Improving fuel economy of bigger and smaller vehicles

[ajlelectronics]

Here's a gem...

We have (yet again) roadworks on the A48 and temporary traffic lights on a short incline. I went out with 'er indoors on Saturday and when stopped at the lights, she was holding the car stationary on the incline by slipping the clutch. "But I always do that". I tried to explain about the fuel use, never mind stuffing the clutch plate but could see the glass wall come down so I gave up.

 

[Edward Teach]

Here's a gem...

We have (yet again) roadworks on the A48 and temporary traffic lights on a short incline. I went out with 'er indoors on Saturday and when stopped at the lights, she was holding the car stationary on the incline by slipping the clutch. "But I always do that". I tried to explain about the fuel use, never mind stuffing the clutch plate but could see the glass wall come down so I gave up.

Use her car,
Burn the clutch out,
I told you so

 

[Greeves246]

I agree with 8ob. Most people today have no sense of anticipation, learning to ride and drive in the 1960s when everything had drum brakes and no power you had to drive smoothly. Jackie Stewart said coming off the throttle gently was as important as pressing it gently to make for quick driving especially in the wet. Even truer on a bike when tyres lasted 20,000 miles they were so hard.

 

[ajlelectronics]

Use her car,
Burn the clutch out,
I told you so

I don't think that you can be married Edward, it doesn't work like that.

 

[ajlelectronics]

Even truer on a bike when tyres lasted 20,000 miles they were so hard.

I can only dream about such mileages. I struggle to get more than 4-5K from my rear tyre and they are piggin' expensive, with only three tyres rated appropriately. As a result, I tend to practice smooth riding besides the safety aspect.

 

[stuvy]

I’m back to commuting 30 mins each way in my discovery 3.9 v8 I just fill it up and listen to the glorious soundtrack

On the upside summers coming quicker for you lot

 

[Greeves246]

I can only dream about such mileages. I struggle to get more than 4-5K from my rear tyre and they are piggin' expensive, with only three tyres rated appropriately. As a result, I tend to practice smooth riding besides the safety aspect.

I used to get a full season out of a pair of Dunlop Triangulars on my Norton and that included the Irish roads and the Manx Grand Prix! Now they last a race or two laps on the Island.

 

[Aerohead]

How to get terrible fuel efficiency:

Cold starts: In USA we have a GMC Suburban with an injected 454 7.4L V8, at -30C it can swallow a gallon or more just warming up the 30L cooling system without moving.
Often +5C starts in a small car in the UK then short trips kills fuel economy

Always ring it out to the redline before shifting!

Combine number 2 above with wait until the last minute to brake right at the edge of ABS activation. Do this on say Nurenburg ring (2&3) and a 40mpg car at 60mph with powerful engine can transform to a 4mpg car

 

[Justme]

So, what if you "drove like a granny"



Why did you need to put in that caveat?

If blanket coasting always cost more fuel than not, you wouldn't need such caveats.

I'm pretty sure we do agree that coasting *can* result in an increase in mpg but that to use it effectively isn't straightforward, definitely dangerous and even maybe illegal.

NOTHING is ALWAYS

You wanted the multi hill gaining speed to get over the next one caveat ...

Get the conditions right & of course it could save fuel.
How often do those condition actually happen in real driving?
If your able to gain speed on the down hill then you are driving like a granny & being a road hazard.
Driving to slow = bad
Coasting (clutch down or out of gear) = bad
Driving with a fluctuating speed = bad
driving engine off = bad

Even if there are some very rare conditions when you might save a little fuel there is never a time you should be doing so for safety reasons.
Safety always trumps fuel saving.

 

[Justme]

Simply closing the throttle early enough doesn’t wear anything out.

I find rolling down long gradients behind cars, while they all have brake lights on, I have to give a whiff of throttle, even in top gear, or I am slowing down more than they are.

Sorry I shortened the reply.

Yes just gently lifting off in a controlled over run way will minimise wear.

Lots change down at a high speed & virtually dump clutch so that the engine redlines & speed drops dramatically.

Using heavy engine retardation.

Using the correct gear for the speed to bracket the usable speed is totally fine.

 

[Justme]

Simply closing the throttle early enough doesn’t wear anything out.

I find rolling down long gradients behind cars, while they all have brake lights on, I have to give a whiff of throttle, even in top gear, or I am slowing down more than they are.

Is your vehicle petrol or Diesel?

 

[Gareth J]

NOTHING is ALWAYS

You wanted the multi hill gaining speed to get over the next one caveat ...

Get the conditions right & of course it could save fuel.
How often do those condition actually happen in real driving?
If your able to gain speed on the down hill then you are driving like a granny & being a road hazard.
Driving to slow = bad
Coasting (clutch down or out of gear) = bad
Driving with a fluctuating speed = bad
driving engine off = bad

Even if there are some very rare conditions when you might save a little fuel there is never a time you should be doing so for safety reasons.
Safety always trumps fuel saving.

Safety does *generally* (not always, remember, "NOTHING is ALWAYS") trump fuel saving, I agree. But for the purposes of the discussion, it is possible to save fuel by coasting, even in a modern car, even if the conditions that need to be met are rare or unsafe. A blanket *never happens* is silly and that's what I took issue with.

 

[Gritineye]

I’m back to commuting 30 mins each way in my discovery 3.9 v8 I just fill it up and listen to the glorious soundtrack

On the upside summers coming quicker for you lot

Back in the 80s I had a Series 1 LR 86, bog standard 1600 engine got around 15 mpg on a very good day.

Then I built and fitted a modded Rover V8 210 bhp on the dyno, mid range cam, gobs of torque, 3.5:1 diffs, overdrive and radial tyres. True top speed achieved slip steaming an Opel Senator, 110 mph!

Wasn't bothered about mileage back then but everyone was telling me the mileage must be awful.

So when my daily round trip to one job site with all my gear in it was around 70 miles, mixed A roads, dual carriage way, B roads, and couple of miles unclassified with speed bumps, in a nice summer period no wind to speak of, I did an experiment.

First tank full I drove like a saint, feather light right foot and hardly ever braking, but keeping up with traffic, calculated mpg at fill up, 27 mpg.

Second tank full I gave it the full loony teenage technique that I was still fearless enough to do, got 15 mpg.

So I reckon a slippery vehicle, restrained driving style and a perfectly tuned engine have to be the most important things in all this mpg malarky.

 

[stuvy]

Back in the 80s I had a Series 1 LR 86, bog standard 1600 engine got around 15 mpg on a very good day.

Then I built and fitted a modded Rover V8 210 bhp on the dyno, mid range cam, gobs of torque, 3.5:1 diffs, overdrive and radial tyres. True top speed achieved slip steaming an Opel Senator, 110 mph!

Wasn't bothered about mileage back then but everyone was telling me the mileage must be awful.

So when my daily round trip to one job site with all my gear in it was around 70 miles, mixed A roads, dual carriage way, B roads, and couple of miles unclassified with speed bumps, in a nice summer period no wind to speak of, I did an experiment.

First tank full I drove like a saint, feather light right foot and hardly ever braking, but keeping up with traffic, calculated mpg at fill up, 27 mpg.

Second tank full I gave it the full loony teenage technique that I was still fearless enough to do, got 15 mpg.

So I reckon a slippery vehicle, restrained driving style and a perfectly tuned engine have to be the most important things in all this mpg malarky.

Mines an auto, if I boot it around town I can drop 1/4 of a tank in 15 mins

If I drive my mx5(1.8) hard I can get the same mpg from the disco so not gonna worry about it

Iv only aimed for 100 miles from a motorbike as I never worry about it, it’s nice to be in first name terms with the chap at the petrol station

 

[Morrisman]

Is your vehicle petrol or Diesel?

Petrol, the bike is.

My Mondeo is diseasel. I get 50mpg from each.

 

[Morrisman]

Sorry I shortened the reply.

Yes just gently lifting off in a controlled over run way will minimise wear.

Lots change down at a high speed & virtually dump clutch so that the engine redlines & speed drops dramatically.

Using heavy engine retardation.

Using the correct gear for the speed to bracket the usable speed is totally fine.

Not long ago someone mentioned engine braking in a truck, and how they’d burned out the clutch in a single trip. The idea is not to use the clutch as a brake, but to match engine speed to the gear, before gently releasing the clutch.

 

[Gritineye]

Mines an auto, if I boot it around town I can drop 1/4 of a tank in 15 mins

If I drive my mx5(1.8) hard I can get the same mpg from the disco so not gonna worry about it

Iv only aimed for 100 miles from a motorbike as I never worry about it, it’s nice to be in first name terms with all the chaps at all the petrol stations.

Fixed that for ya :-)

I was the same when I owned a petrol engined Scammell Explorer, 3 mpg

 

[stuvy]

Fixed that for ya :-)

I was the same when I owned a petrol engined Scammell Explorer, 3 mpg

My Sierra sapphire did 4mpg but that was 520bhp at the rear wheels….

 

[fizzy]

Manuals give better fuel economy than autos if you drive them properly.
Modern autos are better than the older types but you can still save a few mpg compared to even the best autos.
With identical Audis and Insignias etc - same engine same model etc I found about 4mpg better in a manual. I do drive quite hard though.
With older autos you can be looking at 10mpg difference. Mate had a Nissan Navarra pickup. He was getting 20mpg out of the auto and 30 mpg out of the manual version.
Same with the older Discovery.

 

[atomant48]

My Sierra sapphire did 4mpg but that was 520bhp at the rear wheels….

That sounds like a hell of a lot of fun. My teslas only got half that at the rear wheels. But about the same at the front :-)

But it’s far too “safe” in its delivery to be proper fun!