MPG and how to improve yours.

[AGFalco]

Yes this is the modern practice with many manufactures, very little engine braking is produced.

 

A hill near me that is not very steep/long is an example, with the car in 3rd gear at the top and doing 30 MPH,

and then using no throttle, but by the time I get to the bottom and still in 3rd gear the Fabia will be doing 60 MPH.

The up side is that because the revs are above 1500 RPM the engine used zero fuel on the way down.

 

An older normally aspirated Peugeot indirect injection diesel I had in the same conditions at the top of the hill

would only reach 45 MPH at the bottom but would be using fuel all the way down.

 

So on a modern car ( Fabia ) you use less fuel by keeping the car IN gear than slipping it in to neutral and coasting.

 

But the REAR brakes on the Fabia are bigger/more efficient than the FRONT brakes were on the old Peugeot.

So the braking power on newer cars are much better than older cars to compensate for the lack of engine braking.

Ventilated disks, ABS, wider tyres with more grip, bigger diameter wheels with bigger brakes inside all help with this.

 

Thanks AG Falco

 

 

[skodaTDI]

Well, we all have our driving styles, can't say there's much of a problem with mine when I return 80+ on a 38 mile trip to work.. the 1.4TDi can give you some okay figures.. the only time it doesn't is when the DPF regen kicks in.. but obviously everyone will get different results when we all have slightly different specs of cars.. it's all been said before.. mpg suffers with bigger wheels, windows open, air con/heating/heated seats, heavy load etc.. etc.. lift and coast (still in gear obviously) on the motorway is probably the best way to get a better mpg and always have the currnent mpg on the trip computer showing so you can see what you are getting..

[Gerrycan]

A small diesel in a light vehicle should give good figures but it is nice to see ovet 80 mpg on a display. Nice one.

 

I would agree it is easier to get good figures on an open road but I am not sure that a motorway will give the best figures.

Personally I have got my best in light urban traffic, 50 to 55 mpg on a long open road journey but upto high 60's in light urban conditions. Purely because speed is restricted and I use that as an advantage. Average speed may be as low as 30kph over a 15klm journey.

The reason our lifetime average is 46 mpg is because I am not the sole driver and we do a lot of very short journeys of less than 3km from cold where it is almost impossible to better 40mpg.

[Gerrycan]

Drafting

The imminent advent of autonomous trucks has resurrected ideas for truck conveys driving nose-to-tail drafting the lead truck to achieve 25% (or more) consumption reductions.

Drafting can also provide benefits for normal drivers but, stating the obvious, carried to tailgating extremes it can be very dangerous and anti-social.

I estimate that travelling at 70mph with normal traffic at 2+ seconds gaps is worth 5 to 10 mpg benefit.

There are still significant benefits at lower speeds particularly if you are behind a truck.

I'm not saying that you should not overtake a slower hgv on a single lane carriageway but if the road is fairly busy and there are more trucks/car in front all doing the same 50 mph speed then there is little time benefit from the maneuver and significant consumptions gains to had from being patient and utilising the truck to improve your consumption.

 

 

 

Edited 6 September, 2017 by Gerrycan

[rum4mo]

I also do the converse - which is driving away from being drafted by trucks travelling closely behind, ie break the tow, that helps a bit obviously.

[Gerrycan]

7 hours ago, rum4mo said:

I also do the converse - which is driving away from being drafted by trucks travelling closely behind, ie break the tow, that helps a bit obviously.

Apart from the obvious danger factor of having someone close behind, especially a truck, there is actually aerodynamic advantage to the one in front.  They are filling in the 'sucking' vortices behind, but obviously the benefits are relatively small.

It has been proven for team time trial cyclists.

[Rooted]

The thing is that it works best when in a smaller vehicle is not close in behind in the 'Eddy' but back where you get the 'Draw', so far enough back that where you can see the HGV, Luton Van or whatevers mirrors and the driver can see you.  (Not in the calm where if raining you need not use your wipers.)

Platooning in HGV's is a very different thing where they are close and the airflow is going across the roofs and not vortexing behind the HGV.

 

Then that further  back position is often where you know you are right because you can lift your foot off the accelerator or if you have a DSG say with 'Coasting function' these days the car disengages gear and you are 'In the Tow'.

 

Sometime speed dependent of the HGV and the height you might be far enough back that some driver will jump in the space between you and the HGV and you have to wait for that BMW/Audi to bog off up the road.

 

 

eg, but this was just Coasting & not while Drafting. But it is useful as an aid to find just where the right drafting position is.

Edited 7 September, 2017 by Headinawayoffski

[rum4mo]

Yes, I only ever move into or stay in at a safe distance behind bigger vehicles, it is a bit confusing to hear that while being the lead vehicle you also benefit from being in a train as I've always felt a slight increase in drag when a bigger vehicle closes up on me from behind, which is why I made the comment about then feeling the need to break away on up the road to get away from towing a truck/bus - obviously more noticeable on an incline.

 

Edit:- back to not needing to use wipers if you sit too close to a truck/bus etc, on my first trip down deep South (South of Londumb) in my VW Passat, I ran out of washer fluid so needed to move into the spray of lorries to get so wetness onto the windscreen as the roads were salty and the sun was out, not good driving with a dry white windscreen - that was when I bought VCDS so that I could enable things like low washer fluid and brake wear - silly Dutch garage did not do that for me!

Edited 7 September, 2017 by rum4mo

[James777]

On 21/08/2017 at 21:52, AGFalco said:

Hi all,

 

I do brim to brim calculations for the MPG and have also compared this to the car's figures.

The car's figures were optimistic until the first service and are now pessimistic? 

 

Most of my mileage is to work and back, but I don't go past a fuel station.

So a fill up happens when I go shopping, about 7 miles from home.

 

The fuel warning light comes on near the 500 mile mark.

So 500 plus miles per tank is the normal at this time of year.

 

The last tank did 572 miles with 5 miles to fill up showing on the car.

Once the fuel warning light comes on, the miles until you need to fill up goes down quicker than the miles actually done!

 

During the last winter it was doing low to mid 50's.

The MFD long term fuel consumption is showing just above 60 MPG at the minute.

 

One bone of contention for me is that both of the cars I run only have a 5 speed gearbox.

But both car engines are available with a 6 speed gearbox in other forms.

 

Gerrycan:  thanks for the link, looks good but still reading it though.

I once went swimming in a pool on the top floor of a Hotel in Adelaide.

I think it is now called the Rydges South Park on South Terrace.

 

Thanks AG Falco

 

 

That is some serious mpg figures! I just don't know how you get them that high long term. I get 50 to 52 on a 7 mile journey to work, long term is crawling up past 44.4 I have covered 16k miles now but the long term is only at 1300 as it was recently  reset. 1.2tsi dsg 110 

Edited 8 September, 2017 by James777

[AGFalco]

OK took some photo's when I got home today.

 

Thanks AG Falco.

[Gerrycan]

That is a very good effort over 2198 miles.

One time I looked at my long-term average when it showed a decent period time on it (I only ever seem to look at it just after it has reset) my average speed was only 18kph (11.5mph) at economy of only 7/100 (40 mpg). The joys of urban driving.

[AGFalco]

Yes I included the average long term speed because this helps with the figures.

It has gone down a little recently, I keep getting caught behind slow moving vehicles. Harvest season.

 

Even followed a tractor once that caught up with another smaller/slower tractor

and the bigger/faster one overtook it on a country road. Impressed.

 

Thanks AG Falco.

[Gerrycan]

The last 3 vehicles I've had from new (two Octavia in there) had the option of viewing 'actual' consumption which I find invaluable for improving technique and finding what works for you in your driving environment and the vehicle characteristics.

Currently we also have an old high mileage, 2003 Toyota Echo (Yaris) manual 1.3L and apart from a couple of trip functions no actual consumption display. My real time average for the 6800km recorded distance is 5.8L/100, just over the official 5.5L/100 combined

Not bad considering it is primarily driven in urban/city areas but I'd guess the lack of an actual real-time consumption is probably costing me up to 0.5L/100. I could get something like a Scanguage but that would not be economically viable.

 

I'm not saying that the displayed consumption is necessarily accurate but it is a good indicator of whether you are wasting fuel or not.

If I drive my Skoda on flat clear 60 kph speed limited road in manual 5th gear then I can maintain that speed with instant consumption showing around 3.6L/100. If I am a little lazy it is easy to apply a little too much throttle and let it creep up to 4.1L/100 and held at that throttle and consumption then the car is imperceptibly accelerating unnecessarily. The rate is so slow that I would have covered several hundred metres at the higher rate before noticing and easing off the throttle to reduce the speed to the limit occurs over a much shorter distance and with less saving than was consumed.

I often use the cruise control in that situation as it is more diligent than I am and more efficient.