Real life mpg petrrol and diesel

[derelyth]

Dean,

A run from Fareham to Guildford on Xmas Eve (~50miles at 65):

I know the OBC figs are a bit optimistic but I was still pleasantly surprised!

Sent from my Nexus 4 using Tapatalk

 

[trekmeister]

I can get 60+mpg in a mapped 140 bkd on a straight run @55mph in ambient conditions

 

[skidpan]

Ignoring official MPG figures, in my experience of driving various cars so far I have noticed that two identical cars but one with a petrol and the other with the nearest equivalent on power diesel will normally show 5 mpg more for the diesel in the same driving conditions. When you factor in the prices difference at the pumps the diesel loses 2 mpg from its advantage.

Am I the only one that experiences this? It's one of the main reasons I am going back to petrol. I haven't driven the 150 tdi but if the 1.4 TSI achieved 45 mpg I reckon the 150 tdi would only get 50 mpg in the same driving conditions.

My last car was a BMW 118D. Over the 5 1/2 years I owned it the average fuel consumption was 48 mpg. The Leon 1.4 TSi has averaged 45 mpg in the 6 months I have owned it using it in exactly the same way, same commute etc.

At 8 pence a litre between petrol and diesel the corrected mpg for the Leon would be 47.8 mpg this my fuel costs have not changed.

Before I settled on the 1.4 TSi I did consider the 150 PS diesel Leon. Looking on various forums and Honest John Real MPG's people appeared to be getting about 53 mpg form it as opposed to the 45 mpg they were getting from the 1.4 TSi. Even taking into account the fact that the 150 PS would be worth bit more than a 1.4 TSi the break even point was way beyond the 50,000 miles max I do in car and I also preferred the way the 1.4 TSi drove, much smoother power delivery.

The mpg I quote for the BMW and Leon are real calculated figures and noit the nonsense shown by the dash display.

I can get 60+mpg in a mapped 140 bkd on a straight run @55mph in ambient conditions

Totally irrelevant. If the road was downhill with a following wind anything is possible.

Its averages that matter not the best you have seen in one particular circumstance.

 

[DeanC]

Dean,

A run from Fareham to Guildford on Xmas Eve (~50miles at 65):

I know the OBC figs are a bit optimistic but I was still pleasantly surprised!

Sent from my Nexus 4 using Tapatalk

That's pretty good mate, 1.8? can't see your sig on tapatalk.

 

[DeanC]

Dean,

A run from Fareham to Guildford on Xmas Eve (~50miles at 65):

I know the OBC figs are a bit optimistic but I was still pleasantly surprised!

Sent from my Nexus 4 using Tapatalk

Mine at mainly 70mph round the m25 with the 50mph bit at watford and some slow traffic at heahrow.

Best I've had is 76mpg on a clear run at 70 and 50. I find the trip is about 5% out.

 

[derelyth]

That's pretty good mate, 1.8? can't see your sig on tapatalk.

Yep - FR DSG with only 1400 miles on the clock.

Sent from my Nexus 4 using Tapatalk

 

[DeanC]

Yep - FR DSG with only 1400 miles on the clock.

Sent from my Nexus 4 using Tapatalk

Amazing how petrols have come on!

 

[derelyth]

Amazing how petrols have come on!

Bearing in mind that was a clear run. My commute this morning hit 38MPG (6 miles town, 30-40) though roads are dead, obviously. Normally that can be anything from 18-32...

I've seen it at 6.9 when crawling (S/S unable to kick in).

 

[gaffer1986]

I think you're right for town driving. Especially if it's a short journey. My 184 takes a good 10 motorway miles to heat up fully. As soon as you get on a run you are looking at 20mpg +

I get 65mpg on my motorway commute. Id be surprised if the 1.8tsi got 45mpg as the 2.0tsi golf I used to use was mid to high 30s.

Thing is, I'm in the unusual situation where I do loads of miles but in town. The car heating up shouldn't make much difference because I drive it round town 8-12 hours a day so the car spends most it's time up to temperature. I just find diesels only slightly more eco round town than modern petrols, I think this is because the gearing of diesels are more set up for motorway use whereas you can drive a modern petrol round town using the same revs as a diesel by utilising a higher gear which takes away the advantage that diesels rev lower. I do between 25 - 30k miles a year, mostly round town.

Sent from my HTC One S using Tapatalk

 

[DeanC]

No brainer for you. I'd say you need to be doing at least 50 mile commutes on 50mph+ roads for a derv to make sense.

A diesel is better at idle but start stop has taken away that benefit.

 

[gaffer1986]

No brainer for you. I'd say you need to be doing at least 50 mile commutes on 50mph+ roads for a derv to make sense.

A diesel is better at idle but start stop has taken away that benefit.

That's true and now all decent petrol engines are direct injection diesels have even less advantage at slow speeds.

Although the DPF has surprisingly only effected one of my lessons in nearly 4 years of owning the car, it is annoying that it changes the throttle response when it's actively regenerating as it confuses my customers, I've also noticed that there is far less engine braking during an active regen.

I can't understand why they can't make a longer 6th gear on the petrols, the 1.4 TSI has the same torque figure at the same rpm as the 1.6 TDI, so I'm sure the petrol could handle 70mph at 1800 rpm. The 1.4 TSI currently revs at 2200 rpm in 6th gear at 70 mph, I'm sure a longer 6th gear would save fuel.

Does the eco button actually make a difference to your economy?

 

[DeanC]

No it makes mine worse as I get frustrated at the lack of response and end up flooring it to activate the kickdown button when any amount of real power is needed. I find normal the best, sport is too much too soon so you don't drive smooth and eco is too little too late.

 

[gaffer1986]

Sounds like the modes are a little pointless. It should be like the M button on the M5 and M6 when you get a extra 100 BHP.

Sent from my GT-N5110 using Tapatalk 4

 

[DeanC]

That would go down nicely. And do whatever sports mode does to my uncles TT RS' exhaust note!

 

[rcopus]

Coming from Mk5 Ibiza 2.0 TDI - I find the Normal mode on my 1.4 TSI Leon makes me drive a bit more 'sensibly'.
Because putting your foot down doesn't result in instant maximum power it means my acceleration is more gradual and I'm probably driving more efficiently.

At first it was a bit hair raising though pulling onto roundabouts and expecting maximum power straight away

 

[derelyth]

I found eco downright dangerous when I used it. Once. A good second delay between throttle pressure and the clutch biting (DSG) - one wrong decision and you'd be buggered..

Sport mode is great in the right conditions. Really let's the car stretch it's legs :-D

Sent from my Nexus 4 using Tapatalk

 

[gaffer1986]

I didn't find much difference in the modes when I test drove the car, but I must admit I was playing with them on a dual carriageway cruising at 70mph where it will probably make no difference and left it in sport mode when I got to any junctions. I much preferred the steering in sport mode.

 

[Fraczish]

I like to drive in eco, only because its not as dangerous as the DSG in eco appears to be and I love the massive difference when you flick it into sport! Not sure it helps the fuel economy though because you end up using a wider throttle position to compensate...
I am taking a trip down to Cornwall on Sunday so will post my figures for a 250 mile round trip 50% motorway 50% fast moving A30, hoping for at least 45mpg

 

[gaffer1986]

I went on What Cars True MPG and compared the 2.0 TDI 184 with the 1.8 TSI.

When the driving style was set to motorway, not busy and eco driving the diesel claimed 56.1 mpg and petrol 45.5 mpg (10.6 mpg difference).

When I changed the driving style to town, busy and not eco driving the diesel claimed 36.9 mpg and the petrol got 33.8 mpg. (3.1mpg difference).

So this backs up my experience that around a busy town, the economy of diesel diminishes far more than petrol (even when both cars are up to temp). Petrol's economy seems to be less sensitive to driving conditions.

It seems that diesels gain most their economy from lower revs at higher speeds. If it gained economy due to a higher compression ratio and the fact that diesel has more energy, diesel would surely be more economical round town and the motorway.

 

[gaffer1986]

Just proved myself wrong about the diesel achieving more economy due to lower revs.

I just compared both cars driving quickly on the motorway and they were nearly the same. Diesel got 45.2 mpg and petrol got 44.2 mpg.

According to What Cars True MPG, diesels are only more economical than petrol when driven very economically at a motorway speeds. Any other driving conditions achieve similar results to the petrol.


Fifth gear should do a test to see what type of car is most economical for driving conditions. i.e. town, country roads, motorways and rush hour traffic. Would be interesting to see the results between petrol, diesel and hybrid.

If this was common knowledge, I reckon there would be less diesels on the road.