Fuel Consumption and Range Disparity

[pmaisey Lurker Find all posts View Profile Close pmaisey]

My 2012 150 Prado shows I'm consuming 9.8l/100k's average and after I fill the tank (150 litres) to the top, it only shows around 1200km of range. I've checked that on 3 fills now.

On my calculation, 9.8 lp100k = 10.20 km/litre. If I've got 150litres on board I should have a range of around 1530km. (10.2 x 150)

I used to fill up and the range would always be around 1500, but we did a trip to Vic/NSW from Perth and back in late 2022 and it was after that I noticed the difference.

I have reset all the counters for average consumption, trip A and trip B but that has had no affect.

Any ideas?

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

Probably worth remembering:

• Your tank capacity is 150L but in reality if you spent the time and removed all air pockets and filled the tanks to the top of the filler there is probably room for almost 160L (but no one would ever spend that much time at the pump due to the diesel foaming and other venting issues getting the air out of the tanks.
• Your fuel gauge sensors will register at full 83L out of the 87L in the main tank and 59L of the 63L in the sub-tank so max fuel range calculations can only use 142L as the max available fuel.
• The low fuel light is triggered with between 25L and 30L remaining.
• The fuel system warning on the center display comes on with approx 10L remaining but this level due to the in-tank pump being fuel cooled creates the risk of damage or premature failure of the pump due to overheating or blockage due to crap concentrated at the bottom of the pump.

So conservatively your initial fuel range should be based on around 120L x the default (which seems to be approx 10 km/l) or your average fuel consumption recorded by the engine computer.

[Leethal Advanced Member Find all posts View Profile Close Leethal]

Have you actually calculated your consumption or are you just relying on the onboard fuel computer? The early fuel computers were not 100% accurate so most times will be incorrect hence it is best to note your milage and litres to fill and calculate it from that.
Calculated range will also be based on 130 odd litres rather than completely dry, that is needle on E.

[pmaisey Lurker Find all posts View Profile Close pmaisey]

Have you actually calculated your consumption or are you just relying on the onboard fuel computer? The early fuel computers were not 100% accurate so most times will be incorrect hence it is best to note your milage and litres to fill and calculate it from that.
Calculated range will also be based on 130 odd litres rather than completely dry, that is needle on E.

I have just been working off the computer, but was curious as to why it would change from the 1500 to the 1200. I will do a physical test of actual litres to kms on the speedo and see what that gives me. Thanks for the reply.

[pmaisey Lurker Find all posts View Profile Close pmaisey]

Probably worth remembering:

• Your tank capacity is 150L but in reality if you spent the time and removed all air pockets and filled the tanks to the top of the filler there is probably room for almost 160L (but no one would ever spend that much time at the pump due to the diesel foaming and other venting issues getting the air out of the tanks.
• Your fuel gauge sensors will register at full 83L out of the 87L in the main tank and 59L of the 63L in the sub-tank so max fuel range calculations can only use 142L as the max available fuel.
• The low fuel light is triggered with between 25L and 30L remaining.
• The fuel system warning on the center display comes on with approx 10L remaining but this level due to the in-tank pump being fuel cooled creates the risk of damage or premature failure or the pump due to overheating or blockage due to crap concentrated at the bottom on the pump.

So conservatively your initial fuel range should be based on around 120L x the default (which seems to be approx 10 km/l) or your average fuel consumption recorded by the engine computer.

That's good info re the reserve levels and something to keep in mind so thanks for that. Still not sure as to why it would drop from 1500 to 1200 on the gauge. I'll do a physical check - actual litres in vs kms travelled on odo and see what that comes up with. At least then I should have an ideal of my actual range after a fill up. Thanks for the reply.

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

10l/100km is pretty good for the old 3l. I find the fuel reading notoriously optimistic, usually out by at least 10%. Disappointing as the other 3 cars in the family, Subaru, Nissan, and Skoda, the computer is dead on.

[404pug Avid PP Poster! Find all posts View Profile Close 404pug]

Interestingly my 2016 computer is very accurate like within 1 or 2 percent

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

You asked about the 1500 to 1200 km - Did you disconnect / have a flat the battery or blow an ECU fuse or do any sort of memory reset around that time?
As these will reset your long term average L/100km to the default in the computer.

[pmaisey Lurker Find all posts View Profile Close pmaisey]

No battery or fuse, but I did reset the average consumption reading and two trip meters. It was showing the lower level before and after doing these resets.

[watsea Member Find all posts View Profile Close watsea]

For my vehicle, I do not regularly look at my range from day to day, but I am concerned when the range shown is extremely optimistic, especially when I am towing or going in hard conditions. Obviously there is a residual memory of past fuel usage when lower fuel usage that is hard to overcome.
When towing or going in hard conditions, I use some mental arithmetic with the fuel gauge contents and the fuel usage "since last start" to estimate my range. My experience with tank fills at the servos has given me confidence with my tanks' contents. I have found the range becomes less optimistic when fuel tank contents gets very low. Once, after not been able to get fuel at a few servos because of a large region power outage, I had been towing a caravan into a headwind, I was glad that I reached a working servo with some fuel still in my tanks. The range showed as 24 kilometres. I had intended not going past that servo until it could supply fuel. Luckily it could. I think that I added 131 Litres but could have added more, if I filled slowly. There was queue waiting.