Do you use less petrol in heavy traffic on the motorway or when its clear and doing 70 mph?

Question

Do you use less petrol in heavy traffic on the motorway or when its clear and doing 70 mph?

Answer 1

In town my Peugeot 406 2 litre returns UNDER 30 mpg. At an average of 70mph it will return 39 - 42 mpg - done it on many occasions.  It is impossible to get near the quoted figures, as these are done under controlled conditions - no other traffic etc. so manufacturers can con us  the paying public.

Answer 2

I drive a Honda Jazz  1.2 and get about 35 to 38 Mpg aaround town, but a couple of weeks ago on a 200 mile journey on motorways I got 60 MPG there and about 58 MPG for the return 200 miles.  Kept my speed under 70 MPH. i am usually quite heavy footed so I would think a lighter driver would be able to improve upon this. i think you have your answer

Answer 3

When you're moving at normal speed 45 to 55 is most economical but 70 is better than stop start as when you're stopped you're still burning fuel but not moving giving you 0mph so on average expect stop-start to  give you half the economy of  70mp or WORSE!

Answer 4

Normally, it is better mileage at cruising speed. That is why city miles (a lot of stopping and accelerating back to speed) are lower than highway miles.

EDIT: There is no such thing as a universal optimal cruising speed, as it varies by car, due to gearing, engines, etc... Your best bet is to stay as low in the RPM range of your highest gear as possible for peak MPG.

Answer 5

You will be doing more miles per gallon (mpg) travelling at 70mph on the motorway than you would do if you were stationary in traffic. The reason being, when you are stuck in traffic most people will still leave their engine running (in the vain hope that the jam might clear soon). An idling engine is still using up fuel even though your car isn't going anywhere so at that point you would be doing 0mpg. Even if the jam was moving slowly you would be doing less than 10mpg whereas moving at 70mph you would probably still be doing around 30mpg!

Answer 6

You use more petrol on the motorway because generally the traffic is stop and go, and you burn more to regain your momentum.

The ideal speed is constant speed.  You waste energy every time you step on the brake and then need more of it to get back to the desired speed.

Answer 7

You will nearly always use less fuel when you're cruising (at pretty much any speed). I think the optimal cruise speed tends to be about 50-60, but cruising at 70 is going to be a lot better than stop-starting in a traffic jam.

Answer 8

anything is better than conjestion. if you are cruising then your engine is used to doing a set number of revs so it uses less fuel, whereas with conjestion the revs are changing constantly so it uses more fuel than cruising.

hope this helps you.

Answer 9

It's more economical to be doing a constant speed;

Please note, despite EVERY time a question is asked regarding economy, someone quotes 56mph as 'the most economical speed' - this is rubbish, it's just that in the UK, cars used to be rated at 56mph & 75mph for economy - they're not a 'magic' figure at which your car's more economical.

Answer 10

56 mph is the optimal cruise speed