Tuning Fuel Consumption

[Anniebee]

I just don't get this.

On Thursday night I drove from Falmouth to Cardiff and started off with a full tank of petrol. then on Friday morning I drove 10 miles to my destination and the fuel light came on to tell me I was down to 77 miles left ( according to the range display).

So, I filled it up again and then drove back to Falmouth that afternoon - and only used half a tank??

I swear I didn't drive up there in 3rd gear or anything stupid, so I'm flummoxed

Anyone got any ideas?

 

[DraigFlag87]

Shape of road/hills etc, load carried, wind direction, weather, type of fuel, traffic etc can all affect this, more details required please!

 

[Anniebee]

Same load carried there and back.

Same type of petrol, although , not from the same garage, obviously.

Weather there and back was dry, can't say as I noticed any particularly strong winds.

Surely Cardiff can't be that much uphill?

 

[DraigFlag87]

Same load carried there and back.

Same type of petrol, although , not from the same garage, obviously.

Weather there and back was dry, can't say as I noticed any particularly strong winds.

Surely Cardiff can't be that much uphill?

I reckon when you filled up again, you brimmed it? Waited until the pump stopped from the feedback? In this case, you would have filled it right to the nozzle almost, and i must admit, it takes a very long time for it to show on the display. I can do almost 100 miles, even in the Abarth, before a notch disappears when i fill right up. So it all depends, Thursday night, did you fill right up? Or had you been driving before hand?

 

[Zakt]

Same load carried there and back.

Same type of petrol, although , not from the same garage, obviously.

Weather there and back was dry, can't say as I noticed any particularly strong winds.

Surely Cardiff can't be that much uphill?

It's on the coast, so you're right - it's not uphill.

Was there a difference in your speed?

 

[Anniebee]

Well, to be fair, I usually don't try and fill it much past the automatic stop at the garage, maybe a couple of wee clicks that's all.

I drove from home where I filled up, to work, and then from work to Cardiff, but where I work is only 5 minutes drive from the A30, so no biggie. Then, the return journey was straight to home.

 

[DraigFlag87]

Well, to be fair, I usually don't try and fill it much past the automatic stop at the garage, maybe a couple of wee clicks that's all.

I drove from home where I filled up, to work, and then from work to Cardiff, but where I work is only 5 minutes drive from the A30, so no biggie. Then, the return journey was straight to home.

I would put it down to:
1. The inconsistency/inaccuracy of the digital fuel gauge
2. The fact that you used a different garage could have meant that fuel stopped going into the car earlier than the other one might have done on the auto-stop thingy.
3.Could have had a wind blowing towards you on the way there and a tail wind behind you on the way back, now THAT makes a huge difference which you may not have noticed at the time. Can make a few hours difference on a flight for example.

 

[Caravadossi]

So, I filled it up again and then drove back to Falmouth that afternoon - and only used half a tank??

If you’re only getting around 30 av.mpg then your estimates aren’t far out. Assuming a 9.9 gal tank? Although I’d argue into-wind drag would be a significant factor. (I believe Concorde could do NY to London in less than 3 hours with a tail wind).

Consider …

Outbound
220 miles @ 30mpg = 7.33gal (reserve = 2.57gal [or 77mls])

Inbound
Then 7.52gal(2.57+4.95) @ 30mpg = 226 miles (reserve = 4.95 gal)

As well as a variation at each brim-up – what error will there be in your “half-a-tank” estimate? Also the range remaining reading can rapidly change in seconds.

You need to look at all your flight-recorder readings & not just focus on a couple. What was your av.speed & travel time readings?

.

 

[durukan]

fuel gauge is not that sensitive. light come up when there's still a quarter tank of fuel. besides, sometimes i look at the display and say wow i did 320 km with a half tank, 50 more then usual, then after 5 km gauge goes down. then i realize, the last time i paid attention to it was when gauge had just pointed half a tank. what i mean is, fuel gauge shows the same approximately about 50 to 100 km, so it can be deceiving. the difference is probably 1/8 of a tank in your case i think, and this may well be explained by your driving style and weather difference. just reset trip a or trip b data everytime you brim to be sure that there's nothing wrong.

 

[306maxi]

I just don't get this.

On Thursday night I drove from Falmouth to Cardiff and started off with a full tank of petrol. then on Friday morning I drove 10 miles to my destination and the fuel light came on to tell me I was down to 77 miles left ( according to the range display).

So, I filled it up again and then drove back to Falmouth that afternoon - and only used half a tank??

I swear I didn't drive up there in 3rd gear or anything stupid, so I'm flummoxed

Anyone got any ideas?

This thread is useless without brimming and litre figures!

What the gauge says and shows is kind of useless without actual litre figures. I'll show you why.

When I fill my car up I brim it so I can't get another drop in. Consequently I've actually put more fuel in than the gauge will show. I actually get 100 miles out of it before it shows 7/8ths of a tank.

So depending on the fuel pump you fill up at you might not even be getting a full tank (according to the gauge) and therefore it will go down to half full earlier OR you could be putting in a little bit more fuel than the gauge can recognise and it will look like you're doing better on fuel.

Personally I think my scenario is probably what's happening as the 500 can take at least an extra 7 or so litres more than Fiat say it can.

 

[RobW]

i really don't get this obsession with fuel consumption

i fill the car with fuel and drive it until the range is less than where i want to go

then repeat

 

[YouKnowWho]

i really don't get this obsession with fuel consumption

i fill the car with fuel and drive it until the range is less than where i want to go

then repeat

You don't do enough miles then.

I had years, where I have driven 35,000 miles in one year. 10mpg over 35,000 is not a trivial amount.

 

[RobW]

You don't do enough miles then.

I had years, where I have driven 35,000 miles in one year. 10mpg over 35,000 is not a trivial amount.

incorrect - i do approx 40k a year including 10 trackdays at approx 10 mpg :devil:

if i was bothered about fuel economy i would have a diesel

if fuel is costing you too much do less miles or change your car for a more frugal one

no point moaning about it or the cost of fuel being £1.20 a litre http://news.bbc.co.uk/2/hi/business/8569525.stm

 

[306maxi]

i really don't get this obsession with fuel consumption

i fill the car with fuel and drive it until the range is less than where i want to go

then repeat

Ditto But by careful driving and putting more fuel in than others I generally go further than other people

 

[udtrev]

Ditto But by careful driving and putting more fuel in than others I generally go further than other people

Yep, you do quite well

 

[Cucciolotto]

i really don't get this obsession with fuel consumption

i fill the car with fuel and drive it until the range is less than where i want to go

then repeat

If I could thank you 1000 times I would! :worship:
Good Lord, the only thing I care about fuel is to have enough in the tank to drive from and to home, end of. And as far as I'm concerned the price of the fuel never changes, I always put £20!

 

[RobW]

and as far as i'm concerned the price of the fuel never changes, i always put £20!

brilliant!

 

[YouKnowWho]

incorrect - i do approx 40k a year including 10 trackdays at approx 10 mpg :devil:

if i was bothered about fuel economy i would have a diesel

if fuel is costing you too much do less miles or change your car for a more frugal one

no point moaning about it or the cost of fuel being £1.20 a litre http://news.bbc.co.uk/2/hi/business/8569525.stm

Fair play, but you get to know your car after so many miles - and if suddenly you are doing lower miles than normal ... you ask why! This would be the case for anyone who watches how much juice they get out of every tankful regardless of whether its a diesel or not.

TBH the price of petrol going up isn't a big thing for me .. but think of it this way .. if they put up the price to £10 per litre, or £20 per litre ... would it bother you then? I am assuming yes ... so there is a point before travelling to work to and from by car is no longer cost effective.

You can only go so far, by changing cars - this is not an option for everyone anyway.

No people's whose livelihood is affected by the fuel increase and/or loss of economy should be thinking about it.

 

[YouKnowWho]

If I could thank you 1000 times I would! :worship:
Good Lord, the only thing I care about fuel is to have enough in the tank to drive from and to home, end of. And as far as I'm concerned the price of the fuel never changes, I always put £20!

My mum always ask me, whenever I propose a car for her ... how many miles does it for £10 of fuel ... she doesn't grasp if the cost of the fuel goes up, the miles come down.

 

[306maxi]

I like to keep a tab on things. It's hardly a hardship for me to type in the amount of litres of fuel and the odometer reading into my phone. Put it into fuelly and it works everything out for me. There's no harm in keeping track of things now is there?