'Petrol efficiency experiment; an increase of 20%' blog discussion

MSE_Martin

mushypeaman wrote: »

Been trying all this for a week now, and been subjected to a fair amount of aggro from other drivers, including a couple of shouted threats, due to not accellerating away from traffic lights quickly enough; slowing down too early (for them) when approaching junctions/roundabouts. Unpleasant.

How strange - in all the time I've been doing it - I've never had this happen once. Maybe you're going a touch too slow.

Alternatively do you have a big car. I drive a smart so I thin people assume (not that correctly) its not too fast - and maybe that mitigates it.

almillar

Mushypeaman - you're doing it wrong. Drive progressively, drive to go, not to stop. If the lights are green, keep going (unless you KNOW they'll change), if the roundabout is clear, it's more economical to slow down less, as it means you'll have to accelerate less on the other side. Don't hold up queues of traffic! Try only doing all the economy stuff when there is no-one behind.

Dave72_2

....the problem is though that you need to save the most fuel when in heavy traffic - when there are lots of people around! Its at these times the engine is at its lease economical state (much worse still if you have just started off on a freezing morning - I even see the difference in my little diesel Polo).

Once upto speed, provided you keep moving the engine is much more economical (better still once the engine is warmed up).

Anyone got a car with engine Stop-Start feature. Does this improve the mpg a lot or a little, and how is it to drive in stop-start traffic situations?

kevanf1

Apologies if this has already been mentioned. I keep seeing the words "when filling the tank" or similar. Actually, a big way of saving fuel is to not fill the tank. By only half filling your tank you are saving that other half in weight (not delving into the petrol increases/decreases with temperature argument). By saving that weight your car does not have to work quite so hard to lug around an extra half a tank of fuel.

It has also been mentioned that the computer in a car is not very accurate. I can accept that but, it does give an indication of when you are driving more economically (if you have the sort that gives you average consumption etc) so I use mine as a guide. It's amazing how high the consumption goes up when I deliberately put my foot down quickly. Let's just say my foot very quickly becomes a lot lighter again

almillar

KevanF1 - the amount you save carrying the extra weight will be far outweighed by a special, or long trip to the petrol station. Never mind the time spent doing the above. Fair enough if you live next door to the cheapest petrol station in your area, but I just don't find it worthwhile.

Panther_Black

We've been driving 'slowly' to work whenever we can for almost 32 years now and have saved an average of £20 per Month, which equates to a lovely holiday each year - and we arrive at work much calmer. I really enjoy travelling to work now - I go early and calmly driving along, I actually see the countryside waking in the morning - Owls fly by the side of my car sometimes - beautiful.

Passing this info onto staff at work, they were sceptical but some tried and are amazed at the savings.
The planet is running out of resources so petrol will continue to rise in price and our roads are getting ever more 'glogged' so take your time and catch up those who keep wearing out their brake pads and paying loads more for petrol and there is very little more satisfying than catching up those that fly by you 20 miles previously - wicked!!

My favorite website - I discovered it!!!! First!!!! :money:

The_Miser

I disagree with a number of writers; as Martin writes, a full tank of fuel takes more power to haul it around so, if possible, keep your tank under half full. Windows shut, winter heating is recycle and not fresh air. Ensure there are no extraneous bits hanging from the bottom - like polythene etc. Martin has already said "keep your boot empty" (but carry a triangle, first aid and bulbs - they weigh ounces.)
Watch a long way ahead - if the lights are red or there is a traffic build-up then coast immediately because starting from a dead stop or very slow uses a lot of go-juice.
Don't get annoyed by other drivers - it pushes your right foot down hard! For any speed there is a wide-ish range of accellerator settings; you want your foot so high off the floor that the car j u s t keeps the speed you decide ( you could put your foot down harder and keep the same speed with more fuel wasted).
Avoid short journeys because it takes a lot of fuel to heat the engine and oil; use the bus or, better, shank's pony for better health (if you can)

All cars are different so this is my experience. My diesel Focus estate (65,000+ miles)does about mid 40's mpg ordinary driving (herself!) but I struggle to acheive 70mpg and get well over 67mpg (all on the in-car computer) on long distances. Ideal revs are about 1500 rpm - going down to 1000rpm for town driving takes more fuel. This allows me to follow speed-regulated lorries - 56mph though I prefer 50mph. Yes, it takes longer to get to York from London but a 66% saving on fuel for a pensioner with time to spare? - make up your own mind.

As for the man who actually did over 100mpg on a trip from John o'Groats to Lands End (or vice versa) - please tell me how it is done.

charlieheard

The_Miser wrote: »

I disagree with a number of writers; as Martin writes, a full tank of fuel takes more power to haul it around so, if possible, keep your tank under half full. Windows shut, winter heating is recycle and not fresh air. Ensure there are no extraneous bits hanging from the bottom - like polythene etc. Martin has already said "keep your boot empty" (but carry a triangle, first aid and bulbs - they weigh ounces.)

I couldn't disagree more. Half a tank of fuel weighs around 20kg, compared with a car and driver weighing around 1.25 tons for a small family hatchback. As almillar mentions above, you'll waste more than you save by having to divert to the petrol station twice as often. And there's no point recycling the air in your car - it just causes the windows to fog up. Cars generate too much heat: that's why they have radiators to get rid of it. Heating the air that goes into your car just means that less heat is rejected through the radiator. You won't save on drag because cabin air is taken from a high pressure area where the air's moving slowly anyway.

The_Miser wrote: »

All cars are different so this is my experience. My diesel Focus estate (65,000+ miles)does about mid 40's mpg ordinary driving (herself!) but I struggle to achieve 70mpg and get well over 67mpg (all on the in-car computer) on long distances. Ideal revs are about 1500 rpm - going down to 1000rpm for town driving takes more fuel. This allows me to follow speed-regulated lorries - 56mph though I prefer 50mph. Yes, it takes longer to get to York from London but a 66% saving on fuel for a pensioner with time to spare? - make up your own mind.

As you say, all cars are different, but most modern diesels just don't function efficiently below about 1500rpm - you can feel them struggling below this. However, petrol engines operate most efficiently when they're at lowish revs and large throttle openings - less pumping losses in the engine. So making sure the engine isn't struggling around town will do more for the fuel consumption than grinding it along at low revs. Once out of town, by all means get into the highest comfortable gear.

If by "following lorries", you mean slipstreaming them, that is incredibly dangerous. To get the effect, you need to be so close that you wouldn't even have time to react and move your foot to the brake pedal if they stopped suddenly. I wouldn't want to chance hitting the back of a lorry at 50mph however much fuel it might save!

I do agree that keeping your speed down and driving less aggressively saves fuel. I now travel at 70mph max on motorways, trying to keep far enough away from the car in front that I don't need to touch the brake pedal, and it's bumped up my consumption significantly over cruising at higher speeds. Doing this, I managed to get 80mpg out of my Micra diesel on long journeys instead of 55-60mpg. London to York (200 miles) that meant 2.5 gallons instead of 3.6 - a saving of 1/3! I'm sure that 50mph would improve it more, but it would add over an hour to the journey...

FATBALLZ

charlieheard wrote: »

And there's no point recycling the air in your car - it just causes the windows to fog up.

Not to mention it's dangerous to recirculate the same air for long periods of time.

Dave72_2

mark88man wrote: »

Hey Young-Uns, have you heard of a choke?? Well I bet you haven't heard of negative choke. I found this pretty cool - brought back a few memories.

we still had manual choke when I first started driving. In the early days it worked better than the automatic chokes.