Noticeable drop in MPG after service...

Booner! · 30 Sep 2008 at 13:47

Not a biggy... but my MPG has dropped since my last small service.

For example, my mpg reader would say: 67mpg cruising at about 30 in 4th gear, now it says: 45mpg or lower..

Thicker oil or tyre pressures come to mind... but I am no expert... any ideas? Doesn't bother me too much because I just about get 35mpg on daily commute still (poor I know...)

paradigm · 30 Sep 2008 at 13:51

Instantaneous MPG readings are about as useful as trying to run using your tongue rather than your feet.

Any number of factors could be attributing to such a difference in instantaneous reading, most likely your right hoof.

Peter Diffey · 30 Sep 2008 at 14:09

Maybe they replaced your airfilter with a sock?

lordrobs · 30 Sep 2008 at 14:20

paradigm said:
Instantaneous MPG readings are about as useful as trying to run using your tongue rather than your feet.

Any number of factors could be attributing to such a difference in instantaneous reading, most likely your right hoof.

Exactly.

Brim it, reset the trip, brim it again then get your calculator out if you are that worried about fuel consumption.

I have to do this due to my obsessive nature. In fact entering the data into my spreadsheet and updating my graphs gives me a warm fuzzy feeling inside

Booner! · 30 Sep 2008 at 15:17

This is based on day to day usage over the passed few months and I have it up on the dash all the time to remind me not to boot it. Usually it goes to 67mpg ish with my foot at cruising position....now it seems to rest at about 45-53mpg at the same foot positon.

I know it's very inaccurate, but when you drive to work on the same roads doing the same thing every day there is patterns.... my pattern has changed and only since my service.

So based on the above, what could cause this? or have I turned into an OCD freak.

Firestar_3x · 30 Sep 2008 at 15:22

1.6 Golf and 67mpg? Not in a million years i'm affraid

Current readings sound correct.

Booner! · 30 Sep 2008 at 15:25

Yes yes I know.... I get an AVERAGE of 35mpg on the 15mile journey, which is frankly terrible etc.

What I mean is, the onboard active MPG reader shows roughly 67mpg upon cruising....whether it's doing this I don't know....but now it's doing 45-53ish on the active mpg reader....which affects the average slightly.... this has only happened since my service...that is all. I just wanted to know why it would do this?

Do I need to take a photo of what I mean?? *wipes sweat from forehead*

Firestar_3x · 30 Sep 2008 at 15:26

Nope your talking about the instant readout, i can make mine read whatever i want tbh!

Trip computer reset by the service people could have knocked some sense into it.

paradigm · 30 Sep 2008 at 15:28

Firestar_3x said:
Nope your talking about the instant readout, i can make mine read whatever i want tbh!

Precisely.

I can get my LCR to say 300+ MPG (before it jumps to infinity "---").

As I said in the first reply, instantaneous MPG is about as useful as an egg and spoon race to decide the next PM.

So long as your overall average hasn't changed, then quite frankly, no-one (including yourself) should give a flying fig.

Firestar_3x · 30 Sep 2008 at 15:29

paradigm said:
instantaneous MPG is about as useful as an egg and spoon race to decide the next PM.

We would have ended up with a better PM, i think you need to do an on-line poll to make this the new methord of getting into number 10!

Booner! · 30 Sep 2008 at 15:29

I find it useful to prevent me using my heavy foot from making my asthmatic engine cry any further.

izzy eckerslike · 30 Sep 2008 at 15:29

67 mpg in 4th gear ? Are you talking about instant consumption where if you lift your foot off it shows 99mpg

paradigm · 30 Sep 2008 at 15:30

Booner! said:
I find it useful to prevent me using my heavy foot from making my asthmatic engine cry any further.

Alternatively, just gain some self-control. Or indeed, just forget about it completely.

izzy eckerslike said:
67 mpg in 4th gear ? Are you talking about instant consumption where if you lift your foot off it shows 99mpg

Glad to see you've read the entire thread.

izzy eckerslike · 30 Sep 2008 at 15:31

LOL, thread dies a slow death, I'm a slow typer

bledd · 30 Sep 2008 at 15:36

booner..

out of interest, what do you get on a motorway trip?

need to replace my old vectra with something that has sensible MPG soon.

to work & back, i average around (15 miles to work) 36mpg (lots of stop/starting and a bit of motoroway)
on motorway & bit of a roads trip (110 miles) 55.2 -70mph top speed
on motorway & bit of a roads trip (110 miles) 42.4 -80-85mph top speed

greengiant · 30 Sep 2008 at 19:05

bledd. said:
booner..

out of interest, what do you get on a motorway trip?

need to replace my old vectra with something that has sensible MPG soon.

to work & back, i average around (15 miles to work) 36mpg (lots of stop/starting and a bit of motoroway)
on motorway & bit of a roads trip (110 miles) 55.2 -70mph top speed
on motorway & bit of a roads trip (110 miles) 42.4 -80-85mph top speed

I don't think thats a bad MPG. Petrol engine?

mrk · 30 Sep 2008 at 19:19

This is why I use the real-time MPG dial to control throttle/economy

no matter what the OBC says you can pretty much guarantee good economy if you keep the real-time needle on the good numbers if you want to get good economy on a specific journey.

It might not be 100% accurate but it's a good way to measure throttle position in relation to fuel burning compared to using a digital readout which jumps from 30 to 80 in the blink of an eye.

The digital readout value can change by several MPG quickly just by driving excitedly on just a single road then sensibly the next road.

Usually when I get 500 miles from 58 litres I leave the OBC on a constant read from my last fillup and at the end it reads around 37MPG or as it is now, 36.1 but the true calculated figure is actually 39.19MPG.

The analogue needle is the best one to use, not the digital one

Tom|Nbk · 30 Sep 2008 at 19:39

Mine changes daily for fun. It's now settled at 31MPG AVG

I agree with your MRK, even though the Analouge may not be accurate as such it's pretty handy thing to have.

Booner! · 30 Sep 2008 at 19:48

bledd. said:
booner..

out of interest, what do you get on a motorway trip?

need to replace my old vectra with something that has sensible MPG soon.

to work & back, i average around (15 miles to work) 36mpg (lots of stop/starting and a bit of motoroway)
on motorway & bit of a roads trip (110 miles) 55.2 -70mph top speed
on motorway & bit of a roads trip (110 miles) 42.4 -80-85mph top speed

I get something like 39-41mpg MAX on a motorway trip doing about 80mph fluctuating. Avoid the golf if you want MPG satisfaction, you have pretty good figures already (in comparison).

mrk said:
This is why I use the real-time MPG dial to control throttle/economy

The analogue needle is the best one to use, not the digital one

I don't have an analogue, it's not a feature on the dash.

mrk · 30 Sep 2008 at 19:52

The strange thing is though MPG does not go down for me going from 70 to 80 MPH, for example the average OBC MPG increased slowly as I cruised at 80MPG recently. That's just a bit less than 3500rpm but a constant cruise at 80. It did not drop, just either very slowly went up or stayed the same.

It's the slower speeds around town that drop it for me.