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  1. #1
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    Default Fuel consumption calculation for overlanding (planning stages)

    Hi all,

    Fuel consumption is a great topic around any camp fire. I, personally, can never match manufacturer claims or for that matter claims from other owners of similar vehicles. I do keep an accurate record of my personal fuel consumption via an app so have a base figure, lets call it 10km/l. What I would like to know is based on what you achieve day to day, what do you add to or subtract (%)from you every day consumption when calculating fuel or an overland trip. I really want to do Kgalagadi so consider that terrain for 4x4 use. I've never been so have no base information to work from so far as how much High range/low range or normal driving will need to be done.

    Any input would be most appreciated.

    Thanks in advance
    Craig

  2. #2
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    Hi Craig,

    Manufactures claims are very much an ideal scenario case and its rare that we actually get that especially if your commute involves hills of a series of traffic lights

    In terms of overlanding consumption there are two main areas where consumption will increase, but they differ.

    I find on road that my consumption increases by around 2L/100km if I keep between 100-130kph (so anywhere between 11-13L/100km). This is mostly related to aerodynamic drag due to roof-racks and jerry's etc so it goes up more if a strong headwind occurs.

    In general, I find on the gravel sections of the Kgalagadi I get anywhere between 12-14L/100km fully loaded with gear.

    Then in the sandy sections like on the way to Mabua from Nossob consumption goes up to 15-16L/100km. I only used low range on the steep climbs to avoid unnecessarily damaging the road.

    We did nearly 900km from Nossob-Mabua-Kaa-Nossob (all sandy) in 2019 in a 3.2 DID Pajero LWB (120kw) and a D4D Hilux and we used around 130L of diesel. The cars never worked hard but it was very hot and there were some sandy sections. Consumption will go up a lot of towing. I'd work on 17L/100km towing there.

    I've travelled a fair bit with a 3.2 ranger in our convoy and its similar to the D4D hilux at around 1.5L/100km lighter than the Pajero in most places.

    On general on our trips we estimate our fuel costs on worst case scenario so we work on 15L-100km. This usually allows an accurate upper estimation of fuel costs for the distance.

    **I must add that we are by no means consumption conscious, its not nice worrying about fuel when you are on holiday and in that same breath, If we know fuel may be scarce we always top up at the last spot and take a little extra.

    Enjoy, its a wonderful place.
    Last edited by ChasingSunsets; 2021/05/03 at 11:50 AM.

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  4. #3
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    Both my vehicles use more fuel every day than on a trip (Jimny is about 10l/100km every day vs 8.0l/100km on a trip. The Defender is about 11l/100km every day and on a trip it gets 10.3L/100km). So I take my daily consumption figure add an extra l/100km on top of this and then calculate the estimated consumption based on estimated distance to be travelled. Add an extra full tank of fuel to this and I have my fuel budget. This method works well as my consumption always is lower than expected and I have a spare tank left over in case of emergency.
    I also add a rand or R2 to the current fuel price when calculating. This method allows for unexpected exploring etc and I've always returned home with a surplus from my fuel budget.
    2018 Suzuki Jimny - Expedition vehicle
    2002 Land Rover Defender - Daily Drive

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  6. #4
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    The answer is the same as to the question, how long is a piece of string?
    Depends entirely on the terrain. If you are slogging through deep sand or mud in low range, all on-road, gravel, or high range averages go out the window.
    Tony Weaver

    1991 Land Rover 110 Hi-Line S/W 3.5l V8 carburettor
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    Previously Land Rover 1968 SII, 1969 SIIA, 1973 SIII, 1983 Toyota HiLux 2litre, 2006 Land Rover Freelander TD4 HSE.

  7. #5
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    Not an expert but i would do two scenarios. Fill up tank full then Find a difficult terrain and drive that in 4x4 for a few hrs then take milage and fill up... Dividing fuel into milage to get a guide line. Then take full tank onto a long road for a few kilometers, then fill up and calculate. Imho you will have two different scenarios. So if open rd gets 12km/l then work on 10km/l. If off road gives 10km/l then work on 8 or 7 km/l... Work out cost of fuel by adding R2 to R3 extra on current pricing. Sounds silly but you could hit a head on wind.
    Isuzu STD 2.5d 2x4 rear diffy lock
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  8. #6
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    Not just the camp fire, this also goes around inside my head when planning trips. The reason being that I have a very thirsty 3.8L petrol engine in Pajtu.

    I have over the years tried to nail down the worst consumption that I have seen when towing, that was around 20L per 100km. So that is my baseline calculation for volume for distance..
    Stranger

    Lusted for a Landy but the Pajero was sexier and bigger in the right departments, just like my Missus.

    2004 Gen 3. 3.8i petrol V6 (PAJTU)
    X Factor Bundutop trailer (designed by me)
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  10. #7
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    When I first started wandering into areas where fuel range and reserve were critical I recall learning that you never pass the point at which you've used half of your fuel unless you know for sure that you'll reach a source of fuel, and that you should take into account a reserve (in my case usually 100 Km, depending upon whether you expect conditions to deteriorate and/or fuel consumption to increase).

    We track fuel consumption continually, and notice variation with load, cruising speed, surface, and country (Venezuelan fuel is terrible and consumption increases).

    So, for predicting consumption - we find that we can get as little as 15 L/100 Km - steady 80 Km/h cruise on the flat (Nullarbor for example), however at home (most mountainous country in the Americas) we get around 17L/100 Km, and if we're fully loaded (5 people with kit east to west or the reverse) we get anything up to 20L/100 Km (north to south more like 18 L/100 Km.

    An example from our Australian trip:

    We used our Montero 3.8 L petrol (it's becoming difficult to have a diesel in much of the world today). Because this engine is not sold now in Australia, and because few people seem to use this model (equivalent to a Pajero) in Australia, we found it tough to get insight into the probable fuel consumption. Experience in deserts elsewhere in the world led us to conclude that we would need to plan on 25-50% higher consumption than on tarmac. We saw advice online ranging from 50-100% higher consumption. At Mount Dare the advice was to plan on 50% higher than "normal" and to plan on the possibility of taking the longest route (770 Km), since the shortest route was badly chopped up when we were crossing.

    So, we calculated needing around 195 L of petrol. The tank holds 88 L, and we had cans for another 100 L, so we bought one more and left Mount Dare with 208 L. We ended up finding that the French Line wasn't as bad as we had expected, and ended up on the French Line, Rig Road, WAA line, Knoll's Track, French Line, and then QAA line. 610 Km in all. We filled from cans once and when we arrived in Birdsville found that we had used 135 L, so a lot less than we thought we might need. We hope that this information helps anyone planning on using the same vehicle (petrol engine).

    Beautiful trip - one other vehicle each day on the first 4 days, then a lot more traffic from Eyre Creek westwards. No problems at all with the vehicle. Crossed "Big Red" easily (not by the most aggressive track since we didn't see much point in stressing the vehicle before the next 20,000 Km or so of our trip). Fantastic starry skies and overall a great experience.

    The overall trip is at www.discoverthedreaming.blogspot.com

  11. #8
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    Thanks for the top tips guys, much appreciated, it gives me some real world scenarios to consider. That's exactly the kind of information I was looking for. While we are busy with the research for our maiden overland trip, hopefully 2022 will be the year, my greatest anxiety is the fuel consideration. We are campers not overlanders so this is completely new territory for us. I would like to to do a short 4-5 day trip and then slowly increase our range to fully fledged 2-3 week trips. That's my dream...

  12. #9
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    Quote Originally Posted by Craig Van der Poll View Post
    Thanks for the top tips guys, much appreciated, it gives me some real world scenarios to consider. That's exactly the kind of information I was looking for. While we are busy with the research for our maiden overland trip, hopefully 2022 will be the year, my greatest anxiety is the fuel consideration. We are campers not overlanders so this is completely new territory for us. I would like to to do a short 4-5 day trip and then slowly increase our range to fully fledged 2-3 week trips. That's my dream...
    Use that short trip to gather real life consumption information and treat it like gold, it could save you a mountain of heartache. Here are my planning parameters for my 4.0l Fortuner, note this is what I use to plan it is higher than real life by about 10%. There's no towing number as we only have a roof top tent but we are generally heavily loaded for an overlanding trip.
    Open tar road 14l / 100km
    Gravel 16l / 100km
    Sand 18l/ 100km
    Heavy Sand 22km / 100km
    Heavy 4x4 driving 22km / 100 km

    Using the above in conjunction with the indicative speed from Tracks4africa I put together a spreadsheet including the distances to calculate the quantity of petrol required. For example the last two parameters are used when T4A indicate speeds below 25km/hour, gravel can be a bit deceptive but my parameter works for anything between 60 and 80km/hr. I often break my T4A section down to shorter segments in the rough country by putting in more waypoints as a check, this also gives you additional coordinates to navigate by if the track "disappears".

    An interesting anecdote we used a similar set of parameters for my son's diesel Triton for a trip to Gonarezhou adjusted downward by 10%. We seemed to be spot on except for the last two we he was actually closer to 25l/ 100km and overall I used only 5% more fuel than he did on the trip measured from Punda Maria - Gonarezhou- Punda Maria. So be very careful about assumptions, rather gather the data for your vehicle add 10% and in remote rough areas I usually add another 20L for getting lost or as we call it an unplanned scenic drive.

  13. #10
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    Regular fill-up also help a lot.

    Fill-up before doing a gravel section and then fill-up as soon as possible afterwards, this will give you real world figures for your vehicle at gravel road speeds.

    Do the same on the open road and when you do some low range and 4x4 driving.

    Regular fill-ups gives a much more accurate result for specific road conditions.

    Also, while you are doing regular fill-up, make notes of what the fuel gauge are showing and how much fuel you can put in. This will help you determine how much fuel is left in the tank. Lots of vehicles have more fuel in the first quarter or half tank of the tank than in the last half or quarter of the tank. (As indicated by the fuel gauge) Some vice versa

    Its a bit of a schlep but you will very quickly learn your vehicle's consumption in different conditions.

    Use notes or an app.

    PS. Know exactly what the capacity of your tank is! Test it yourself and don't go with the manufacture's specs.
    Last edited by DC Polokwane; 2021/05/04 at 09:21 AM. Reason: PS added
    Jeep Grand Cherokee 2002 4.7 V8
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  14. #11
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    Quote Originally Posted by Tony Weaver View Post
    The answer is the same as to the question, how long is a piece of string?
    Depends entirely on the terrain. If you are slogging through deep sand or mud in low range, all on-road, gravel, or high range averages go out the window.
    Absolutely. My normal on-road consumption in my Defender is approximately 9km/l. On our last overland trip, I got a consumption of between 7 and 8 km/l on a combination of tar and gravel roads. I was carrying a rooftop tent, plus extra spare wheel and 40l of fuel on my roof. When crossing the Namib desert, I got 4 km/l, driving mostly in low range.

    Terrain and weight both are factors to take into account.
    Last edited by Ellie2; 2021/05/04 at 11:26 AM.
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  15. #12
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    Default Re: Fuel consumption calculation for overlanding (planning stages)

    Quote Originally Posted by River Rat View Post
    Use that short trip to gather real life consumption information and treat it like gold, it could save you a mountain of heartache. Here are my planning parameters for my 4.0l Fortuner, note this is what I use to plan it is higher than real life by about 10%. There's no towing number as we only have a roof top tent but we are generally heavily loaded for an overlanding trip.
    Open tar road 14l / 100km
    Gravel 16l / 100km
    Sand 18l/ 100km
    Heavy Sand 22km / 100km
    Heavy 4x4 driving 22km / 100 km

    Using the above in conjunction with the indicative speed from Tracks4africa I put together a spreadsheet including the distances to calculate the quantity of petrol required. For example the last two parameters are used when T4A indicate speeds below 25km/hour, gravel can be a bit deceptive but my parameter works for anything between 60 and 80km/hr. I often break my T4A section down to shorter segments in the rough country by putting in more waypoints as a check, this also gives you additional coordinates to navigate by if the track "disappears".

    An interesting anecdote we used a similar set of parameters for my son's diesel Triton for a trip to Gonarezhou adjusted downward by 10%. We seemed to be spot on except for the last two we he was actually closer to 25l/ 100km and overall I used only 5% more fuel than he did on the trip measured from Punda Maria - Gonarezhou- Punda Maria. So be very careful about assumptions, rather gather the data for your vehicle add 10% and in remote rough areas I usually add another 20L for getting lost or as we call it an unplanned scenic drive.
    Thanks, and yes, the shorter trips are for exactly that purpose, test equipment and gather information. I am a habitual consumption checker for no other reason than its interesting. Whatever the calculation I'll be sure to add some fat to the figure, plan for the worst but hope for the best!
    Last edited by Craig Van der Poll; 2021/05/04 at 03:23 PM. Reason: grammar

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