Cheapest Petrol & Diesel Discussion Area

JDPower

I-LOV-MONEY wrote: »

How did you do it? Did you fill up immediately after the trip (from full) to see how much petrol you used?

The only problem is that you are wasting petrol experimenting !

No I just trusted the cars average MPG dash readout. Yes I may have wasted petrol a bit experimenting in the short term but now I know there is a significant consumption difference in knocking off 10mph (plus some other techniques I tried in my little mpg game) I can knowingly save petrol/money in the long term

JonnieShah

grizzly1911 wrote: »

I am sure the fuel comes from the same supplies but as JPP says it depends on who pays for it and accounts for it.

Tesco 'branded' fuel is supplied by Texaco, in which Tesco owns a share. Esso 'Tesco' petrol stations sell Esso fuel, the Tesco is just an add-on convenience type thing.

Mark_Hewitt

I-LOV-MONEY wrote: »

If I have a 10 mile journey and leave my house earlier and drive slowly (to 30mph limit !), is there going to be much of a fuel saving form going at say 40mph ?

There will be some, yes. In general all things being equal 30mph is going to be more fuel efficient than 40mph. However there are so many factors, gearing, traffic, hills etc etc.

The only way to know for certain is to do a scientific test of both and see the results.

However driving at 40mph in a 30mph is not to be recommended in any case.

I-LOV-MONEY

Mark_Hewitt wrote: »

There will be some, yes. In general all things being equal 30mph is going to be more fuel efficient than 40mph. However there are so many factors, gearing, traffic, hills etc etc.

The only way to know for certain is to do a scientific test of both and see the results.

However driving at 40mph in a 30mph is not to be recommended in any case.

Thank you Mark.

It would be too expensive to carry out a scientific test, besides the traffic conditions are likely to differ each time.

I just wanted to know on average if the costs are going to be much different.

I didn't mention anything about driving at 40 on a 30mph road!!

John_Pierpoint

Most cars are designed to get the best figure in the compulsory tests and the engine is probably pretty efficient at 2,000 RPM.

However the energy is wasted by
1. Using the brakes (or the gears) to slow down

The energy in a moving body is proportional to its mass and the the SQUARE of its speed. As you drive along in your vehicle it has to accelerate away a block of still air.

2. The speed of the vehicle.

So the significant saving by slowing down is greatest at the 80 MPH end of the range, rather than at 40 MPH

http://www.theaa.com/public_affairs/news/20mph-roads-emissions.html

http://www.green-car-guide.com/the-secrets-behind-official-mpg-v-real-life-mpg.html

I-LOV-MONEY

Very interesting. I often use a stretch of road approaching traffic lights, which gives me clear visibility all the way to them. I have been known when there are no other vehicles in front, to let it go into neutral (yes I am aware of the risks). So while I am coasting am I burning fuel, obviously the engine is still running.

I drive an automatic.

Mark_Hewitt

You'd get better milage if you didn't put it into neutral. As in neutral the engine will still be burning fuel to keep it from stalling, if you leave it in gear the wheels will be turning the engine so it will be using NO fuel.

I-LOV-MONEY

Surely leaving it in gear means it is using more power to keep the wheels moving. Presumably when in neutral the wheels are turning because they are round and are going downhill.

colino

You really cant generalise about cars like this. Sure, drive with a feather foot, anticipate well, brake less and keep useless extra weight out of the car (she can walk). You will have to drive in as high as appropriate for the conditions, without the engine labouring and not needing to constantly drop down gears to keep up with traffic or floor the throttle because you havent been concentrating. Experiment a bit and it will fill up a boring commute; but saying things like keep to a certain speed or engine rev just wont work. For example, even feather-footing my (auto) car for a week to let it "learn" the settings it still would never go above third gear - out of six- at 30mph.

I-LOV-MONEY

colino wrote: »

keep useless extra weight out of the car (she can walk).

LOL Now, why didn't I think of that ?!

Better still .. use her car!