Fabia VRS MPG - How to improve?

[Pinchy]

Just wondering..

Apart from the obvious; driving carefully, Fuel aditives, wheel alignment and so on.

How do you make sure you get the best MPG out of a diesel engine? What sort of maintenance etc. would help?

[mgolder81]

No unnecessary weight. Right tyre pressures. Try not to have journeys short enough for the engine to not warm up properly as well I presume? Which is difficult, as this engine takes a while to warm up ha ha

[softscoop]

Thrash the hell out of it on occasion to make sure it's nice and clean

Check your tyre pressures are correct often.

Then, drive smoothly, anticipate junctions, use your gears and engine braking, and maintain a stead speedy rather than braking, accelerating, braking, accelerating etc.

Personally I never bother with fuel additives, I've never noticed them make any difference to MPG. Driving properly is the key to good fuel economy.

[CookieMonster]

I found that with my petrol car the lower the rpm the better. I drive around town at 1100rpm. However with the VRS it seems 1750rpm is the most economical rpm.

That means at 30mph

Petrol = 5th gear

VRS = 3rd gear

Feels wrong but try it and see.

Means i change gear more though as

Petrol 30mph - 70mph = 5th gear

VRS 30mph = 3rd gear, 40mph = 4th, 50mph = 5th etc

But this may vary between cars based on how well it is serviced, if it is moddified. If you have the earlier or later VRS engine. I believe there was a change in gear ratio as well.

Edited 8 October, 2012 by CookieMonster

[Phil-E]

Check the MAF is cleaning and working well. Check for boost leaks.

The best way to get good economy from these engines I've found is to try and get off the throttle as much as possible. Not so easy on a steady cruise but on A roads etc it's very easy to do while sticking to the speed limit.

Phil

[Skodaniel]

Mine seems fairly rubbish on fuel, driven normally on the motorway at 70-80 I can only achieve 40mpg tops! Around town etc is 31 ish. It was remapped before I had it but I don't know who or what too.

[stuart vrs]

hi there,

firstly put plenty of fuel in, brim it, then press the little button inside the tank filler pipe this makes a hissing sound and the fuel will disappear,

keep filling and keep an eye on the litres you put in, recently i put 45litres in my tank with 105miles left on computer, after i filled it, not to the brim though (thought there was a hole in my tank) i then pressed the computer button and was told 630miles in tank,

i've already done 145miles and needle hasn't moved of full and computer telling me still got 510miles left, i'm trying the shell v-power diesel, i clock up 60miles a day, motorway driving average 58-60 mpg @ 60-70mph traffic permits. hope to get a good mileage out of this tank, going to do a 3 tank fill using v-power. might be worth the extra coin for more mileage.

[vrsRob]

Yeah, my MPG is also rubbish, went to Yorkshire weekend before last, cruising at around the speed limit all the way and only got 76 MPG

After a bit of pottering around up there, trip to see friends in Lincoln then home, filled her back up and overall got just 68 MPG for that tankful :think:

[TimVRS12]

I used v-power religiously in my petrol polo, didn't make a difference to mpg.

To the poster who has problems with their mpg, check out your MAF.

I had poor mpg, an spent months complaining about it on here and trying to find the source. Soon as I changed the MAF and laid off the right foot ideas making solid returns.

[Skodaniel]

I used v-power religiously in my petrol polo, didn't make a difference to mpg.

To the poster who has problems with their mpg, check out your MAF.

I had poor mpg, an spent months complaining about it on here and trying to find the source. Soon as I changed the MAF and laid off the right foot ideas making solid returns.

I must first research this maf, once i know what it is and where i can find it ill look into it, cheers

[BlueRobin]

Cruise in neutral down hills, but make sure you keep your speed up and consistent. Got 10% extra when commuting through the Cotswolds.

[TimVRS12]

Mass Airflow Sensor.

Measures air flow into your engine. It's the sensor that found after your air box, a wire plugs into it.

Replacements are best bought from ECP using Brisky's 25% discount plus the rebate for an exchange, works out at around £65 for the replacement after both

[Titanium_Man]

Cruise in neutral down hills, but make sure you keep your speed up and consistent. Got 10% extra when commuting through the Cotswolds.

Wanna keep it in gear, uses more fuel coasting I believe

[Skodaniel]

Cheers Tim. Can it be checked?or just a 'replace and see if it makes a difference' job?

[TimVRS12]

If your is knackered, supposedly if you remove it, it shouldn't alter how the car behaves.

I did this and my car felt terrible, lost power. So this doesn't always apply.

Without getting it on rollers, I don't think there is a solid way of testing without borrowing someone else's functioning one and tryin it out.

[cheshire_cat]

20K max on the air filter and a clean EGR valve

[gac]

Cruise in neutral down hills, but make sure you keep your speed up and consistent. Got 10% extra when commuting through the Cotswolds.

Wanna keep it in gear, uses more fuel coasting I believe

Indeed, coasting in gear will stop fuel from being injected at all on modern engines because the roles are reversed and the gearbox keeps the crankshaft turning (rather than vice versa). If you're coasting in neutral then you're injecting fuel simply to keep the engine at tickover; not a massive amount admittedly, but it's more than "none".

Cheers Tim. Can it be checked?or just a 'replace and see if it makes a difference' job?

You can log expected airflow vs actual airflow with VCDS. It won't 100% disprove a slowly dying MAF, but as long as it's able to make the readings it needs to then it's "good enough".

[BlueRobin]

Forgot to say decay speed in neutral approaching a slower speed zone, but you'll need to anticipate. Your theory doesn't bear up against my stats when I used to do this.

Always drive in warm summer air is another one ;-)

[TeebsVRS]

I found that with my petrol car the lower the rpm the better. I drive around town at 1100rpm. However with the VRS it seems 1750rpm is the most economical rpm.

That means at 30mph

Petrol = 5th gear

VRS = 3rd gear

Feels wrong but try it and see.

Means i change gear more though as

Petrol 30mph - 70mph = 5th gear

VRS 30mph = 3rd gear, 40mph = 4th, 50mph = 5th etc

But this may vary between cars based on how well it is serviced, if it is moddified. If you have the earlier or later VRS engine. I believe there was a change in gear ratio as well.

Definitely this.10mph per gear definitely feels the sweet spot, despite all the green and govt rubbish about lowest revs possible. Labouring an engine is not good for it,or MPG.

Improving MPG is definitely all in changing your driving style, once the basics like tyre pressure and excess weight are sorted.

[andypandypoos]

Yeah, my MPG is also rubbish, went to Yorkshire weekend before last, cruising at around the speed limit all the way and only got 76 MPG

After a bit of pottering around up there, trip to see friends in Lincoln then home, filled her back up and overall got just 68 MPG for that tankful :think:

680 miles from 45l is pretty damn good, I've managed 50mpg over a tank but I'm pretty sure my Ibiza wouldn't get that no matter how hard I tried :|

[Oli3000]

Yeah, my MPG is also rubbish, went to Yorkshire weekend before last, cruising at around the speed limit all the way and only got 76 MPG

After a bit of pottering around up there, trip to see friends in Lincoln then home, filled her back up and overall got just 68 MPG for that tankful :think:

You must be doing something mental. I can get 550 out of 39 litres (never take her totally to empty), so 600 out of 45 in my PD100 when doing 60-70 on the motorway - you must be REALLY cruising along! That or you have some sort of ingenious remap!

If I did 600 miles on A roads at 50-60 I could probably manage 80s and upwards, but above 60mph, 65 mpg is about the best I can get!

Also, NEVER do anything in neutral. Also use engine braking to stop or roll down hill in gear as there is zero fuel going in. It's not worth all the rolling for the extra few mph you'll gain in the long run! Avoid braking and predict the road ahead - if you are gaining on the car in front of you back off the throttle early, and pick speed up again when they move. Don't drive up behind them and break. Again, same goes for roundabouts, try and predict when there is going to be a gap, or if there is a queue get off the throttle a long way off - it doesn't lose you any time, you'd only spend it queueing anyway!

[Phil-E]

680 miles from 45l is pretty damn good, I've managed 50mpg over a tank but I'm pretty sure my Ibiza wouldn't get that no matter how hard I tried :|

I find these engines are very easy to get good MPG.

We recently drove from York to Kent to Folkestone to Germany with 1/4 tank still left and that's 2 adults, 2 folding bikes and a boot full to the brim of camping gear (our boot is 485 litres).

Phil

[BlueRobin]

If there is zero fuel, why does the engine keep combusting?

[Phil-E]

If there is zero fuel, why does the engine keep combusting?

It doesn't. It is just forced to turn by the gearbox etc but there is no fuel being injected.

That's why the MPG display goes to "- - -" when you lift off the throttle and the trip MPG goes up really quickly.

Phil

[Oli3000]

It doesn't. The engine is pushed round by the wheels.

Rolling in gear:

Wheels turn the gearbox -> gearbox turns the driveshaft -> pistons go up and down -> ecu adds no fuel.

Rolling in neutral:

Fuel goes in -> explodes -> pushes pistons -> drive shaft rotates -> no connection to gearbox -> energy lost. Wheels roll and spin gearbox with no connection to anything -> energy lost.