What uses more fuel? A 5 mile 20 minute journey, or a 15 mile 20 minute journey?

Legacy_user

Im confused at which would use more fuel


Journey A is a 5 mile journey mainly at 20-30mph.

Journey B is a 15 mile journey at 60mph on motorway.

Both journeys take 20 minutes.

Elliott_Fox

I think A would use more, 30mph roads have a lot more stop starting and engine strain.

HappyMJ

15 mile journey will use more.

You could get an accurate answer by using the mpg figures for your car. Use the urban mpg for the stop start journey and the other one for the motorway.

example
20mpg then 5 miles will use quarter gallon
30mpg then 15 miles will use half gallon.

motorguy

I guess ultimately, is a car only 1/3 as economical on short runs, as it is on long runs?

I would say its probably 1/2 as economical, therefore route B would use more fuel BUT route B would be better for the engine.

1886

Hard to answer without knowing both routes but what I would say is that if the shorter commute consists of lots of stop start driving and changing gear then that journey will almost certainly use more fuel.

Coming to a standstill and then starting off again is awful for mpg as the engine has to work hard to get the car moving again and back up to speed

artbaron

If your car is in excess of 3X less economical on urban driving than motorway then journey 1 will be more expensive, otherwise journey 2. Off the top of my head I can't think of a car this applies to so I'd say journey 2 is almost certainly more costly.

GolfBravo

motorguy wrote: »

I guess ultimately, is a car only 1/3 as economical on short runs, as it is on long runs?

I would say its probably 1/2 as economical, therefore route B would use more fuel BUT route B would be better for the engine.

I guess it really depends on a car.

A couple of years ago there was an article in German Auto Bild comparing fuel consumption over a distance travelled. The worst offernder was Kia Ceed diesel - starting with cold engine within the first 3km (around 2 miles) it did something like 6mpg, and the warmer the engine got the better the fuel consumption. The manufacturer claimed mpg was reached after travelling around 12km (8 miles).

According to their test the best results were achieved by cars with the highest bhp/kg.

fivetide

berbastrike wrote: »

Im confused at which would use more fuel


Journey A is a 5 mile journey mainly at 20-30mph.

Journey B is a 15 mile journey at 60mph on motorway.

Both journeys take 20 minutes.

Pretty sure this isn't even possible.

In journey B 60mph is one mile a minute so that's 15 minutes not 20 minutes.

In A a distance of 5 miles in 20 minutes is 15mph average. That could either be crawling along or stop/start which would have a big effect.

Also, what car? what engine? what fuel? Just too many variables to give an accurate answer i'm afraid.

System

fivetide wrote: »

Pretty sure this isn't even possible.

In journey B 60mph is one mile a minute so that's 15 minutes not 20 minutes.

In A a distance of 5 miles in 20 minutes is 15mph average. That could either be crawling along or stop/start which would have a big effect.

Also, what car? what engine? what fuel? Just too many variables to give an accurate answer i'm afraid.

I wasn't conducting a scientific experiment just a guide, stop being so fussy!

bsms1147

You're asking 20mph vs 60mph



The second option, the longer journey at a faster speed, will use less fuel. The difference is made even bigger if the first route is stop/start.

Granted that's a generic graph, and yours will depend on the exact car and other factors, but it's as good an answer as any.

artbaron

bsms1147 wrote: »

You're asking 20mph vs 60mph



The second option, the longer journey at a faster speed, will use less fuel.

Not according to your graph.
20mph = 25mpg
60mph = 30mpg

5 miles @ 25mpg = 1/5g
15 miles @ 30 mpg = 1/2g

So journey 2 will take 2.5X more fuel, not less.

(edited: 15 miles not 20)