Problems with petrol comsumption

victor2

I always got "better" mpg from a tank full of petrol from one particular station - and lower mpg from the previous tank full if I had filled it up somewhere else. Always filled the tank until the pump cut off and then added a bit. Figured it was due to the forecourt slope going away from my filler cap, allowing me to get more in.

Fuel guages are pretty vague as well, so an indicated quarter tank could mean anything. My needle would stick at full for about 50 miles after I filled the tank.

Gloomendoom

reduceditem wrote: »

One swallow doesn't make a summer.

The OP has not had 93 miles from a tank, they THINK they've had 23 miles from a quarter tank which is a bit different.

Could be a lot of reasons, the most likely being that they did not completely fill their tank at the last petrol stop. That could be due to the petrol foaming up, or the garage forecourt being on a slope etc, which would give the impression of a full tank.

Eggzackerly. Which is why I asked the OP how they had measured the fuel consumption.

I think all the reasons you outlined above are a lot more likely than a change in the weather.

vikingaero

Sometimes I think I've filled up the car and find that the pump has clicked early and rather than having a full tank I've only got 2/3rd of a tank.

The other issue is that in my experience Japanese and Korean cars have fuel gauges which seem to stay on full for ages and then drops rapidly in between half and empty.

fred7777

I always let the tank run to almost empty then fill it back to full and note the fuel consumption. I started doing this with my first car (an unreliable X reg Metro) and among other things it lets me know if anything is wrong with the car.
So based on that I'd say take it in to a Garage ASAP, however there are a few things to check first:
1. Tyre pressures, Changes in weather and encounters with pot holes can make big differences which will effect fuel consumption. Check the pressures and look at the tyre tread - it should be even depth all the way across if not then there is a possible problem.
2. Check the warning lights, they should all light up when you turn the key to start the engine to let you know they are all working. I once had a car which got low on oil at the same time as the low oil light failed!
3. My current car's fuel gauge does jump around from time to time when the weather changes by about an 1/8-1/4 of a tank, it's possible yours is doing the same and it will go back up in a few days time.

reduceditem

fred7777 wrote: »

I always let the tank run to almost empty then fill it back to full and note the fuel consumption. I started doing this with my first car (an unreliable X reg Metro) and among other things it lets me know if anything is wrong with the car.

That only works if you fuel up at exactly the same place each time, because of slopes in forecourts, different fuel brands etc.

Even then you still have to account for weather and foaming.

Mobeer

reduceditem wrote: »

That only works if you fuel up at exactly the same place each time, because of slopes in forecourts, different fuel brands etc.

Even then you still have to account for weather and foaming.

Best thing to do is for a long period (say a month), record the litres of fuel bought, month starting mileage and month ending mileage, both starting and ending the month with a full tank. This gives a long term average figure that takes into account different types of driving, different drivers, different traffic etc.

fred7777

That only works if you fuel up at exactly the same place each time, because of slopes in forecourts, different fuel brands etc.

Even then you still have to account for weather and foaming.

Yes and no, there are differences but it's pretty consistent between 700-750 miles per tank. If I suddenly got 500 miles or the fuel gauge was indicating that was what I could expect then I would be having a look for a fault or taking it into a garage.