I always drive hard, pretty much doing everything that is supposed to be bad for economy, yet I'm constantly getting an average of about 12.5lt/100km. I usually get 10lt/100km when I go to Melbourne, sitting on the speed limit, and around 15lt/100km when towing my camper, including lots of hills.

I actually find that my economy goes up if I have to sit behind slow drivers, looking at what my Scangauge shows. I have this sweet spot that tends to give me best fuel economy around 100-110kmh. Mind you, I'm still tuning, so things keep changing here and there.

 

Some things to consider for all internal combusion engines, compression or spark ignition:
- Higher combustion BMEP (brake mean effective pressure) = increased thermodynamic efficiency
- Friction losses increase exponentially with increasing engine speed
- Aerodynamic and drivetrain friction losses increase exponentially with vehicle speed

So there are two aspects to minimising fuel consumption:
- Maintaining the engine at peak BSFC (brake specific fuel consumption i.e. maximum kWh/kg of fuel)
- Minimising other energy losses (principally friction in the driveline, heat losses, aero drag, rolling friction etc).

Most vehicles are designed such that the aerodynamic and drivetrain losses align with best BSFC when cruising in top gear. Therefore it is usually best to find the speed with the lowest L/100 km in top gear for the best economy. Under load or towing it is probably better to find the lowest L/100 km in the next gear down.

Some other considerations:
- Petrol engines are best driven with minimal revs, 60-80% throttle = minimises the pumping losses incurred by the throttle, but avoids the richer fuel mixtures required at WOT (wide open throttle)
- Avoid braking as practicable as possible
- In manuals, changing gears as low an rpm as practicable

Example petrol engine BSFC map

Ecomodders can be good reading: Fuel Economy, Hypermiling, EcoModding News and Forum - Ecomodder.com Fuel Economy Forum

 

Well from my real world experiences I drive the same as I always have, buying a ute didn't spur me to be a hoon, nor was I not a hoon on my P plates with the wagon (that was always heavier than the ute).

Doing trips on the freeway at 110km/h in my ZD30CRD ute I use about 17.4L/100km in my ZD30DI wagon it was around 11-12L/100km for the same trip. (Healesville to Albury via Hume Hwy).

One thing that I've found interesting is fuel varied by load and terrain more in the ZD30DI going up to about 15L/100km when loaded and being driven hard around the mountains and as little as 9.5L/100km when not exceeding 80km/h whilst driving around the Yarra Valley. The CRD has got as little as 16L/100km doing similar driving, but when loaded, fuel usage only differs by .XXL/100km.

 

There is another school of thought that that goes along the lines of there being only a limited supply of fossil fuel left on the planet so If you don't use your share somebody else will .
this then dictates that you should drive it like you stole it and when It's all gone we will modify push bikes or electric something's
And there is only one thing worse than sitting behind someone doing 10 km below the speed limit so they save fuel and that's being behind someone sitting 5 kmh below the speed limit
Yes I agree with sitting in the cars sweet spot but just don't go so slow that all you do is annoy others .

 

My best ever eco was a work trip to Kempsey from the Sunny Coast around 3 years ago doing my 102/3k thing and I achieved 8.8L/100, on that trip I was quite conservative and max boost at the time was 16psi.

My next best was coming back from a meetup with Chaz, Dronus, RumCaj and the SA boys about 2 years ago where I achieved a 9.6L/100k with 18psi boost and I was not being conservative just driving normal, since then I have upped the fuel intake with the JayCar unit which has seen me settle into the low 10's.

Scottmiester has hit the nail, I have known for a long time that when I get lazy and leave it in 5th knowing I'm a bit under, but it has enough torque to get away with it, my eco goes up, but when I consciously match the gear to the terrain it gets much better.

So basically I could tune mine to 9's if I wanted to.

 

I also tend to drive in a 'spirited' fashion, as it keeps my brain, reflexes etc active and exercised, and it keeps me attuned to the Patrol and how it's going in terms of suspension, brakes etc. I don't care about getting older, but I would hate the idea of getting 'old'. And that ensures that I get the best out of the Patrol, to get back on topic.

 

I'm not sure spiritedly comes into it all that much now when touring on highways, to drive from the Sunny Coast down, your sitting on wide multilaned highways, driving spiritedly in that situation would probably require you to be weaving in and out of traffic at 120k .

I often hit "find alternative" to drive on back roads, a November trip to Kempsey hitting find alternative saw me sitting on the speed limits all the way through the mountains to Coffs and still come home with high 10's.

I fully agree driving spiritedly has it's benefits, but there is "driving spiritedly" and there is "driving spiritedly" as you well know.

 

Here is the data off my phone for my ute

The 19.9 was playing around with the dawes/needle and MAF housing.

 

How big is your fuel tank? Your first reading, for example, indicates a 139lt of fuel, the second 141lt, the fourth 146lt, the second last 150lt and the last one 135lt.

 

Whoa....... It may be time to burn it .

 

I would certainly get rid of it with those figures.
I can get that towing 3200Kg van.

 

Maybe he needs to burn the phone .

 

The utes are 180L tanks. The sub is much bigger.

 

You have a 180lt main tank and the sub is even bigger? No wonder your fuel economy is crap.

 

'98 2.8L, 33's, Running 15psi boost til recently.

Around town, it doesn't make too much of a difference my driving style, maybe 0.5L / 100.
However on a recent trip to Northampton for the dirt drags, travelling up, cool ambient temperature, a/c off, minimal overtaking, sitting on 100-105kph I averaged mid to high 13's/100km - even with 70k towing a 2T trailer.

The drive home I was following my brother and we got a bit excited, sitting between 105 & 115kph with a lot of overtaking and air con running, 16L/100km

Needless to say I'm now quite happy to plod along at 100 - 105kph on the open road

 

Just finished a 3000k mostly highway trip, on the way down I averaged 10.8LPH, that was sitting on the speed limit where I could but a fair bit of it was at 90 because of the horrendous amount of Christmas traffic on the road.
Coming back up with less traffic on the road and cruising at 110 most of the way, lots of overtaking, booting it up hills to maintain speed, etc . I averaged 12.5 LPH
That was loaded up in the wagon and roof rack piled up with stuff both ways.

 

89 TD42 12psi running 33s

I did a trip across the country recently and took the opportunity to see how speed affected economy. Fully loaded with gear, rooftop tent and 2 jerry cans of diesel meant it was as heavy as it was going to get.
110km/h = 18L/100km.
100km/h = 13.5L/100km
90km/h = 11-12L/100km

Doesn't seem to matter how much 4x4 or city driving I do, those numbers are pretty consistent. So I don't go above 100km/h and I usually sit on 90km/h, unless I'm in a hurry. Not that 10km/h actually makes much difference time wise... Difference between 90 and 100 is a grand total of 4min/100km. I'll take better economy over saving a couple of minutes.

 

I agree, similar for mine, once I hit 110K it's like standing under a cold shower tearing up $50 notes, every k under is worth a few bucks.

 

lol. Me no speek engrish good

 

How the hell do you guys manage to get such good economy?
04 St with 33's auto. Dawes set to 16psi or so max. 100km cruise is at about 8psi od and Tc locked.
Round town I'm getting 16l/100. I haven't been on a long enough drive to test highway.
Boost goes to about 8-9psi on accel from lights always with less then 30% throttle. Alloy bar, no winch, but outback draw setup.
How can I get it lower? Even just 13's round town I would be happy with

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Don't forget you have 33's, do you have a lift and a roof rack? My 2000 (and before anybody asks my eco numbers take into account tyre/odometer error). I have a 3" lift so I will never get back to some of the old eco numbers. I also have Outback draw setup and my truck at it's lightest is 2.8T.

So I believe it is possible for you to achieve better with a DI with a bit more work and study .

 

Thanks for the reply geeyoutwo

33's make my speedo/odo almost perfect vs a Gps..
Yes to the lift, 2inch. No to the roof rack.

Study? Can you point me in the right direction for what to look for?
I know more boost = more fuel. And I know the auto will use more then a manual.
Would haveing a dual Dawes setup help?
I don't think the Tc lock up mod would help too much round town.
My wheel alignment and bearings and such are being done today.
Tire pressures aren't ever low.

I can't really think of anything other then dialing back the fuel (jaycar maf mod/lower boost) that would help.

What sort of throttle/boost reading do you get when driving off from lights and such?

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What you need to do is ensure reasonably correct air/fuel ratios. It's not a big issue if you increase boost and add more fuel, as you'll get more power and thus need less throttle, so overall will use less fuel. But this needs to happen across the load/rev range and not just at the top end.

 

Yeah that's what I thought (more boost/fuel but more power = less throttle)
So what's the best way to get the afr's right Ray?

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Not quite the whole story, what we are talking about is energy efficiency, so more power does not always translate to better fuel eco, you must also factor in torque and no they don't always go hand in hand. One question, do you still have the std exhaust? my 2 3/4" made a world of difference to the efficiency of my DI engine in both outright Hp and Torque.

One of my challenges was to get the most torque I could rather than just sheer Hp and I'm happy with what I have, torque range being in the right place will give far better eco than just having lots of Hp.

Sure the dual Dawes will help and it only costs for another Dawes and a solenoid valve, I just don't use mine as often as I should around town, that's where the real benefits are. My 100k cruise on flat road is done at 9.5psi, 3.60-3.63v MAF and 18% TPS.

I have spent a lot of time playing with spoolup rates and at the moment I'm quite high but still experimenting with my JayCar as well (being one of the first to use them means there was a lot of early experimenting with all these factors), I've upped the top end a few months ago with good results but I don't spend much time there, I rarely ever go past 3 grand unless I'm towing and then 3500 will usually see me through. For me the hardest part about doing the JayCar was getting around my 2 limp zones and still up the fuel to get better torque, this meant I had to narrow the ranges of adjustment quite severely and that took a lot of mucking around to achieve, funnily the recent fitting of a K&N replacement air filter seems to have improved performance at 2000 but has just tipped me over the edge of MAFv for the low limp zone .

Depending on what you have, basically to change AFR you need a chip and a dyno or your JayCar unit and a dyno. There are other ways but they are the most effective.

Give us a list of all the mods you have.

 

Long term country/city (inner Melbourne) is 13.3

Best on freeway average at 100 is 10.9

Towing 1.6t is 14-15

Gentle starts and finishes. Cruise almost all the time on highway except long hills. Use the gears for braking when the camper is on and when steep without. Anticipate the hills.

2010 Ti CRD auto with BFG AT, roof bars, alloy bullbar. Tunit chip.

The 13.3 becomes 13.5 when my wife has been driving the Patrol. The other car is a Honda Jazz.

 

Just did a run from Hervey Bay to Alstonville via Ipswich through Brisy over the Storey Bridge. Was running late for an appointment. 13.7l/100km. Not bad for 6.5L 2" lift, roof rack bullbar and winch.

 

LOL I'd want better than that after spending $30K on an engine conversion. I'll keep my 17L/100km thanks. It's cheaper

 

Don't know where you get $30k from. This is better than the 3l that was in it and it tows better and is great in sand and steep country.

 

Yeah, ya knob! It costs at least $40,000.