a little different to most though, I had a V6 auto with 305/35/R24 low profile road tyres, which were about 2-3" larger in diameter to the standard 16" tyres. I found that below 100 the auto tranny would often switch between 4th and 5th on slight terrain rises, which negatively impacted economy.

All in all though, the economy was rubbish. I was getting averages of between 15-20L/100km. 350km from an 80l tank (if 100% city driving)

Lucky my work paid for my fuel huh!

gadgets said:

Not sure about the cat but power is the same as its always been. Ive never had very good economy with the car.
I dont have the funds for 2sets of rims at the moment so I will just wait till the mud terrains wear out and throw some all terains on, should help a bit .

Off topic, I just fitted a aftermarket digital temp gauge. Sits at around 85 degrees all the time once hot, is this the norm with navs? also fitted oil pressure gauge but have not finished hooking it up yet, whats the norm digital reading for that? Thanks

Click to expand...

If you don't have the funds for new rims don't sweat too much yet, just get me the tyre size info and I'll work out your actual LPHK and odometer error for you.

Your coolant should be sitting around the 95-100C mark. The thermostat should be opening at about 80-83C and should be fully open at 95C. At 98C the cooling fan will be brought on at low speed (unless you exceed 40km/h) and at 105C the ECM will bring the cooling fan up to high speed (unless you exceed 80km/h). These figures are for when the air conditioning is OFF. When on, the fan runs all the time (EC.PDF p1120).

On the way home from the big smoke this arvo...these liquid lunches with Woody are becoming hard to knock back...the outside temp varied between 31 and 34 and the hottest temp my scangauge read was 93 with it dropping as low as 91 every now and again. Even in 45 degree heat in Renmark last year the temp got no higher than 95, but each car will be different, however I've only ever seen under 90 (after the engine is warm) in temps of less than 10 degrees, and damp thick fog and even then I think it only went as low as 87.

mines the same as yours, done injectors, timing chain, intercooler, hi flow turbo and air box and still shite economy! lucky to get 500ks per tank! and that's with out the camper trailer ..

Does it blow any smoke?

I had a dud injector that was pushing my fuel economy up. Once they were replaced it improved by about 2l/100km. Getting rid of the Bighorns for BFG ATs didn't really make much difference to economy (it improved comfort though!).

I get about 10L/100km when cruising at 100km/h, and about 12 when at 110. This is with steel bullbar, winch, 2" lift, canopy and usually just luggage/baby stuff in the back.

Don't do any city driving, so I couldn't tell you what it does there...

My 2012 D40 gets about 9.2 combined driving standed though atm only got 265/70R17 maxxis bravo at 980s

Hmmm I was thinking faulty injector, they would be lucky to be 10'000 k's old and I always use injector cleaner also. danm this never stops!