Fuel saving - it's not what you drive....

AdrianHi

Fuel saving, it's not what you drive, it's how you drive it.
A rather extreme example was on Top Gear the other night.
For those who did not watch it they took a new Toyota Prius and drove it around their test track as fast as they possibly could (I know, it's not what the Prius is about but stay with me). Following the Prius just fast enough to keep up was a new V8 BMW M3 which has over 400bhp compared to the Prius's one hundred and something.
The Prius managed 17.2mpg and the M3 19.2mpg :rotfl:

Discussing this on another motoring forum with some other people we started exchanging stories of other cars with bigger engines which we found, in the real world, how we used them got the same or better fuel consumption than smaller engine cars.

Here are my examples based on mostly A road and motorway driving, not much town driving:

1998 Mitsubishi Galant 2.5L V6 official combined 29.5mpg, I averaged 33mpg, got 36mpg on a run.

Skoda Felicia 1.3 4 cylinder official combined 38mpg? driven the same journey still return 33mpg

1982 Citroen Dyane 6 (2CV variant) official combined 45mpg, on the same journey again returned.... about 33mpg and went a good 10mph+ slower that the above cars.

1997 Nissan Primera 2.0L petrol, official combined 32.5mpg, on similar journeys... 33mpg again!!!!

2005 BMW 320d (diesel) touring official combined 47mpg, I get 46mpg and up to 53mpg on a run - at February 2008 fuel prices it was costing me the same to fuel as the V6 Galant just over 2 years earlier.

So as Jeremy Clarkson was saying on Top Gear, don't go selling your 2.0L petrol Mondeo for 2p (because everyone else is doing the same), it's not "money saving", adjust the use of the car and driving style as best you can. You could end up changing for a car with a better official combined mpg which is little better off in your driving conditions and it will cost you to change.

Anyone else observed same or better mpg from bigger engined cars on open road / motorway driving?

tomstickland

Well it's going to be a combination of the car,driving style and type of use it's put to.

A small and light car requires less work to move it around, so will generally give better mpg. Run an engine at the design load and a small engine will give better results than a large engine. Run the test at higher speeds and the small engine will be way off its design point and poor mpg will result.

Driving a steady 60mph on a flat A road and a 1.1 or 1.3 106 will give much better mpg than a 3.0 V6. Do the same test at 90mph on a hilly motorway and the larger engine could start to win out.

Small engines only really provide good mpg if driven near their design point, which normally means quite slowly or not being worked at all hard. For UK A and B roads I reckon that 4 cylinder 1.8 and 2.0 petrol engines are pretty much optimum for medium sized cars.

banger9365

i takes a program like topgear to wake poeple up about changing there way off drive and not the car they drive ,well done TG
it's about time

skim

All said & done if you use a 1980's car as a daily driver you are being more environmentally friendly than driving a new car. Most of the pollution/waste is in the manufacture so for a few pence per mile difference you are better off using an older car.
1980's cars can offer just as much economy as a car today.

BillScarab

I'd agree with the above except I think diesel engines around 2 litres will give better fuel economy than petrol engines. As an example I drive an Octavia 1.9 tdi which averages 47mpg although to and from work it can go up to 52-54mpg. My wife drvies a Suzuki Swift 1.3 and she only gets 31mpg but her miles are all around town and relatively short journeys.

EDIT: Just to say it may work out cheaper to buy and run a petrol car than a diesel but in pure fuel economy terms a diesel will be better.

hewhoisnotintheknow

the example on top gear proved nothing really, as for those prius things they are awful for the planet!

anewman

AdrianHi wrote: »

Skoda Felicia 1.3 4 cylinder official combined 38mpg? driven the same journey still return 33mpg

Should do better than that wonder if it had had the valve clearances adjusted and a good set of spark plugs. I can get 45mpg on a long motorway run with an older version of the car in estate form if I'm careful and driving at 60mph. 75mph gets me about 39mpg.

AdrianHi

anewman wrote: »

Should do better than that wonder if it had had the valve clearances adjusted and a good set of spark plugs. I can get 45mpg on a long motorway run with an older version of the car in estate form if I'm careful and driving at 60mph. 75mph gets me about 39mpg.

I think it would be down to driving at indicated 80 to 85mph where the fuel economy is probably dropping off fast and the fact that 1/3 of that journey was country lanes with lots of stopping for junctions.

AdrianHi

BillScarab wrote: »

I'd agree with the above except I think diesel engines around 2 litres will give better fuel economy than petrol engines. As an example I drive an Octavia 1.9 tdi which averages 47mpg although to and from work it can go up to 52-54mpg. My wife drvies a Suzuki Swift 1.3 and she only gets 31mpg but her miles are all around town and relatively short journeys.

EDIT: Just to say it may work out cheaper to buy and run a petrol car than a diesel but in pure fuel economy terms a diesel will be better.

In mpg terms you will get better with a diesel, but it's taken a significant change in engine technology from petrol to get that saving.
There is a possibility that where the diesel prices are going the Switft will become the cheaper car to fuel around town though I suspect the diesel will stay best on the open road.

BillScarab

AdrianHi wrote: »

In mpg terms you will get better with a diesel, but it's taken a significant change in engine technology from petrol to get that saving.
There is a possibility that where the diesel prices are going the Switft will become the cheaper car to fuel around town though I suspect the diesel will stay best on the open road.

Totally agree, although the Skoda isn't bad around town wither to be honest. I think the 31mpg is partly due to Little Miss Leadfoot behind the wheel. M

ind you it will be a miracle if the Swift is ever cheaper to run overall as the Octavia is a company car.

Not having to pay any servicing or repair costs makes a huge difference.

anewman

AdrianHi wrote: »

I think it would be down to driving at indicated 80 to 85mph where the fuel economy is probably dropping off fast and the fact that 1/3 of that journey was country lanes with lots of stopping for junctions.

That would probably explain it the gear ratio in 5th in the Skoda gear box isn't too brilliant for economy with fast driving.