MPG getting better!!!!!!!

calleyw

I normally put 35L of petrol in my car and refill when I get down to the white line. Suppose to be a 40L tank with a 6L reserve!!!!

For the last couple of months I seem to be getting more miles to a tank of fuel. I use to get anything from 230-250ish to a tank. Today it was 297!!!! and the last few fills up have been 270+

I am rather perplexed by this.

1)my driving style has not changed
2) been told that fuel pump on it's way out. But it has been making that noise for probably a year or so.
3) not been serviced in probably 2/3 years I know!!!!I do abuse my car a bit but it still keeps going.

I filled up once at a different petrol station and then I started to get better MPG. But every other fill up since has been at my usual petrol station.

None of it makes any sense. Not spoken to a mechanic, but a few friends who know a bit about cars don't have any ideas either!!!!

Thanks in advance.

Yours

Calley

Ultrasonic

Your fuel economy has probably gone up because it has been warmer over the last couple of months.

To get a more accurate measure of your fuel economy you would be better using the brim-to-brim method rather than what you are doing now.

Strider590

As said, it's the warmer weather.

If you do mostly short journeys this effect will be even more pronounced.

Do I have to get technical? Ok just a bit.....

Your car basically runs on a fuel/air mixture, it's about 17:1 in favour of air, a modern car controls the fuel/air mixture to prevent under fuelling (which would damage the engine). I the old days we had a manual "choke".
So on a cold day, the engine takes longer to warm and is using more fuel during that warm up period. Once that temperature is reached the engine will run an normal efficiency.

<removed to prevent another pointless argument>

I don't know why your car friends didn't know this, unless you class "knowing a bit about cars" as having fitted a whaletale to a Ford Fiesta......

forgotmyname

That line is not an accurate way to measure the fuel level. Time it right and you could probably get somewhere close to 2 gallons in the car and still be on or near that line before and after.

colino

Yep. MINIs do that when the weather gets better. Less crosswinds, climate control isn't on and the elbow out the window makes them more aerodynamic.

calleyw

I know I am a girlie and an interesting theory. I am well aware of how an engine works using a mixture of air and fuel and that it uses more fuel when cold. One of the reasons why I 99% of the time reverse park in to parking spaces, also it allows me to get away quicker and also not deal with twonks who will walk behind a car reversing out of a parking space.

Also I have had my car for nearly 10 years. So think I do know it fairly well by now. And have never notice any massive jumps in MPG just during the summer months. Maybe a few extra miles to 35Ls on a long run when on holiday but that is one off. But we are talking up to nearly 70 miles difference on my usual runs. My car has been getting 230-250 for the last couple of years come winter or summer. How do I know that? as sad as it is I normally text myself when I fill up each time, what I get per 35Ls of fuel.

And yes I know the brim to brim is a much better method for checking mpg. But I am not going for exact mpg which is officially suppose to be 31 for my car. I also understand that a fuel gauge is not 100% accurate so running down to the white line is not the same every time and can also depend on other things. Which would explain the difference of approx 20 miles per 35ls of fuel.

One of the people I spoke to use to service aircraft engines as well as working on his own car and the rest are people who work on their own vehicles and have changed head gaskets etc. I have no idea what a whaletale is and am not going to look it up.

Thanks for the theory and it is something to mull over but not 100% convinced that is the complete answer.

Yours

Calley

anotherbaldrick

Have you, or someone without your knowledge pumped the tyres up perchance ? A whaletail is a bit like a tea tray but less useful.

I have found my MPG going up recently , I can only put it down to a change of brand , always stuck to the local Esso but last fill was BP and my consumption went up from 47 to 51 mpg (diesel Tiguan)

Strider590

calleyw wrote: »

Thanks for the theory and it is something to mull over but not 100% convinced that is the complete answer.

Yours

Calley

Was your car reaching full operating temperature during the cold months?

If your thermostat was stuck open it'd take forever to reach that temp on a cold day, this would mean using more fuel not only for the first few miles, but for the entire journey.......

More theory......
When the engine is cool, the thermostat prevents water flowing into the radiator, then it gradually opens up as the temperature increases. The purpose of this is to make warm up much more rapid.
If it was stuck, it would constantly push water into the radiator and as such the engine wouldn't get up to temp unless you were not moving and would in fact lose more heat the faster you were going.

It could well be that this is a recent phenomenon, not having been serviced there's a greater risk of the thermostat being gunked up.

worried_jim

I am getting 2mpg more compared to winter doing exactly the same journey- even have the a/c blasting as well.

Ultrasonic

calleyw wrote: »

Also I have had my car for nearly 10 years. So think I do know it fairly well by now. And have never notice any massive jumps in MPG just during the summer months. Maybe a few extra miles to 35Ls on a long run when on holiday but that is one off. But we are talking up to nearly 70 miles difference on my usual runs. My car has been getting 230-250 for the last couple of years come winter or summer.

I did note you were talking about quite a big change when I made my earlier post, but due to the innacurate way of measuring useage I was skeptical how big the change really was which was why I thought temperature was the most likely answer. It sounds like you're confident it's a real change in which case it is odd as you say.

FWIW my diesel car's fuel economy varies quite a bit with temperature (and the difference between summer and winter diesel), resulting in what I'd estimate to be between 10% and 15% mpg differences. I say estimate because although I record the mpg for every tank I don't have a driving pattern when any two tanks are comletely comparable. But that's comparing conditions with snow on the ground to our current attempt at summer...

How do I know that? as sad as it is I normally text myself when I fill up each time, what I get per 35Ls of fuel.

If you do that you may as well do it properly and record brim to brim mpg data . If doing it manually seems too much hassle then use something like fuelly.com, or one of the apps out there to track fuel economy.

Weird_Nev

Service the bloody thing.