This discussion is now closed.

Check out other Related discussions

how to get more mpg from my diesel?

hi guys,
i've just been reading some reviews for my car and i've seen people say they get anything between 450 and 600 miles from a full tank.
i generally get 350-400. i'm new to diesels having previously driven a petrol car (this is my second car) so i was just wondering if anyone in the know could tell me when i should really be changing my gears up and down rev-wise?
i generally drive on 40's, 50's and 70's round here so i would have thought i should be getting better much better mpg then what's stated as urban mpg

responses would be much appreciated :smile:

btw its a 1.8 tdci focus

Reply 1

Mattgeezer

1

try and keep revs below 2k, and as high a gear as possible, also plan ahead, no hard acceleration, no hard breaking.
Do you have a sixth gear? and a trip computer to show average mpg?

Reply 2

Mattgeezer

1

Also with your calculations it seems like your only getting around 28 to the gallon, somthing is seriously wrong...

Reply 3

cameronmcgarry

1

Mattgeezer

Also with your calculations it seems like your only getting around 28 to the gallon, somthing is seriously wrong...

yeh thats mental, keep the revs down that'll be the major difference between diesels and petrols, but also on the acceleration just keep your foot more smooth and slow than you would have on your petrol, oil burners hate being raced off the line but they're good cruising at 70+

Reply 4

Steeps

11

The key is how long your journey is. My work run is on 40/60/70 but it's only getting me 400 miles out of my tank with it 8 miles each way. When doing Bradford to Canterbury I can get there and back on a full tank. Most impressive statistic was going though some SPECS and it reckoned I could do 750 miles more at that speed.

Diesels have more torque compared to the equivalent petrol engine so somewhere near 2k is generous for a gearchange, still it's best to avoid doing short trips if possible as these are the ones that drink the most, engine warming up etc.

Reply 5

div curl F = 0

9

Don't have the fans on, don't have AC on, don't use the rear window demister, keep the windows up, don't drive around with headlights on when not needed, don't sit with your foot on the brake pedal when stationary (i.e. put handbrake on). All of these make the engine work harder than necessary, either by putting direct strain on the engine (like alternator, AC pump) or on the aerodynamics of the car. Some of these are minimal effects but when added together they can become noticeable.

Reply 6

CurlyBen

19

Make sure you don't just plant your foot when accelerating, you need to give the turbo some time to spool up. I don't know if it's improved in the common rail engines but in older diesels you could end up wasting a lot of fuel as there wasn't sufficient air getting into the cylinder if the pedal was planted but the turbo wasn't operating effectively.

Reply 7

Cj-Tj

15

Mattgeezer

Also with your calculations it seems like your only getting around 28 to the gallon, somthing is seriously wrong...

How do you work that out? 55 litre tank, 350 miles. Say a "full tank" is 48 litres when you get to the filling station, I make it 33mpg. If you take the higher value of 400 miles to a tank then you get 38mpg.

Those diesels should do about 40-45, but if people think they are getting 600 miles thats 56mpg. Will be achieveable on motorway runs, but for normal use if your getting 45 your doing well. My 1.6 petrol focus is currently returning about 25-28mpg.

Reply 8

RightSaidJames

16

I regularly get 53+ mpg and on the right route that can go as high as 58 or even 60. I concur with what everyone else says - change up a gear when you get to the 2100-2200 revs mark and resist changing down until you feel that it is necessary. Diesel cars don't need such high revs as a petrol to maintain a decent acceleration; if you change up a gear and end up at 1200 the car will still be able to recover, but if you start off at 1400 you won't really have any problems. When you're at a constant(-ish) speed, change to a gear that gives you less than 2000 revs, you don't need any more than that.

Reply 9

Tofufi

4

Cj-Tj

My 1.6 petrol focus is currently returning about 25-28mpg.

That's awful! my 40 year old 1.6 litre van, which is woefully underpowered (50bhp originally) can manage that sort of MPG, up to 30 on a gentle run :smile:

40 years of progress and no increase in MPG? I'd imagine your focus gets driven harder then!

Reply 10

aqfrenzy

OP

2

will the fact i'm running an aftermarket head unit and about 650w rms / 2000w peak worth of amplifier make much difference to my fuel consumption?
what is the lowest rpm you can run at in a gear and try to accelerate from without damaging the engine

i think the main reason my consumption is so high is that when accelerating i always go past the 3krpm mark and im very heavy footed. when im going at a steady speed i try to go in as high a gear as i can but im never sure if im ruining the engine or not with such low revs on the gear because when i used to drive a petrol too high a gear the engine starts shuddering and my dad starts shouting 'ur gona kill the f**king gearbox' lol

Reply 11

aqfrenzy

OP

2

Mattgeezer

try and keep revs below 2k, and as high a gear as possible, also plan ahead, no hard acceleration, no hard breaking.
Do you have a sixth gear? and a trip computer to show average mpg?

no sixth gear, no trip computer... wish i had one, would have been useful!

Reply 12

tomc87

1

aqfrenzy

what is the lowest rpm you can run at in a gear and try to accelerate from without damaging the engine

Depends on loads of things eg. gradient of the road, number of people in the car etc.

There isn't a specific figure, but if the engine feels like it's labouring then you should be in a higher gear.

Reply 13

tomc87

1

Cj-Tj

My 1.6 petrol focus is currently returning about 25-28mpg.

This concerns me as I was looking at a 1.8/2.0 Focus as one option for my new car in a few weeks, but if mpg is that bad on the 1.6 maybe I should be reconsidering!

Reply 14

aqfrenzy

OP

2

tomc87

This concerns me as I was looking at a 1.8/2.0 Focus as one option for my new car in a few weeks, but if mpg is that bad on the 1.6 maybe I should be reconsidering!

go diesel

Reply 15

Minardi

12

I can acheive 33mpg in a 2.5 TD5 Defender on a run.

You shoud change up at about 2k, max, and run the car at practically idle in 30's and 40's. The landie crusies at 27 in 5th at idle, which is great for 30's, uses next to no fuel. You should be able to happily cruise about at steady speed down to about 1200 revs. Diesels have a far greater reserve of low down torque to enable that.

Reply 16

Cj-Tj

15

tomc87

This concerns me as I was looking at a 1.8/2.0 Focus as one option for my new car in a few weeks, but if mpg is that bad on the 1.6 maybe I should be reconsidering!

Nah, its how its been used for the last few tanks, lots of very short (sub 5) mile journies, and when used on journies longer than that has generally been hammered. Plus it needs a service which it will get over Chirstmas, that should sort it back out. Motorways will get about 42mpg if im nice, and normal driving can expect about 32-35, again, if im nice.