Fuel efficiency question for mathematical/mechanical types

I drive a 1.2 litre Fiesta that does approx 48 miles per gallon.

I have the option of two routes to work. One is on the motorway which is a journey of 22 miles but there's hardly ever any traffic problems and I can easily stay at 70 the whole way there.

Option 2 is only 9 miles but involves travelling through Manchester city centre, never getting above 30mph and frequently having to stop for traffic lights, queues etc.

Which option would be most fuel efficient?

 

what direction is the wind blowing?

I reckon through the City.

 

I think I'd agree

Difficult to imagine without seeing how bad the traffic is.

Why not drive one way for a whole week and see how much fuel you've used, then drive the other way the second week and compare?

 

Go on the motorway - but at 50 mph.

 

9 miles?.............

much quicker by bicycle-and cheaper-and more fun

 

Not sure how old your car is but published figures for a new 1.2l Fiesta urban mpg is 34.4 while ex urban is 60.1mpg (assuming you believe the quoted figures!). Combined is 47.1mpg which fits in with what you're suggesting so near enough. Your 9 mile journey will use 0.26 gallons while your 22mile journey will use 0.37gallons therefore cheaper to drive through the centre of town. Of course I could be wrong, it has happened before.

Sorry just bored at work, doesn't say much for the job really does it!

 

OK here goes...

Fuel efficiency, in its basic sense, is the same as thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is often illustrated as a continuous energy profile. Non-transportation applications, such as industry, benefit from increased fuel efficiency, especially fossil fuel power plants or industries dealing with combustion, such as ammonia production during the Haber process.

In the context of transportation, "fuel efficiency" more commonly refers to the energy efficiency of a particular vehicle model, where its total output (range, or "mileage" [U.S.]) is given as a ratio of range units per a unit amount of input fuel (gasoline, diesel, etc.). This ratio is given in common measures such as "liters per 100 kilometers" (L/100 km) (common in Europe and Canada) or "miles per gallon" (mpg) (prevalent in USA and UK, using their respective gallon measurements) or "kilometers per liter"(kmpl) (prevalent in India). Though the typical output measure is vehicle range, for certain applications output can also be measured in terms of weight per range units (freight) or individual passenger-range (vehicle range / passenger capacity).

This ratio is based on a car's total properties, including its engine properties, its body drag, weight, and rolling resistance (friction), and as such may vary substantially from the profile of the engine alone. While the thermal efficiency of petroleum engines has improved in recent decades, this does not necessarily translate into fuel economy of cars, as people in developed countries tend to buy bigger and heavier cars (i.e. SUVs will get less range per unit fuel than an economy car).

Hybrid vehicle designs use smaller combustion engines as electric generators to produce greater range per unit fuel than directly powering the wheels with an engine would, and (proportionally) less fuel emissions (CO2 grams) than a conventional (combustion engine) vehicle of similar size and capacity.

 

yep I was just going to say the same thing!

 

RE: OK here goes...

cut n paste? out with blah chavs tonight?

 

RE: OK here goes...

nah mate, stopping in, my pink shirt is in the wash, you out in Chennels with the old fogeys...????

 

RE: OK here goes...

lol I don't go in that particular pub very often.

and I bet you're older than me.