Question about engine size and fuel economy

[adolf hamster]

Diesels don't have throttles.

True, and the difference in compression ratio is also a cause for diesels naturally getting better mpg than petrols (hence their massive popularity in recent years)

But thats the generic theory behind why manufacturers are moving towards smaller engines and why small engine big turbo is good in a lab but not so good in the real world.

One thing i do wonder these days is if people appreciate that mpg is only part of a cars total emissions, and that making cars with so much tech that when it breaks people just scrap the car is as good a notion as making cars that can be repaired indefinately/last a lot longer.

The old delivery milage prius has more co2 to its name than a 20 year old defender argument.

 

[Lokken86]

You really do have to drive like a granny to get close to the rated mpg but it is possible and it's not fun (To do all the time).

 

[Six6siX]

It disappoints me greatly that the most of the discussions I have about motoring these days are no longer about performance, dynamics, driving enjoyment etc but rather mpgz and economy - even with people who are supposedly petrol heads - which is even more bizarre to me! I just don't 'get' it and can't see the attraction with anything to do with this shift to super economical motoring.

 

[robj20]

It disappoints me greatly that the most of the discussions I have about motoring these days are no longer about performance, dynamics, driving enjoyment etc but rather mpgz and economy - even with people who are supposedly petrol heads - which is even more bizarre to me! I just don't 'get' it and can't see the attraction with anything to do with this shift to super economical motoring.

How can you not get it. It costs a lot more than just 10 years ago to fuel and run a car, so of course people want to keep the costs as low as possible.

 

[Six6siX]

How can you not get it. It costs a lot more than just 10 years ago to fuel and run a car, so of course people want to keep the costs as low as possible.

For most people, I doubt the biggest cost over their ownership is fuel - its more likely the car itself, insurance and depreciation.

People still spent money on fuel 10 years ago and proportionally it may have risen a bit but so what? Why does that mean all other aspects of motoring have dwindled into irrelevance? The obsession has driven the industry to the point where no (very few) car manufacturers are interested in producing a decent engine or a car that does anything other than deliver 10 billion mpg. But only on paper.

So yeah, I don't get it.

 

[adolf hamster]

It disappoints me greatly that the most of the discussions I have about motoring these days are no longer about performance, dynamics, driving enjoyment etc but rather mpgz and economy - even with people who are supposedly petrol heads - which is even more bizarre to me! I just don't 'get' it and can't see the attraction with anything to do with this shift to super economical motoring.

its a sign of the times, if you do any kind of commuting it doesn't take much distance to get your fuel bill into thousands per year, and being one of the more directly observable costs of motoring people worry about it a lot.

thing is, people still want power, but they want mpg too, and the motor industry has pandered to that leaving us with tiny engines with massive turbos that have the numbers on paper all right, but don't make too much sense in the real world.

 

[Scania]

I suspect a lot of cars doing 60 by there speedo is about 56 actual anyway, i know mine is.

Very true hence my point about tachographs being calibrated and car speedometers not, I often pass cars with digital dash's @ 55mph to see their speed reading ~ 60mph.

 

[theone8181]

I ignore mpg to some extent, i get about 22 normal driving or 35 on the motorway, however i'd rather be driving a supercar than a crappy diesel or a piddly small engined city car.

 

[Nasher]

I've never had a car that actually got the advertised MPG with normal driving. It's been proven that they cheat when testing by doing things like taping over panel gaps, using a lower power engine map, doing it at high altitude, etc.

 

[Alibaba99]

True, and the difference in compression ratio is also a cause for diesels naturally getting better mpg than petrols (hence their massive popularity in recent years)

But thats the generic theory behind why manufacturers are moving towards smaller engines and why small engine big turbo is good in a lab but not so good in the real world.

One thing i do wonder these days is if people appreciate that mpg is only part of a cars total emissions, and that making cars with so much tech that when it breaks people just scrap the car is as good a notion as making cars that can be repaired indefinately/last a lot longer.

The old delivery milage prius has more co2 to its name than a 20 year old defender argument.

Diesel's much higher calorific value also contributes to the economy as well. WEC balances the car on energy usage and the Audi, therefore, gets less fuel.

 

[Liquidfox]

My rule of thumb is to look at the Urban figure, (ignore combined/extra-urban) and that will give you an idea of what you might expect on good day for an extended A-road / motorway run. Our car has never, ever hit the combined figure (never mind extra-urban) under any conditions

I wouldn't agree with that, the figures for mine are:
Urban mpg 20.9 mpg
Extra Urban mpg 41.5 mpg
Average mpg 30.4 mpg

Urban you'd be lucky to see 16, combined of 30 is about right for motorway journeys (I get 33-36) and good luck ever hitting 41.5. I managed 39MPG sat at 60mph for 4 hours straight, by god it was the most boring drive I've ever done. It was probably the most tiring too due to the amount of concentration required to feather the throttle.

 

[robj20]

I wouldn't agree with that, the figures for mine are:
Urban mpg 20.9 mpg
Extra Urban mpg 41.5 mpg
Average mpg 30.4 mpg

Urban you'd be lucky to see 16, combined of 30 is about right for motorway journeys (I get 33-36) and good luck ever hitting 41.5. I managed 39MPG sat at 60mph for 4 hours straight, by god it was the most boring drive I've ever done. It was probably the most tiring too due to the amount of concentration required to feather the throttle.

What, no cruise control?

 

[ttaskmaster]

For most people, I doubt the biggest cost over their ownership is fuel - its more likely the car itself, insurance and depreciation.

And speeding tickets, in all those NSLs that they keep dropping down to flippin' 20mph zones....!!

TBH, I think a lot of that has been driven by the older folk, as we're all grown up now and have learned to be careful with our money.
Since we were blasting round and burning petrol at only 40p per litre back in 1984, seeing it over three times that in 2014 (139p per litre, no kidding) kinda scares you back into economy mode.

Then, of course, you stop at the motorway services and their prices give you a heart attack!!

 

[Dr Who]

On the motorway? Enjoy those artics overtaking you as close as possible.

Really annoys me this, as you doing 60 forces large vehicles into the middle lane just to keep their momentum up and thus turning a 3 lane road into a 1 lane for 30 secs minimum, and repeatedly, until the truck(s) gets past.

Just to save a few precious pennies.

Artics are restricted to 56mph, and legally limited to 60.

I have sat at 60 in lane 1 and the only thing that has overtaken me is centre lane hoggers

 

[Dr Who]

I've never had a car that actually got the advertised MPG with normal driving. It's been proven that they cheat when testing by doing things like taping over panel gaps, using a lower power engine map, doing it at high altitude, etc.

You can do it without cheating

http://www.lifehacker.co.uk/2014/06/26/hypermile-driving-secrets-max-petrol-mileage

There is little more satisfying that driving around town and never stopping at lights because they are green by the time you get there. Makes a huge difference to your fuel consumption as well. can lose 2-3mpg at every set of lights you stop at and have to accelerate away from.

 

[Dr Who]

http://lifehacker.com/does-speeding-really-get-you-there-any-faster-1556767685

This details the paradigm shift you need to enable slower more economic driving.

 

[Entai]

I've never had a car that actually got the advertised MPG with normal driving. It's been proven that they cheat when testing by doing things like taping over panel gaps, using a lower power engine map, doing it at high altitude, etc.

Ummm

ALL testing of fuel efficiency figures, is done indoors on a rolling road, with a car that had been bought from a dealers, NOT supplied by the manufacturers so all your so called "cheats" are null and void.

I know because we do the testing where I work.

 

[Alibaba99]

Ummm

ALL testing of fuel efficiency figures, is done indoors on a rolling road, with a car that had been bought from a dealers, NOT supplied by the manufacturers so all your so called "cheats" are null and void.

I know because we do the testing where I work.

Do you also go out and measure the rolling resistance of the car to set the rolling road up, or are those figures supplied by the manufacturer?

If they've come from the manufacturer then they are open to manipulation in a whole multitude of ways.

 

[Entai]

All settings are generic as it is a generic test.

 

[MORE SPEED]

Ummm

ALL testing of fuel efficiency figures, is done indoors on a rolling road, with a car that had been bought from a dealers, NOT supplied by the manufacturers so all your so called "cheats" are null and void.

I know because we do the testing where I work.

How does this work, as figures are published before a car goes on sale?