[Closed] really sad and nerdy MPG driving thread.....

I did all that before driving up in summer (4000km round trip) and tbh the difference is that small you might as well go the easiest way. Little consolation saving 50eur in diesel when you've been stuck in Tours rush hour in 36° heat for an hour or two which means you miss your crossing and then end up on the M25 at 5pm etc etc.

Not suggesting you go via Tours btw, that'd be a bit of a detour...

They all go through Brussels. This is not a good thing.

To be honest, Autoroutes are like the Heathrow express. Sure there are cheaper alternatives, but they suck. There are some places you should spend money if you can, and this is one. Autoroutes are lovely.

Unless they are going around a city. Then they are as bad as any other city bypass.

Re MPG - avoiding cities will make the most difference. And driving consistently without hard braking.

hmmm.... train is booked for 7:50am. two hours leeway means i can get to Calais at just before 6am. should be able to avoid Brussels rush hour and leave the cruise control alone for much of the way.

went through the Ardennes via Trier (middle route on Google... not my address, btw) last time which was nice visually, but involved quite a few long hills.

is it geographically easier going via Luxembourg?

Re MPG - avoiding cities will make the most difference. And driving consistently without hard braking.

i know... hyper-miling.... i can bore the GF to death on this subject. she's not coming with me on this trip.

No real issue with Brussels. 90% of the time I go round the ring there a about 2:30pm on a week day, or thereabouts. Takes me typically 20 minutes.

I thought the standard accepted recommended route was... A8.. Luxembourg.. Namur.. Charleroi.. Lille.. Calais.

I never go that way since I'd need to go south and then across, and it's about 30mins further.

Dunno about mpg specifically, or total litres per getting from A to B. Slightly denser air overnight = moar power!

i may be living in Munich, but i don't drive like a Münchner... i don't have a firmenwagen or tankkarte. i have to pay for my fuel.

slow and steady... 😀

I like cruise control for motorways generally, I find it gives better economy. I only turn it off when it gets windy and hilly.

Acceleration kills MPG so the straightest and least hilly I would have thought would be the most fuel efficient. I think you use far more fuel driving up a hill than you save when coasting down.

I used to drive (the bulk of) this route all the time when I lived in Stuttgart. The answer to your question is "none of the above". The first option is almost the best but you need to hang a left at Namur before you reach Brussels and follow the E42 to Lille and up to Dunkirk. Aim to fill up in Luxembourg with fuel and fags to sell back home to fund the trip 🙂

I'd agree with Welsh Farmer, apart from the fact that the bypass around Lille is being ripped at the moment and the traffic queues are horrendous!

q wobliscott....that's what i want to know... which is the least hilly? as said, last time i drove via Trier, which was pleasant, but hilly.

driving thought the night should mean less traffic. although i've then got the M25/Dartford to contend with. will probably pay the crossing fee this time.

Wouldn't worry too much about the timing of the train. Quite often booked the cheapest around about the time we want and jumped on an earlier or later one. Always seems to have been space to get the van on.

Avoiding speeding would be a start.

Don't get you OP. You want good mpg, but then at the same time don't want to he caught by speed cameras!?

Simple solution ?

Leave the cruise control off.

[quote=Honest John]because it robs you of the sensitivity of control via your right foot. Motorways are surprisingly undulating. If you leave the tripmeter on "instant consumption" you can see the economy dive on an incline if you maintain speed. But if you lift off a little bit and lose maybe 5mph, you might maintain reasonable economy. On a descent the opposite happens. When you could increase speed without burning extra fuel, the cruise control slows the car and economy suffers.

Tempers seem to be fraying around the Calais Jungle, government is planning to disperse the 10,000 people around France so they are more desperate to get across, a number of attacks on drivers, trees dragged onto road, hay bales set alight with goal to create a traffic jam and jump on a lorry.

Leave the cruise control off.

I'd disagree with the cruise control thing. Unless the hill is so steep that up it the engine is engaging open circuit fuelling (generally around 90% throttle), or downhill that you're having to brake (neither of which are likely on a normal motorway) and assuming you're not in an automatic that's changing gear, the only advantage of losing speed whilst going uphill is that you're going slower therefore there's less drag (the same on a flat bit of road as well, if you drop to 65 from 70 for a couple of minutes, you'll use less fuel). Unlike the human body, engines don't use lots more fuel to get 90% performance vs less performance - in fact in a petrol car you'll use less due to reduced throttle losses - I've never seen anything evidenced other than heresay to suggest otherwise. edit : this also assumes you're not in a car that uses its brakes to keep a car at desired speed on cruise control - I guess those with adaptive cruise might do this, but normal cruise doesn't

you can disengage the engine going downhill - it'll use some fuel to keep the engine at tickover (assuming you don't turn it off - that's another question) - rather than no fuel if the road is driving the engine via the gearbox, but in theory the overall losses are less (because the engine is being turned over at idle - ~700rpm - instead of at motorway speed - ~2,000 rpm) - so the fuel used should be more than compensated by going quicker at the bottom - but things aren't that simple as the increased drag from going quicker is not a straight line relationship (I think it's cubed), and I don't know enough maths/physics to figure out the difference.

Either way, the differences between using/not using cruise and disengaging/not disengaging the engine are likely to be minimal. Find a lorry, sit as close behind it as you feel safe (3m behind might get you a 39% increase in fuel ecoonomy - http://www.autoblog.com/2007/10/28/mythbusters-drafting-10-feet-behind-a-big-rig-will-improve-mile/ ), and pick the shortest motorway route

if you want to geek out - this document

is about (american) trucks, but most of it probably applies to cars too. Whilst some of the numbers look pretty low, its worth noting that the base is around 5mpg, so 0.5mpg increase in the doc is the equivilent of 5 or 6 on a modern car. I found the worn tyre bit quite interesting 🙂

I reckon a careful, highly predictive driver can beat the cruise control without dropping speed.

The gains come from the lag in response that means a car under CC slows a fraction at the bottom of hills before the throttle reacts so the speed drops and needs to be replaced. All those little 2-4mph adjustments use more fuel than a lighter human push on the throttle at the transition from flat to uphill and seeing the crest and knowing when to ease back before it goes down again.

Then there's the ability to predict and feather to line your car up with a gap to change lanes that you can see maybe four cars back in your mirror. So you can drop from 70 to 68 slide into that gap at the right moment without braking.

With the cruise on the inclination may be to carry on at 70 longer and have to tap the brake to make the gap - suddenly you are doing 65 - need to gain 5mph not 2mph.

All marginal gains.

On the opposing side of the argument on an empty motorway when you might be tempted to leather it then CC has a huge value because it can cause you to stay at a more sensible speed with reduced drag (as per 5lab above) and save you from tickets. I nearly always use it when coming home from late night work functions/long hauls back from other bits of the country to make sure I stay economical and legal.

Unless the hill is so steep that up it the engine is engaging open circuit fuelling (generally around 90% throttle), or downhill that you're having to brake (neither of which are likely on a normal motorway)

Find a lorry, sit as close behind it as you feel safe

Whilst I'd agree with the 'hitting gaps' argument (on busier roads), I'd disagree with the former argument. A car under cruise will check speed ~100 times a second. When facing an incline there will be a marginal drop in speed, but probably less than 0.1mph. On the other side, a 'proactive' driver pushing the throttle early will increase speed ('needlessly') for a couple of seconds.

however, I don't think either of those are particularly relevant. As long as your not shifting gear, using so much power you get into open-circuit fuelling or using the brakes, a couple of mph for a few seconds here and there will make next to no difference on mpg (the only difference being the overall wind/tyre drag for the duration of that time).

They'll be doing 2/3rd the speed of cars (or a fraction of the speed on the steep uphills).
Oh and at that hour of the day, there won't be any trucks on the autobahn.

if you're going 50% quicker than a lorry on flat-ish sections I'd suggest you're not even trying to get good MPG. A quick google suggests there's no night-time ban on lorries in germany (only the sunday ban) - but that might be wrong. Obviously on very steep gradients different technique is needed, but I recon that'd probably be <5% of the overall drive