what speed to achieve best mpg?

[Phil's Barber]

If sitting behind HGV's is the only way you can afford to run your car, you should definitely consider another car.

I'm not sure where I said it's the only way I can afford to run my car. My post was a response to the thread title. It was based on the result of an experiment to see how many miles I could stretch out of a tank of diesel.

Do you know what a troll is?

 

[Boydie]

50-60 with a bit of free wheeling got me 61mpg today over 70miles - i honestly could not believe it!!! :O

 

[Amchlolor]

I'm not sure where I said it's the only way I can afford to run my car. My post was a response to the thread title. It was based on the result of an experiment to see how many miles I could stretch out of a tank of diesel.

How bored/stupid to you have to be to slipstream trucks as an experiment?
You have to be pretty damned close to benefit from 'clean' air.
Too far back and all you'll get is buffeting.
The closer you are to the truck, the less you can see and the less time you'd have to brake.
So you'll have to forgive me for thinking it's a bit of an idiotic experiment.

 

[Iggu]

If you get close enough to the truck you could maybe throw a grappling hook onto it and travel for free. Naff thread this - there's too much made of fuel costs. Even now its still the cheapest way to get about and even if you rag it for fun its cheaper than a beer in the pub. Just pay it and enjoy the drive.

 

[Phil's Barber]

How bored/stupid to you have to be to slipstream trucks as an experiment?
You have to be pretty damned close to benefit from 'clean' air.
Too far back and all you'll get is buffeting.
The closer you are to the truck, the less you can see and the less time you'd have to brake.
So you'll have to forgive me for thinking it's a bit of an idiotic experiment.

FYI An Internet troll, or simply troll in Internet slang, is someone who posts controversial and usually irrelevant or off-topic messages in an online community, such as an online discussion forum or chat room, with the intention of baiting other users into an emotional response[1] or to generally disrupt normal on-topic discussion.[2]

Fits the bill if you ask me. For the record your opinion on how and what I drive means nothing to me, so save your energies troll.

 

[Amchlolor]

FYI An Internet troll, or simply troll in Internet slang, is someone who posts controversial and usually irrelevant or off-topic messages in an online community, such as an online discussion forum or chat room, with the intention of baiting other users into an emotional response[1] or to generally disrupt normal on-topic discussion.[2]

Fits the bill if you ask me. For the record your opinion on how and what I drive means nothing to me, so save your energies troll.

In what way is questioning your fuel saving madness, in a fuel saving thread, irrelevant or off-topic?

Slipstreaming trucks is the most ridiculous admission I've read on this forum, ever.

Well done.

 

[Iggu]

Couldn't agree more. Preposterous.

 

[sleep envy]

I find using the cruise control helps to obtain better MPG

it minimises the turbo spooling up and having a bigger slurp of diesel

 

[lil_coz]

I find using the cruise control helps to obtain better MPG

it minimises the turbo spooling up and having a bigger slurp of diesel

Really? I find that using the cruise uses more fuel than me using my own foot. If I wanted an economical drive I'd probably stick to 60. Also you may want to watch the episode of Top Gear where Clarkson takes an A8 from London to Edinburgh and back on 1 tank.

Coss

 

[Amchlolor]

I took a colleague's petrol Golf to Manchester and back, not so long ago.
It has cruise.
Used cruise on the way down, but it felt weird.
Like the car was definitely using more throttle than it really needed, for the speed.
Didn't bother way it on the way home, sure enough we got better MPG.
It seems to me that cruise just decides on a 'set' throttle opening, where your brain/foot can constantly adjust and back off the throttle, whilst maintaining the same speed.

 

[lil_coz]

It seems to me that cruise just decides on a 'set' throttle opening, where your brain/foot can constantly adjust and back off the throttle, whilst maintaining the same speed.

Exactly

 

[sat1983]

I can easily see that my car is giving better MPG in 5th, rather than 6th, at speeds under 85mph.
Without the gauge, you'd just whack it into 6th and 'assume' it was better.

I had always assumed 6th was there to be the most economical gear on the motorway. That is very interesting. Any theory as to why 5th would be more economical?

 

[benw123]

I had always assumed 6th was there to be the most economical gear on the motorway. That is very interesting. Any theory as to why 5th would be more economical?

The engine probably isn't working as hard to turn the gearbox in sixth gear - I posted this earlier. Imagine riding a mountain bike in top gear and the amount of effort it might take. Drop down a few cogs and it becomes easier so you travel faster.

 

[sat1983]

True enough Ben, will give this a go. Why a 6th gear though?

 

[Amchlolor]

I had always assumed 6th was there to be the most economical gear on the motorway. That is very interesting. Any theory as to why 5th would be more economical?

For my car, it's because 5th is right in the 'meaty part' of the engine's torque range, so I can hold the speed on the merest whiff of throttle.
Changing to 6th makes the revs drop to the bottom of the torque band, so I have to use much larger throttle openings to react to stuff like hills, traffic, wind etc.
Once I'm over 85mph, 6th is in the 'meaty part' again, so it becomes valid.

 

[sat1983]

Yep sure does make sense bowfer. I sure have learnt something new today!

 

[boggysv]

Bowfer, I suppose that only applies to your car(diesel)?

Cant remember the exact figure, but wont motorway speeds in 5th gear be around the 4krpm region for the S3? How can that be more economical?

Not to mention the exhaust noise becoming unbearable after an hour or so.

 

[Fast,not furious]

Going back to cruise....i had a 2.0 FSI se,and after experimenting on quiet stretches of motorway,as well as busy,and varying the set speed,i concluded that fuel economy was better with cruise switched off.

Another point.....you need to concentrate more with cruise on...as my ex discovered after stuffing her BM into the back of a truck!!

 

[Amchlolor]

Another point.....you need to concentrate more with cruise on...

That I can't agree with.
I've used cruise in all sorts of cars, I always found it a piece of p*ss to use.
As soon as you dab the brakes, the cruise switches off.
Then just press 'resume' to get back up to speed.
Easy peasy.
I also like the way it means you can concentrate on the road ahead, rather than constantly looking at your speedo, so I actually find it makes for more relaxing drive.
The only time I felt cruise struggled was in my colleague's 1.6Fsi Golf.
It just didn't have the power/torque to cope with cruise, so I just switched it off and reverted back to revving the tats off it.

 

[sleep envy]

It seems to me that cruise just decides on a 'set' throttle opening, where your brain/foot can constantly adjust and back off the throttle, whilst maintaining the same speed.

not too sure about that one otherwise on the flat it would accelerate away and on an incline it would slow down

my A3 maintains it's set speed and automaticaly adjusts the throttle whether it needs to open or close dependent on the road

it's very evident on a decent as you'll feel the engine pick up and die every 2 or 3 seconds to check the required throttle opening

 

[Boydie]

I just got 570miles from one tank - well chuffed!

 

[lil_coz]

it's very evident on a decent as you'll feel the engine pick up and die every 2 or 3 seconds to check the required throttle opening

Its because of this constant checking that it uses more fuel where as if it were your own foot, you'd be off it until you reach the bottom of a hill. Also the way cruise sets about going up the hill, you can feel it pin you in the seat. Its a very aggressive acceleration which again, uses more fuel.

 

[consilio]

Its because of this constant checking that it uses more fuel where as if it were your own foot, you'd be off it until you reach the bottom of a hill. Also the way cruise sets about going up the hill, you can feel it pin you in the seat. Its a very aggressive acceleration which again, uses more fuel.

The car does not need to use the engine every 2-3 seconds to check the speed. The car knows exactly what speed the car is doing at all times, and whether the speed is increasing or decreasing. If above the cruise speed setting, no throttle is applied, if below, throttle is applied.

Also when accelerating, i reckon its only on about 20-30% max load. I am pinned to the seat noticably if I put my foot down whilst cruise is already accelerating.

Maybe you have a fault?

 

[TFSI]

Normal cruise usage will return reasonable fuel on flat running but disabling and hitting resume will bang your throttle wide open and drink fuel. We have a facility on the trucks called a driver speed limiter as well as the legislation speed limiter (56 mph).
The driver can set this himself anywhere between 20-56 mph and then drive on the throttle pedal and at his chosen speed it just runs out of steam.
We have found the driver RSL returns slightly better fuel than cruise and if he selects manual from full auto he can make the gearbox hold its gears longer on hill climbs rather than shifting down and loosing road speed as most auto boxes do.

Its just like DSG and its in a 44 ton truck along with LED driving lights, Audi style dash, chromed front grill, ESP, ABS, ASR, EBS, ECAS, EDC and AS Tronic, KSM

Bet you didn't know your prestige car maker has done alot of styling work on a big ugly 44ton truck.

I chuckle at the A5 drivers when they see a truck coming the other way with LED tube lights on that look a damn site better than their A5 tat.

The road to good MPG revolves keeping the throttle completely shut as much as possible.

 

[lil_coz]

The car does not need to use the engine every 2-3 seconds to check the speed. The car knows exactly what speed the car is doing at all times, and whether the speed is increasing or decreasing. If above the cruise speed setting, no throttle is applied, if below, throttle is applied.

Also when accelerating, i reckon its only on about 20-30% max load. I am pinned to the seat noticably if I put my foot down whilst cruise is already accelerating.

Maybe you have a fault?

No fault at all. I've always found this to be the case. Same as a few other people on here agree with me so I doubt its a mass problem with all cruise controls. I once saw a test that was done where they drove the same car the same distance along the same stretch of road. The first test was to drive the car over the distance by foot at a constant mpg. They then took the average speed of the car during that test and went back to the start and set the cruise control to that speed. The result was a lower mpg figure.

I've tried this out a few times in my car too from J11 to J19 on the M1. Steady 70mph by foot ALWAYS resulted in higher mpg figures when the same trip was done with cruise at 70.

 

[lanky512]

If you get close enough to the truck you could maybe throw a grappling hook onto it and travel for free. Naff thread this - there's too much made of fuel costs. Even now its still the cheapest way to get about and even if you rag it for fun its cheaper than a beer in the pub. Just pay it and enjoy the drive.

Couldn't agree more, Pay it and enjoy Iv tried driving slow and it bores me to death. I base my fuel comsumption on 60 miles out of 10 quids worth (petrol), if i get this its all good but most of the time i just forget about it and wait for the light to come back hehe.