Lexus Fuel Consumption Figures

[fastegg]

When cruising in my '98 LS400, the fuel consumption readout shows 8.2Litres per 100km's. This would mean that with an 85 litre tank, i should be able to do 1000km's per tank full and thats impossible. When cuising on the hwy, i get about 650km per tank which is about 12.5 km per 100km. I live in Gosford and a drive to my mums up the hwy to Port Macquarie is 400km... thats an 800km round trip so if i fill up in Gosford, i should easily get back home (800km) with plenty left in the tank which it wont, i have to fill up before half way home. Now i don't know if my maths are correct but 8.2L per 100km = 1000km with an 85L tank yes ? Could someone varify this ?

[Lexus Nerd]

When cruising in my '98 LS400, the fuel consumption readout shows 8.2Litres per 100km's. This would mean that with an 85 litre tank, i should be able to do 1000km's per tank full and thats impossible. When cuising on the hwy, i get about 650km per tank which is about 12.5 km per 100km. I live in Gosford and a drive to my mums up the hwy to Port Macquarie is 400km... thats an 800km round trip so if i fill up in Gosford, i should easily get back home (800km) with plenty left in the tank which it wont, i have to fill up before half way home. Now i don't know if my maths are correct but 8.2L per 100km = 1000km with an 85L tank yes ? Could someone varify this ?

Hi fastegg,

a) I take it your tank was full when you left Gosford. When you refill your car, do you stop at the first click, or fill it till it is nearly overflowing?

b ) When you refilled the day you travelled back from Port Macquarie to Gosford, how many litres did you have to pay for? Eighty-five litres? 80?

c) The fuel consumption readout: Is it the type that you initialise at the beginning of the trip, and it slowly changes the farther you travel? Or is it an instantaneous reading, so that it shoots up when you stop the car, or drops down dramatically when you're going downhill and your foot's off the accelerator?

Edited August 5, 2011 by Lexus Nerd

[fastegg]

G'day Lexus Nerd...

I understand your questions but with respect they don't mean anything... My issue is that my fuel consumption readout says i'm averaging 8.2L per 100km which means is should get 1000km per tank when hwy cruising but at best i'll get 650km per tank which is 12.5L per 100km. In fact, who ever heard of a UCF21 LS400 getting 1000km per tank ?

So, are Lexus fuel consumption figures total B.S. ?

[Lexus Nerd]

G'day Lexus Nerd...

I understand your questions but with respect they don't mean anything... My issue is that my fuel consumption readout says i'm averaging 8.2L per 100km which means is should get 1000km per tank when hwy cruising but at best i'll get 650km per tank which is 12.5L per 100km. In fact, who ever heard of a UCF21 LS400 getting 1000km per tank ?

So, are Lexus fuel consumption figures total B.S. ?

Hey fastegg,

There's two questions here: Is the reading of 8.2L/100 km correct, and did you calculate 12.5L/100 km correctly?

The '98 LS400 is rated at 7.6 L/100 km on the highway. The reported consumption of 8.2L/100 km is higher, but expected, given that your engine revs at 100 km/h would be higher than in the 80 km/h lab test. The LS has a combined cycle consumption rating of 9.2 L/100 km, and you would expect your trip in northern NSW (predominantly highway, despite the traffic) to be lower than that. So the 8.2L reading "sounds" reasonable.

Now, about the calculation of 12.5L/100 km ... If you, say, refilled when the car is 1/4 full (which some people insist on, to prevent being caught out on the highway with no fuel, or to supposedly prevent engine damage), and stop at the first click (which some people do to prevent overflowing), then my guess is that you would have only used around 58 litres over the 650 km, which is 8.9 L/100 km. Alternatively, a problem with the fuel gauge could mean that the gauge reads low when your tank isn't low on fuel. That's why I asked

( b ) - if you started with a full tank, and refilled the tank till it's full, then the amount of fuel you paid for on refill will indicate exactly how many litres of fuel you used over the 650 km.

Edited August 9, 2011 by Lexus Nerd
I keep on getting a smiley when I enclose "b" in parentheses

[fastegg]

I understand what your saying, however, if my dash display is saying i'm averaging 8.2L per 100km that means i should get 1000km per tank full. This is my whole point... 1000km per tank ????

[Lexus Nerd]

It's plausible:

- The official consumption figures of a 2011 IS are just a little lower than the 1998 LS, and some drivers on this forum can get 1100+ km on a 65 L tank.

- Your LS is said to be more economical than most six-cylinder petrol-driven family sedans, and has a tank 10-15L larger.

But we won't know for sure unless someone's actually tried it.

[fastegg]

If i fill the car up, reset my dash display... drive up the pacific hwy to port macquarie.. when i go to fill it up again, the fuel readout says i'm averaging 8.2L per 100km... so i fill it up and the fuel readout says i now have 650km in the tank if i keep driving the way i have been driving, which is false, it should say i have 1000km in the tank which is 8.2L per 100km.

Showing me 650km remaining, is indicating 12.5L per 100km... What the ?????

[Lexus Nerd]

If i fill the car up, reset my dash display... drive up the pacific hwy to port macquarie.. when i go to fill it up again, the fuel readout says i'm averaging 8.2L per 100km... so i fill it up and the fuel readout says i now have 650km in the tank if i keep driving the way i have been driving, which is false, it should say i have 1000km in the tank which is 8.2L per 100km.

Showing me 650km remaining, is indicating 12.5L per 100km... What the ?????

Ahhh, the "distance to empty" readout ... I've never known one of those to be accurate in any car. Reset your trip meter, drive exactly 10 km and you'll probably find the distance to empty hasn't changed from 650 km. Shouldn't it change to 640 km? Well, I bet it won't.

I believe the readout is meant to be a very, very conservative guide ... which is a nice thing if you're about to head from, say, Adelaide to Perth. You wouldn't want it to overstate your range when there's no petrol stations for hundreds of k's!

[fastegg]

I guess when i get my LS back from the painters, i'll do some serious mpg road tests and get to the bottom of it.

I'll bet i'll get nothing like 8.2L per 100km... it'll be more like 12L per 100km.... thats my gut feeling anyway...

.

.

Ahhh, the "distance to empty" readout ... I've never known one of those to be accurate in any car. Reset your trip meter, drive exactly 10 km and you'll probably find the distance to empty hasn't changed from 650 km. Shouldn't it change to 640 km? Well, I bet it won't.

I believe the readout is meant to be a very, very conservative guide ... which is a nice thing if you're about to head from, say, Adelaide to Perth. You wouldn't want it to overstate your range when there's no petrol stations for hundreds of k's!

[Greavett]

I agree on the basis that what it says is using you should be getting your 1000kms. But you have to realise that as good as Japanese electronics are, they would not be as accurate as you are hoping. From memory, they calculate from speed, and throttle opening, intake air. Now if you have larger/smaller wheels and or tyres fitted or problems with your Throttle position sensor etc this would give you strange readings also. I'm also pretty certain that when they do the lab tests that they have as little electronic load as possible, no aeronauticle drag etc. Some stretches of road here are always getting a head/tail wind, and that has a huge effect. A/C can take a bit off your fuel mileage also. And cruise control is never the most economical either.

The 1UZ-FE engine was and still is one of the most fuel efficient V8's you can get, but you can't expect miracles lugging a heavy car around. I'm pretty sure you can purchase more cutting edge fuel metering technology which may give you a better idea of where your car is at!

I remember seeing a driving tips advert in the back of an old Renualt hand book, saying windows, wheels tyres, etc. All simple stuff to remember costs fuel mileage. But it's often over looked when fuel economy comes into question.

No help, just a thought process!

Simon

[phantom007]

The fuel consumption depends on fuel octane, how much air pressure in the tyres, wind direction and speed, your speed and acceleration etc.

I have travelled over 1000kms on a tank a few times but only on solely highway driving.

The old way to check is to fill up and note the mileage or set the trip meter, drive your trip and fill up again, note how much fuel you put in and the mileage again, this will give you how much fuel you actually used in the distance.

With your reading of 8.2, maybe your tank can take more fuel to properly fill up.