Anyone know what Renault claim is the fuel consumption of the Laguna 1.8 
(SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it 
that any 1.8 car I have driven has quite poor fuel consumption?  Is this 
just a bad size for an engine?

"gazzafield"  wrote in message
news:8cudnc-JXuxPVirfRVnyhA@pipex.net...

> Anyone know what Renault claim is the fuel consumption of the Laguna 1.8
> (SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it
> that any 1.8 car I have driven has quite poor fuel consumption?  Is this
> just a bad size for an engine?


Yeah, I've noticed this on a few cars too, mainly in the Cavalier to Mondeo
market. My completely unscientific reckoning for it is that the 1.8 model of
most cars is the compromise model - hasn't got the fuel economy of the 1.6
(or diesel) nor the top end of the 2.0, but is cheaper to buy and insure
than the latter without saying 'poverty spec'. At a guess the gearbox and
some of the engine gubbins are shared with the larger/smaller engined
models, making for less than ideal performance.

Carl Bowman wrote:

> "gazzafield"  wrote in message
> news:8cudnc-JXuxPVirfRVnyhA@pipex.net...
> 
>>Anyone know what Renault claim is the fuel consumption of the Laguna 1.8
>>(SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it
>>that any 1.8 car I have driven has quite poor fuel consumption?  Is this
>>just a bad size for an engine?
> 
> 
> Yeah, I've noticed this on a few cars too, mainly in the Cavalier to Mondeo
> market. My completely unscientific reckoning for it is that the 1.8 model of
> most cars is the compromise model - hasn't got the fuel economy of the 1.6
> (or diesel) nor the top end of the 2.0, but is cheaper to buy and insure
> than the latter without saying 'poverty spec'. At a guess the gearbox and
> some of the engine gubbins are shared with the larger/smaller engined
> models, making for less than ideal performance.
> 
> 


Have to agree.  Hired a Vectra 1.8 once and drove it to Dover via 
Yorkshire from Ayrshire.  Couldn't believe what it cost.  Did a quick 
sum in my head at the petrol station and it was working out at 26 ~ 
27mpg on the motorway!

gazzafield wrote:


> Have to agree.  Hired a Vectra 1.8 once and drove it to Dover via 
> Yorkshire from Ayrshire.  Couldn't believe what it cost.  Did a quick 
> sum in my head at the petrol station and it was working out at 26 ~ 
> 27mpg on the motorway!


One exception is the Passat 1.8. I bought one for my Mum last year and 
found consumption wasn't much worse than my Passat 1.9TD, same age. Mind 
you, it didn't feel much quicker though.

"gazzafield"  wrote in message
news:z4-dndiqbYd9birfRVnysw@pipex.net...

> Carl Bowman wrote:
> > "gazzafield"  wrote in message
> > news:8cudnc-JXuxPVirfRVnyhA@pipex.net...
> >
> >>Anyone know what Renault claim is the fuel consumption of the Laguna 1.8
> >>(SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it
> >>that any 1.8 car I have driven has quite poor fuel consumption?  Is this
> >>just a bad size for an engine?
> >
> >
> > Yeah, I've noticed this on a few cars too, mainly in the Cavalier to
Mondeo
> > market. My completely unscientific reckoning for it is that the 1.8
model of
> > most cars is the compromise model - hasn't got the fuel economy of the
1.6
> > (or diesel) nor the top end of the 2.0, but is cheaper to buy and insure
> > than the latter without saying 'poverty spec'. At a guess the gearbox
and
> > some of the engine gubbins are shared with the larger/smaller engined
> > models, making for less than ideal performance.
> >
> >
>
> Have to agree.  Hired a Vectra 1.8 once and drove it to Dover via
> Yorkshire from Ayrshire.  Couldn't believe what it cost.  Did a quick
> sum in my head at the petrol station and it was working out at 26 ~
> 27mpg on the motorway!


You had a knackered one then- previous shape Vectra's in all petrol flavours
are well known to be capable of 40+ on a motorway run at sensible speeds.

My 1.8 Focus averages between 34-36mpg in mixed driving and will easily
crack 40 on a run.

Tim..

>> Anyone know what Renault claim is the fuel consumption of the Laguna 1.8
>> (SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it
>> that any 1.8 car I have driven has quite poor fuel consumption?  Is this
>> just a bad size for an engine?
>
> Yeah, I've noticed this on a few cars too, mainly in the Cavalier to 
> Mondeo
> market. My completely unscientific reckoning for it is that the 1.8 model 
> of
> most cars is the compromise model - hasn't got the fuel economy of the 1.6
> (or diesel) nor the top end of the 2.0, but is cheaper to buy and insure
> than the latter without saying 'poverty spec'. At a guess the gearbox and
> some of the engine gubbins are shared with the larger/smaller engined
> models, making for less than ideal performance.


All depends on how it's being driven.  Something like a 1.6 Mondeo will 
probably be more economical than a 1.8 Mondeo if you're just doing lots of 
short trips and in lots of stop-start traffic.  But with foot to the floor 
the 1.8 will fare better on the motorway.

30mpg isn't terrible if it's done a fair bit of town work though.  Stop 
whinging, or buy a diesel :-)

Peter

>> Have to agree.  Hired a Vectra 1.8 once and drove it to Dover via 
>> Yorkshire from Ayrshire.  Couldn't believe what it cost.  Did a quick sum 
>> in my head at the petrol station and it was working out at 26 ~ 27mpg on 
>> the motorway!
>
> One exception is the Passat 1.8. I bought one for my Mum last year and 
> found consumption wasn't much worse than my Passat 1.9TD, same age. Mind 
> you, it didn't feel much quicker though.


Mondeo 1.8s aren't bad on fuel in general, and Avensis 1.8s are particularly 
economical.

Peter

In article , gazzafield says...

> Anyone know what Renault claim is the fuel consumption of the Laguna 1.8 
> (SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it 
> that any 1.8 car I have driven has quite poor fuel consumption?  Is this 
> just a bad size for an engine?
> 

DEpends on the car its in. I've found every 2L Ford I've driven whether 
Pinto, Zetec, DOHC Sierra lump, has returned ~32MPG. Got around 40MPG 
out of a 2L Cavvy and ~37 out of both of my 2L Rovers.


-- 
Conor

-You wanted an argument? Oh I'm sorry, but this is abuse. You want room 
K5, just along the corridor. Stupid git. (Monty Python)

gazzafield wrote:

> Anyone know what Renault claim is the fuel consumption of the Laguna
> 1.8 (SOHC) RT Sport?  Mine is working out at approximately 30mpg.
> Why is it that any 1.8 car I have driven has quite poor fuel
> consumption?  Is this just a bad size for an engine?


I get > 30mpg out of my 1.8l car very easily, and can break 40 if I'm
driving steadily.

"gazzafield"  wrote in message
news:8cudnc-JXuxPVirfRVnyhA@pipex.net...

> Anyone know what Renault claim is the fuel consumption of the Laguna 1.8
> (SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it
> that any 1.8 car I have driven has quite poor fuel consumption?  Is this
> just a bad size for an engine?


Depends on the engine, how you drive, the weight of the car, etc.

"gazzafield"  wrote in message 
news:8cudnc-JXuxPVirfRVnyhA@pipex.net...

> Anyone know what Renault claim is the fuel consumption of the Laguna 1.8 
> (SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it 
> that any 1.8 car I have driven has quite poor fuel consumption?  Is this 
> just a bad size for an engine?


I guess that depends on your perspective, but perhaps you've driven lots of 
similar cars over similar routes?

As somebody said, the 1.8 is sometimes the "mid range" four banger with a 
1.6 on the lower side and the 2.0 on the upper side.  It sits between them 
for performance and fuel consumption.  More often, you get fuel consumption 
closer to the 2.0 when driving hard and closer to the 1.6 when being gentle.

In any event, the 1.8 in the early Laguna isn't notable for being economical 
but it has tall enough gearing to be.  My guess would be that you're not 
spending all that long on the motorway?

-- 
The DervMan
www.dervman.com

DervMan wrote:

> "gazzafield"  wrote in message
> news:8cudnc-JXuxPVirfRVnyhA@pipex.net...
> > Anyone know what Renault claim is the fuel consumption of the Laguna 1.8
> > (SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it
> > that any 1.8 car I have driven has quite poor fuel consumption?  Is this
> > just a bad size for an engine?
>
> I guess that depends on your perspective, but perhaps you've driven lots of
> similar cars over similar routes?
>
> As somebody said, the 1.8 is sometimes the "mid range" four banger with a
> 1.6 on the lower side and the 2.0 on the upper side.  It sits between them
> for performance and fuel consumption.  More often, you get fuel consumption
> closer to the 2.0 when driving hard and closer to the 1.6 when being gentle.


But I thought engines were more efficient when worked hard?

In article , 
petermcmillan_uk@yahoo.com says...

> 
> DervMan wrote:
> > "gazzafield"  wrote in message
> > news:8cudnc-JXuxPVirfRVnyhA@pipex.net...
> > > Anyone know what Renault claim is the fuel consumption of the Laguna 1.8
> > > (SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is it
> > > that any 1.8 car I have driven has quite poor fuel consumption?  Is this
> > > just a bad size for an engine?
> >
> > I guess that depends on your perspective, but perhaps you've driven lots of
> > similar cars over similar routes?
> >
> > As somebody said, the 1.8 is sometimes the "mid range" four banger with a
> > 1.6 on the lower side and the 2.0 on the upper side.  It sits between them
> > for performance and fuel consumption.  More often, you get fuel consumption
> > closer to the 2.0 when driving hard and closer to the 1.6 when being gentle.
> 
> But I thought engines were more efficient when worked hard?
> 
> 


More *efficient*, yes.

This means that if pootling along, you're running at 30% efficienty, 
getting 30mpg.

Caning the nuts off it, you're running at 40% efficiency, getting 25mpg. If 
it were less efficient, you may only be getting 20.

Pete.

-- 
NOTE! Email address is spamtrapped. Any email will be deleted
Remove the news and underscore from my address to reply by mail

"Pete Smith"  wrote in message 
news:MPG.1d26636fdb9175d8989738@usenet.plus.net...

> In article ,
> petermcmillan_uk@yahoo.com says...
>>
>> DervMan wrote:
>> > "gazzafield"  wrote in message
>> > news:8cudnc-JXuxPVirfRVnyhA@pipex.net...
>> > > Anyone know what Renault claim is the fuel consumption of the Laguna 
>> > > 1.8
>> > > (SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is 
>> > > it
>> > > that any 1.8 car I have driven has quite poor fuel consumption?  Is 
>> > > this
>> > > just a bad size for an engine?
>> >
>> > I guess that depends on your perspective, but perhaps you've driven 
>> > lots of
>> > similar cars over similar routes?
>> >
>> > As somebody said, the 1.8 is sometimes the "mid range" four banger with 
>> > a
>> > 1.6 on the lower side and the 2.0 on the upper side.  It sits between 
>> > them
>> > for performance and fuel consumption.  More often, you get fuel 
>> > consumption
>> > closer to the 2.0 when driving hard and closer to the 1.6 when being 
>> > gentle.
>>
>> But I thought engines were more efficient when worked hard?
>>
>>
>
> More *efficient*, yes.
>
> This means that if pootling along, you're running at 30% efficienty,
> getting 30mpg.
>
> Caning the nuts off it, you're running at 40% efficiency, getting 25mpg. 
> If
> it were less efficient, you may only be getting 20.



You beat me to it!

-- 
The DervMan
www.dervman.com

wrote in message 
news:1119634592.965883.287000@g49g2000cwa.googlegroups.com...

>
> DervMan wrote:
>> "gazzafield"  wrote in message
>> news:8cudnc-JXuxPVirfRVnyhA@pipex.net...
>> > Anyone know what Renault claim is the fuel consumption of the Laguna 
>> > 1.8
>> > (SOHC) RT Sport?  Mine is working out at approximately 30mpg.  Why is 
>> > it
>> > that any 1.8 car I have driven has quite poor fuel consumption?  Is 
>> > this
>> > just a bad size for an engine?
>>
>> I guess that depends on your perspective, but perhaps you've driven lots 
>> of
>> similar cars over similar routes?
>>
>> As somebody said, the 1.8 is sometimes the "mid range" four banger with a
>> 1.6 on the lower side and the 2.0 on the upper side.  It sits between 
>> them
>> for performance and fuel consumption.  More often, you get fuel 
>> consumption
>> closer to the 2.0 when driving hard and closer to the 1.6 when being 
>> gentle.
>
> But I thought engines were more efficient when worked hard?



Efficiency isn't the same as economical..

-- 
The DervMan
www.dervman.com

Pete Smith wrote:

> In article ,
> petermcmillan_uk@yahoo.com says...
> >
> > But I thought engines were more efficient when worked hard?
> >
> >
>
> More *efficient*, yes.
>
> This means that if pootling along, you're running at 30% efficienty,
> getting 30mpg.
>
> Caning the nuts off it, you're running at 40% efficiency, getting 25mpg. If
> it were less efficient, you may only be getting 20.


To get a car to move you need to accelerate, which generally drinks a
considerable amount of fuel.  If you are pootling along then you may
spend say 30 seconds under light accleration before reaching an
economical cruise speed.  If you are 'Caning the nuts off it' then you
may spend 15 seconds before reaching a cruise speed.

I was under the impression that working the engine hard used the least
fuel.  Somebody said a while ago that for the fuel economy cycles they
probably thrash it to get the best results.  I'm confused now anyway.

wrote in message 
news:1119693076.953238.100200@g47g2000cwa.googlegroups.com...

>
> Pete Smith wrote:
>> In article ,
>> petermcmillan_uk@yahoo.com says...
>> >
>> > But I thought engines were more efficient when worked hard?
>> >
>> >
>>
>> More *efficient*, yes.
>>
>> This means that if pootling along, you're running at 30% efficienty,
>> getting 30mpg.
>>
>> Caning the nuts off it, you're running at 40% efficiency, getting 25mpg. 
>> If
>> it were less efficient, you may only be getting 20.
>
> To get a car to move you need to accelerate, which generally drinks a
> considerable amount of fuel.  If you are pootling along then you may
> spend say 30 seconds under light accleration before reaching an
> economical cruise speed.  If you are 'Caning the nuts off it' then you
> may spend 15 seconds before reaching a cruise speed.

> I was under the impression that working the engine hard used the least
> fuel.


How, exactly?  The fuel an engine burns is directly proportional to the 
amount of power it produces.


> Somebody said a while ago that for the fuel economy cycles they
> probably thrash it to get the best results.  I'm confused now anyway.


Clearly!

It's a complicated scenario to try to model but if we suppose that at a 
given cruising speed the engine requires 50% of maximum power.  To 
accelerate to this speed we must use at least 50%.  If we use 50% maximum 
power we'll extend the acceleration over a very big distance and over many 
time units, _then_ we'll be cruising.  if we use 100% of the power we'll be 
accelerating for as short as possible over fewer time units.

The question is: is accelerating at 100% more economical over the overall 
distance than accelerating at a higher rate before cruising.

Once cruising the rate of power production is constant, so is it more 
economical to use 100% of maximum power and engine speed or is there a 
better compromise.

You'll find that many petrol engines can deliver a sizeable chunk of their 
best performance and only use around two thirds to three quarters of maximum 
engine speed and throttle.

Our cruise control system manages the balance between relatively decent 
acceleration and decent economy.  It uses a maximum of around sixty percent 
throttle under most circumstances.

In my experience, taking it to the redline in every gear until you reach the 
cruising speed is less economical than a more rate of acceleration.

-- 
The DervMan
www.dervman.com

wrote in message
news:1119693076.953238.100200@g47g2000cwa.googlegroups.com...

>
> Pete Smith wrote:
> > In article ,
> > petermcmillan_uk@yahoo.com says...
[snip]
> To get a car to move you need to accelerate, which generally drinks a
> considerable amount of fuel.  If you are pootling along then you may
> spend say 30 seconds under light accleration before reaching an
> economical cruise speed.  If you are 'Caning the nuts off it' then you
> may spend 15 seconds before reaching a cruise speed.
>
> I was under the impression that working the engine hard used the least
> fuel.  Somebody said a while ago that for the fuel economy cycles they
> probably thrash it to get the best results.  I'm confused now anyway.


Did you wag physics at school?

When a mass is stationary it will take more effort to move it, once it's
moving then a vehicle will use less fuel , if your assumption was correct
everyone would thrash their car from standstill for better economy (not true
I'm afraid) accelerate as gently as possible for best fuel efficiency, I get
mid 30s mpg from a 2L turbo car.

The message 
from petermcmillan_uk@yahoo.com contains these words:


> I was under the impression that working the engine hard used the least
> fuel.  Somebody said a while ago that for the fuel economy cycles they
> probably thrash it to get the best results.  I'm confused now anyway.


Mileage freaks - the ones who do 2500+mpg in things that look like
cigars on wheels - use the coast and burn technique where they work a
tiny engine (10cc or less, often) at full throttle to acheive a
particular speed, then coast with the engine off until they drop to the
lowest speed allowable in the competition, then accelerate again.

This works because the engines are indeed at their most efficient at
full throttle, and for their particular setup this is fine.

However, in real life it just doesn't work. For one thing you'd be way
over the speed limit most of the time, or you'd be thrashing along in
1st gear wasting vast amounts of energy because the engine's very
wasteful at high revs.

-- 
Skipweasel.
Ivor Cutler - "Never knowingly understood."