As a new owner, I've been keeping a careful eye on the fuel consumption over my Monday-Friday commute to/from work - a 20 mile trip (each way) with lots of stops/starts and a short piece of dual carriageway, keeping to the speed limit where possible.

A couple of things I have observed:

• Raising the tyre pressure to recommended values made a significant difference (all tyres were about 5/6 psi lower until I checked): 4mpg increase.
• Accelerating in gear up to 4/5k rpm before changing up rather than 2/3k (depending on road conditions): 2 mpg increase.

The first point I guess is no surprise (just underlines how important it is to regularly check your tyre pressures) but the second was not what I was expecting (goes against most fuel saving advice). Is a trait of this particular engine? It certainly makes the commute more enjoyable.

What year car? Mileage? What are your figures?

Are you doing proper brim to brim checks? I find the on board computer significantly optimistic most of the time, and sometimes wildly optimistic. Can find no pattern to error vs type of usage !

The biggest factor in variation of consumption is the effect of cold starts with short journeys, followed by winter/summer figures. I have figures from new to 10,000 miles - it has got signifiasntly better with time. I cannot post figures as I am away at the moment - but will post on return.

Thanks for your input but my question was more about the relative effects of driving style on this particular engine rather than absolute mpg. As I'm using the same measurement technique (onboard reading) over many, many near identical journeys, I'm hoping that the effects aren't dependent upon the factors you mention. For example, it could be that increasing mileage does help mpg but if I return to a more 'conservative' driving style, the increase I described in my first post disappears (so mileage has not affected it). Does that make sense?

Re driving style – I find leaving the `flight recorder’ on [inst mpg] flags-up the negative spots, e.g. hanging-on too long to a high gear.

I too record av.mpg every fuel-up, by brim2brim & read-outs - & find although there maybe some variation, this is negligible over time. I did think there was some av.mpg loss due to fitting new rear tyres, given they were >10% heavier than the worn pair – although I believe that loss was now more due to winter spec diesel.

I also keep my tyre pressure up at the top end of the pressure envelope. I recently found that the tyres are rated `E’ (Yellow label) for economy (RR) under the new label scheme - but haven’t yet discovered the rating for the newer rear tyres. I’m not sure if the argument is whether the variation is ± 1.5mpg between each A to G grade, or between each colour (Grn, Ylw, Red) code.

SpartanX said:

• Raising the tyre pressure to recommended values made a significant difference (all tyres were about 5/6 psi lower until I checked): 4mpg increase.
• Accelerating in gear up to 4/5k rpm before changing up rather than 2/3k (depending on road conditions): 2 mpg increase.

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You can generally raise the tyre pressure to 3-4 psi above what it says in the handbook. It'll be slightly less comfortable, but you'll get another 2-3mpg probably. Personal choice, since it's a tradeoff

Please don't rev your multijet above 4.5k rpm, it's not marked on the rev counter, but that is in fact the redline even though fuel cutoff doesn't happen until 5k rpm. I've never found the need to ever rev above 4k rpm in mine, since the power drops off sharply beyond that point.

On any single journey from A to B, the effect of the prevailing wind may be greater than the differences you are trying to measure.

I've made round trips on windy days where the trip mpg difference on the outbound and inward legs was in excess of 10mpg, with otherwise identical driving styles over the same roads.

If you're driving at a steady 60mph in a 10mph headwind, the aerodynamic drag on the car will be about double what it would be if you were driving at a steady 60mph in the opposite direction.

Caravadossi said:

Re driving style – I find leaving the `flight recorder’ on [inst mpg] flags-up the negative spots, e.g. hanging-on too long to a high gear.

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I'm not suggesting driving at a steady speed in a lower gear, rather accelerating through the rev. range. I have used the instantaneous reading but I dislike it because it distracts the eyes from where they should be.

I'm slightly sceptical about the fuel saving idea that suggests you change up early without qualification. Disregarding labouring the engine (which is obviously a bad thing), imagine the following situation: driving along at 30-ish in 4th gear (say), no traffic behind; ahead of you the speed limit increases to 60mph on an open, level road. Is it more efficient to change down and quickly accelerate through the gears to the new speed limit or to slowly accelerate in the gear that you are in?

I don't know the answer but my experience so far with this engine in this car would tend to suggest the former.

KozmoNaut said:

You can generally raise the tyre pressure to 3-4 psi above what it says in the handbook. It'll be slightly less comfortable, but you'll get another 2-3mpg probably. Personal choice, since it's a tradeoff

Please don't rev your multijet above 4.5k rpm, it's not marked on the rev counter, but that is in fact the redline even though fuel cutoff doesn't happen until 5k rpm. I've never found the need to ever rev above 4k rpm in mine, since the power drops off sharply beyond that point.

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Not suggesting doing either of these, although I find your comment about the 'redline' interesting: I've noticed no drop-off in power until nearly 5k but you're right, there's really no need to rev it this high.

jrkitching said:

On any single journey from A to B, the effect of the prevailing wind may be greater than the differences you are trying to measure.

I've made round trips on windy days where the trip mpg difference on the outbound and inward legs was in excess of 10mpg, with otherwise identical driving styles over the same roads.

If you're driving at a steady 60mph in a 10mph headwind, the aerodynamic drag on the car will be about double what it would be if you were driving at a steady 60mph in the opposite direction.

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Of course there will be some variation which is why I mention many, many journeys - these are 'average' observations if you like.

SpartanX said:

Not suggesting doing either of these, although I find your comment about the 'redline' interesting: I've noticed no drop-off in power until nearly 5k but you're right, there's really no need to rev it this high.

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Try accelerating at full tilt in 2nd or 3rd gear from 1500rpm until 5000rpm.

There is a very definite drop in power once you cross 4000rpm, it feels like the engine runs out of breath. You'll get much more progress in the next gear at that point. If there isn't, you're not driving a 1.3 Multijet.

Regarding the tyre pressure, why not? The only slight drawback is a small bit of comfort, but the fuel economy is increased and the car feels better through corners.

OK - I'll give this another go (probably don't need encouraging ). In your earlier post you said the "power drops off sharply" by which I take it you mean more noticeable than the influence of the power curve of the engine?

SpartanX said:

OK - I'll give this another go (probably don't need encouraging ). In your earlier post you said the "power drops off sharply" by which I take it you mean more noticeable than the influence of the power curve of the engine?

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Well, yes and no. The power curve dips quite severely at that point, but it's nothing like the fuel cut at 5000rpm. That one stops you good.

But there's absolutely no reason to ever get above 4000rpm, a higher gear will put you in a part of the power curve with much more on tap.

I've run my Panda MJ from March '05 when it was new to to date and have covered 62,000 miles, or 100,000 kms. Not the highest mileage you're ever likely to come across for 6 years of driving but there it is anyway.

Personally I find the trip computer to be a frustrating thing, although in my case it under-reads by between 5 and 10%.

My regular commute consists of 3/4 of a mile of 30 to 40 mph zones with 3 sets of traffic lights. This is followed by 13 miles of motorway and another mile of 30 limits. Incuding mucking around in town with occasional cross country routes consisting of higher limits this doesn't give much room for getting anywhere the rev limiter. My average consumption is around 56 - 58 mpg.

If you use the trip doofah, hills seem to offer the biggest resistance to good fuel consumption as even a slight gradient on the motorway will drop the instantaneous consumption from high 50s to high 40s.

The Beard said:

Personally I find the trip computer to be a frustrating thing, although in my case it under-reads by between 5 and 10%.

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Funny, the very same thing happens to me. Since I bought it, the average fuel consumption is 0,3 l/100km - 5 mpg - worse than real (brim-to-brim).

It's very hard to believe you get better fuel consumption revving at full to 5k rpm. Sorry mate! If there's something I learned with my Panda, is that fuel consumption rises sharply with hard accelerations. Rev it swiftly until 3k, then change up - it will sit again on the torque zone, and be comfortable again. Using full throttle means the engine will burn all the fuel it can, and if that's what to do to get maximum speed, the same cannot be said to get the best economy. That's why some cars have "ECO" buttons now - they limit the peak torque, so the engine isn't "allowed" to that maximum power stage.

The Panda's economy drops a lot with motion speed, and contrary to what most people think, the problem are not bad aerodynamics.
The Panda's cd, in standard shape (roof rails plus 155/80R13's) is 0,33. Not impressive, but the usual for a regular hatchback. Frontal area is not that big either, because it's narrow, despite being tall.
The problem here is engine speed. Thanks to a short-ratio gearbox, as soon you go past 52 mph - 84 km/h (there could be some variation from country to country, and 4x4's have even shorter ratios), you rev past 2k rpm. To go at 62 mph (100 km/h), the engine revs at 2400 rpm, at 77 mph (124 km/h) already 3k rpm. You may be putting little fuel into each cycle, but you're doing a lot of them!

Now I have a new job, my routine is this: thice a day, 35 km (22 miles) of hilly B-road at 70-100 km/h (43-62 mph), depending on gradient, plus 5km (3 miles) of city driving. Temperatures between 10ºC and 27ºC, 155/80R13's (Uniroyal Rainexpert - great, by the way) at 2.6 bar (yeeeeees, I prefer economy...). My monthly fuel consumption is 3.8-3.9 l/100km (72-74 mpg). Only managed this because I rev around the 2k rpm mark.

Oh, my original ContiEcoContacts lasted 60k km (38k miles), being over-inflated for most of the time and me cornering like a maniac (economy rules!!!). Cannot really understand complaints regarding this point!

Cheers from Portugal!

Our car, an Eco Active, has a very similar fuel consumption, but between 3K and 4K revs. It is noticeable that the fuel consumption drops in winter, and if it has been doing a lot of short journey the fuel consumption drops and stays low for while afterwards. On one occasion I had my foot down for about 3/4 mile when the engine was already hot, two things then happened:- the car had a flat spot at low engine speed, causing a bit a of a problem in traffic, and the fuel consumption jumped up by about 10 mpg. The effect lasted about 2 months. I have noticed this happen several times since then. It is noticeable that when driving on back roads, never using fifth gear, staying below 50 mph the mpg is quite high. Going back to motorway/dual carriageway driving at 60 -70 mph the mpg drops off noticeably, but at 70+mph with the engine running at over 3000 revs in fifth mpg goes up again. This is not what you would ordinarily expect to happen but is definitely what I have observed over more that a year.

KozmoNaut said:

You can generally raise the tyre pressure to 3-4 psi above what it says in the handbook. It'll be slightly less comfortable, but you'll get another 2-3mpg probably. Personal choice, since it's a tradeoff

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It is against the law in the UK, and you can face 3 penilty points and a £60 fine for EACH tyre that is out (either over or under inflated) by 10% iirc.

Most Easterly Pandas said:

It is against the law in the UK, and you can face 3 penilty points and a £60 fine for EACH tyre that is out (either over or under inflated) by 10% iirc.

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The Spark usefully has a separate 'eco' pressure listed on the door frame which is higher than the listed 'fully laden' pressure.
Although looking at my Fuelly banners below, it doesn't help that much.

Geddes said:

The Spark usefully has a separate 'eco' pressure listed on the door frame which is higher than the listed 'fully laden' pressure.

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That is interesting. Can you state the normal/fully-laden/eco pressures, please?

Most Easterly Pandas said:

It is against the law in the UK, and you can face 3 penilty points and a £60 fine for EACH tyre that is out (either over or under inflated) by 10% iirc.

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Wow, that's completely nonsensical.

What if you've put on bigger wheels and switched to tyres that have a significantly lower profile? Running at stock pressures on a setup like that could be dangerous.

Besides, who's going to check your tyre pressures?

Besides, who's going to check your tyre pressures?
Have a accident with the police involved and they check tyre depth and pressure as standard proceedure.Infact ive even seen traffic police check tyre pressures on spot checks .