Mpg

[chatman]

12p/mile!! I thought the gov figure was 40p/mile. That what we get at work, and they are not known to give anything away!!

It is if you use your own car and do not get any car allowance.

I get a car allowance (they stopped company cars :( :( ) so its 12p mile at the moment until the Government bigwigs decide change it or loose another couple of cd's.....

[dave.m]

:o :o :o using that calculation its £4.909 per gallon. James Hunts the lot of them.

[Fujisan]

What's gallon's Granddad?

Isn't that the ship Johnny Depp sailed on?

[chatman]

What's gallon's Granddad?

Isn't that the ship Johnny Depp sailed on?

No Fuji that was the BLACK PEARL..................

This is what they should install at all garages now after seeing the prices....

[Uncle Bob]

What's gallon's Granddad?

Isn't that the ship Johnny Depp sailed on?

Cheeky f**ker :P

Now the EU has told us we can keep our miles and pounds, then why can't we still use gallons ....i'll tell you why, the petrol companies like litres because it looks less money

[NMaria]

I too keep an eye on fuel economy with different fuels but found that, although initially I thought BP Ultimate produced more mpg, the results were inconsistent. Changed my engine oil to Millers and that did make a difference. Much quieter and a bit more fuel-efficient.

The dash computer overstates fuel economy by around 7mpg - up from 3mpg when I first bought it. Isn't that bizarre? So when it says 52mpg and I work it out when I fill up, it's actually 45mpg. Does anybody know if it can be calibrated or adjusted? If it keeps going up, it will soon tell me I am doing 200mpg.

[anchorman]

Hi Maria

Not seen you for a long time!

Try re-setting the display by holding it pressed for a few seconds. It will read high at first then settle down. Mine does the same as yours and although I don't get much better fuel consumption from high grade diesel it is much quieter as the cetane rating is higher (it is less volatile and more controlled in burning).

I don't belive you can play with the callibration. The best way is by calculation as the digi display is only a guide to show you for example whether changing gear improves consumption.

Regards

[chatman]

phew drove down to Bath Wednesday night...in quite frankly the worst weather I've known...strong side winds and heavy rain...made interesting driving on the M25 and M4 behind and passing those lorries....

Still RAV behaved it's self and shrugged of the trip brilliantly..and to top it off Trip diplayed 49mpg (I know I know a bit aprehensive but after taking in deviation worked out about 45mpg) also the fuel is a bit cheaper here £1.06 compared to £1.08 at home....

[Nightstalker]

I knew I should have gone for a Diesel....apparently my rav is supposed to give me 30mpg...RIGHT!! more like 24mpg...and at these fuel rates...kin greedy government

[anchorman]

kin greedy government

here here

[shcm]

The dash computer overstates fuel economy by around 7mpg - up from 3mpg when I first bought it. Isn't that bizarre? So when it says 52mpg and I work it out when I fill up, it's actually 45mpg. Does anybody know if it can be calibrated or adjusted? If it keeps going up, it will soon tell me I am doing 200mpg.

It's an interesting point (well it is to geeks like me). I keep a record of fill ups and amongst other things calculate the "error" between dash mpg and calculated mpg. On my 4.3, the "error" also appears to have a trend which is slowly getting bigger. Graph shown below. Wiggly red line is the error, yellow line is just a smoothed version of the red line.

The dash mpg is reset at each fill.

Now, there is a whole load of errors that can creep in and I'm not suggesting this is that accurate, but there does appear to be something there. Never had such a big "error" (max 5.5 on 4.3 RAV) on the 4.2 RAV.

The thing is almost certainly going to be using integrated speed signal and injector pulse widths to do the calculation (well it's how I'd do it I think).

Anybody got any wacky theories or suggestions (apart from telling me to get a life :D ) to explain this trend?

[anchorman]

Well.......

When I had a company car I paid private mileage calculated on average fuel consumption for the period. If you did the sum on the average of the average the mpg got higher and the cost got lower. The accountants stopped us from doing it in the end but if there is anybody cleverer at maths than me (should be quite a few ) they might explain it. Does your trip computer stabilise/zero the climbing trend if you re-set it?

[Fujisan]

I knew I should have gone for a Diesel....apparently my rav is supposed to give me 30mpg...RIGHT!! more like 24mpg...and at these fuel rates...kin greedy government

Sorry...your only solution is a block of wood UNDER the loud pedal! ;)

[matfrost]

Does the fuel consumption computer not register fuel consumption when stationary?

If so the inaccuracy could be due to the fuel used while stopped in traffic.

Might be wrong though, its just a guess..

[shcm]

Well.......

When I had a company car I paid private mileage calculated on average fuel consumption for the period. If you did the sum on the average of the average the mpg got higher and the cost got lower. The accountants stopped us from doing it in the end but if there is anybody cleverer at maths than me (should be quite a few ) they might explain it. Does your trip computer stabilise/zero the climbing trend if you re-set it?

Averages of averages eh? Very dodgy :D. No, I reset the trip every fill up (if that's what you mean), so I hope I'm comparing like with like (approximately).

Does the fuel consumption computer not register fuel consumption when stationary?

If so the inaccuracy could be due to the fuel used while stopped in traffic.

Might be wrong though, its just a guess..

I think if you stationary with the engine running, eventually you can begin to see the average mpg begin to drop. I will have to check though. :)

I'll have another think about it and have a look at the figures. I can speculate on all sorts of things like tyre wear, injector wear, slight common rail pressure change.................. but all that seems a bit far fetched at the moment. Doesn't really bother me, I'm just curious as to the cause really.

Cheers

[bitman]

I knew I should have gone for a Diesel....apparently my rav is supposed to give me 30mpg...RIGHT!! more like 24mpg...and at these fuel rates...kin greedy government

you can also improve your fuel consumption by normal acceleration (let spinning away from the traffic lights to the boy racers) and use the engine to break your speed instead using the brakes to much.

i see here in the uk to many people only see using there brakes and also going down hill with the clutch depressed and on the brakes instead using the engine to brake the speed (just put it in a lower gear but keep an eye on your rpm of course).

if you use engine brake the ecu closes the fuel to the engine, but if you use only the brakes (clutch depressed) the engine still ticks over and uses fuel. this is a simple lesson we got when we did our drivings lessons that was for me some where in the beginning of the eighties.. we are now in 2007...

[anchorman]

I reset the trip every fill up (if that's what you mean), so I hope I'm comparing like with like (approximately).

No shcm I mean reset the average fuel consumption not the trip mileage. At the moment it is showing the average from new. If you press and hold the RH reset button it will zero your AFC and start again. It will then show garbage for the first 10 or 20 miles until it settles down but then it will stabilise after establishing some representative info.

[shcm]

No shcm I mean reset the average fuel consumption not the trip mileage. At the moment it is showing the average from new. If you press and hold the RH reset button it will zero your AFC and start again. It will then show garbage for the first 10 or 20 miles until it settles down but then it will stabilise after establishing some representative info.

Sorry Anchorman, we are talking about the same thing - it's my mode of "speech". I don't always write what I mean or make it clear. The whole lot does get reset by me at fill up - av mpg, mileage trip. So the calcs should compare like with like approx I think.

The first few miles at an alleged 50 or 60mpg after fill up (it's usually a downhill run for me for a while after fill up) are great Soon comes back to something more sane though.

Cheers

[anchorman]

Okey Dokey

Steve (of Aberdeen) seems to do the best - even when he checks it by calculation (and trust me you don't need to check his reckoning). I thought I was quite steady but he consistently gets good figures.

So, maybe we need to go to Aberdeen for some driving style lessons!

Steve, if you pick up on this, what do you do - get it in 6th for most of your low speed driving or come down the box a bit?

Regards

[Steve@Aberdeen]

Okey Dokey

Steve (of Aberdeen) seems to do the best - even when he checks it by calculation (and trust me you don't need to check his reckoning). I thought I was quite steady but he consistently gets good figures.

So, maybe we need to go to Aberdeen for some driving style lessons!

Steve, if you pick up on this, what do you do - get it in 6th for most of your low speed driving or come down the box a bit?

Regards

With winter coming on which means headlights on for most journeys, demister and a/c on for longer to keep windows clear, my average is dropping a bit. I also had a couple of runs in a hurry so I've dropped to around 44 at the moment.

When I learnt to drive, my father had a Standard Vanguard III which had a 2l long-stroke engine - petrol but bags of torque for the day and you usually pulled away in 2nd and up to 4th once moving; 3rd was only needed in heavy traffic and 1st for starting on a hill or with a caravan. That got me into the habit of using low revs that, nowadays, makes me happier with diesels.

I had a motorbike for a couple years (a Honda 175 for the commute to work); it took a few weeks to get into the habit of revving it hard - until I did, fuel consumption was terrible. Peak torque should be the engine's most efficient point so running in this band will give best fuel consumption - and, with their flatter torque curve, and lower rev band, diesels can return better all-round performance. My father also, when teaching me, encouraged me to imagine a glass of water on the bonnet - drive without spilling any.

The main ways to save fuel are (in my view):

1) Don't accelerate harshly unless necessary (welly it if you need to when pulling into a gap on a busy road, of course, but don't try to race away from lights, etc).

2) Remember that the speed limit is meant to be the fastest you go on the road, not the minimum or an average, so target 65-70 on a dual carriageway or 55-60 on a normal A road.

3) Use the gearbox to keep the engine in its most efficient rev range; on the D-4D I reckon that should be around 2000. I tend to run 1700-2500; it pulls easily from there but don't let the engine labour too hard.

My $0.02 worth.

[Fujisan]

Some very wise words, thank you very much Steve.

[anchorman]

Thanks.

I don't think I'm doing a lot different in terms of revs and accelerating but I tend to do 70-80 (indicated) on dual carriageways and motorways.

There is also a very steep hill on the way to work which I cannot help gunning up it. Probably does 10mpg for that minute or so which will drop the average. Maybe I'll try going around the flatter way for a bit!

Cheers

[bitman]

when i pull away i try to keep my rpm's at around 2000 rpm (if possible) since it's a auto it accelerates by it self. also when approaching a traffic light i use the O/D off switch to brake on the engine. ;-)

just try to find the max. torque in your manual / specs book of your engine and use that with your rpm's. this will give you the best fuel / power balance.

but the most important thing is your EYES. see what happens in front (and not only the first car in front of you but even before that one) of you so you can adjust your speed. know your road etc etc. driving is about 80% watching with your eyes.

[anchorman]

Absolutely bt.

The other good point you made is that these modern engines completely shut off the fuel on over-run providing a very efficient engine brake.

[chatman]

Managed to get to Bath Wednesday night...then to client's site Thursday morning (up very steep hill) then drive back Thursday night taking detour off M4 to miss M25 chaos at Heathrow...

Then also managed to get to work Friday morning....believe trip comp was on 360 miles.....not bad I say...averaged at 45mpg after fill up on Friday.....