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Diesel fuel economy, realistic, poor or just me?

987 Views 19 Replies 9 Participants Last post by  BossHogg
Hi all, happy to report I'm back in a civic (mk10), bought a 2018 1.6 diesel with 40k on the clock (2018 plate). This is after having a mk9 with the same engine (2014 plate) all be it with a gap (went 'posh' and had a v90 for 18 months, spoiler alert, the honda is more reliable), both effectively same engine, same manual box etc.

Anyway, I do faily mega milage (30k a year at least) and I'm 10k in from when I bought the car in late December. When I bought it almost immediately I had an issue with an engine light which ended up being 1st lambda sensor (replaced by honda). Prior to the 'fix' I was really struggling to hit 50mpg but put this down to being understandable. Since the fix the mpg has improved, however I'm struggling to get more than high 50s. I've got it into low 60s on a proper eco drive of say 30 mile or so, but never getting anywhere past mid 60s, but really REALLY trying.

I should point out that my driving (by nature of the miles I do) is mainly national speed limit roads cruising at 60 the majority of the time, and motorways sitting in the mid 70s of cruise. I have tried not using cruise, tried turning eco off, and back on for good distances and with basically zero effect.

I drive the same roads as I did in the mk9 and regularly was hitting 70mpg, often mids and over long distances.

Is this normal? I appreciate it may be a bit worse than the mk9 with weight etc but didn't expect such a big difference (I would say 15mgp average worse). My concern is that there's another fault or issue that caused the lambda to fail that's still in the background. Car drives fine etc. Could this be where someone has put petrol in it or something?? And comments/suggestion etc much welcomed ta
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Last properly calculated MPG I did on mine I got was 58mpg, that's mainly from a 13 mile commute. I do expect this to rise now that the cold weather is past. TBH Im happy with this, but I came from a petrol Gen8 so that's understandable, but yes its way short of Hondas official figures which is around about 80mpg.
Can’t give advice specific to the 1.6 i-DTEC engine, but I’m now averaging 50mpg out of a 1.8 i-VTEC petrol:

Check the wheel alignment - this can make a big difference if the front tyres are scrubbing. The Mk10 has independent rear suspension so have a 4 wheel alignment check done.

Check the tyre pressures.
Perhaps change the tyres to an ‘Eco’ variant from a premium brand.

Service the brakes. Make sure all calipers and pads are correctly lubricated and not binding.

Try running super diesel (V-Power etc.) if not already.

Goes without saying: keep your speed down. Don’t drive over 70mph on motorways (air resistance starts to have a large effect), and generally just keep to the speed limit.
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With these sorts of mpg its difficult to justify electric cars.
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The 9G is pretty aerodynamic and I think that's what makes the difference between them having 'good' and 'excellent' fuel economy.

Real MPG figures for the 10G suggests that it averages quite a bit less than the 9G. But then it's a bigger, heavier car with a slightly less mad side profile so it makes sense.
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Managed to get the BC up to 78mpg over 76 miles today. The fuel gauge hasnt moved at all.
Shame the weather is too be pants for the return journey tomorrow.
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We have a MK9 and a MK10.
The MK10 always does less miles to the gallon than the MK9. There was mention that the MK10 uses a it more fuel for The DPF/ emissions when we bought it.
We have a MK9 and a MK10.
The MK10 always does less miles to the gallon than the MK9. There was mention that the MK10 uses a it more fuel for The DPF/ emissions when we bought it.
Out of interest what difference you seeing? As mentioned I think I'm a good 10-15mpg different from my old mk9. I'm planning a good service and possibly even bluespark to see if it improves things. I do big miles so any improvement will save me money in the longer term. Just a bit disappointed with the mpg I'm getting vs what I kinda expected
Can’t give advice specific to the 1.6 i-DTEC engine, but I’m now averaging 50mpg out of a 1.8 i-VTEC petrol:

Check the wheel alignment - this can make a big difference if the front tyres are scrubbing. The Mk10 has independent rear suspension so have a 4 wheel alignment check done.

Check the tyre pressures.
Perhaps change the tyres to an ‘Eco’ variant from a premium brand.

Service the brakes. Make sure all calipers and pads are correctly lubricated and not binding.

Try running super diesel (V-Power etc.) if not already.

Goes without saying: keep your speed down. Don’t drive over 70mph on motorways (air resistance starts to have a large effect), and generally just keep to the speed limit.
Thanks for this. It has actually had 4 wheel alignment done and tracks well, so I'm presuming at least it's good. Do check pressures etc. It's more my real world mk9 to mk10 I'm about 10-15mpg worse off in same conditions. Just a bit worse than expected. Normally expect better, even if it was close I would be happy, just not brilliant
Out of interest what difference you seeing? As mentioned I think I'm a good 10-15mpg different from my old mk9. I'm planning a good service and possibly even bluespark to see if it improves things. I do big miles so any improvement will save me money in the longer term. Just a bit disappointed with the mpg I'm getting vs what I kinda expected
Just below 60mpg and just below 55mpg.
As I understand it a bluespark might show an improvement on the trip computer but in reality as it lies to the ecu and tells it the boost is slightly lower than it actually is and extends the injection time the only way to tell if it’s doing any good is to calculate mpg by the top the tank method.
Not saying there isn’t any fuel savings to be had with one just something to consider.
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do you check tank to tank or just use the display? My 9g is up to 10% optimistic. So if just using the display the newer one could just be more accurate
I do tank to tank and then do the sums. We usually let them run down to the last 100 miles or so and then fill up to the top. Hate going to the filling station. Just been to check and the 10g mpgometer does appear more accurate.
Just broke the 600 mile range barrier for the first time today, 70 mpg avg over 160 ish miles. And Diesel down to £144.9 at Morrison's here now too.
It's down to 141 for diesel where I live. 👍
About time. Wholesale diesel is 9p/lt cheaper than petrol, pure profiteering from the fuel stations now.
It's down to 141 for diesel where I live. 👍
are you the 1 on forum from maryport ?
whos selling derv for 141 ??
About time. Wholesale diesel is 9p/lt cheaper than petrol, pure profiteering from the fuel stations now.
it was 14p cheaper a week or 2 back
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are you the 1 on forum from maryport ?
whos selling derv for 141 ??
I am Marra. 😁 I fill up at Tesco and Asda in Carlisle. It's also 1.45 in the spar garage in Maryport and 1.44 Asda Workington. I have a Blue light card which gives me Esso discount so I pay 141 at Aspatria petrol station.
I have a Blue light card which gives me Esso discount
O rly? TBH I dont think there are any Esso in my area, many in Scotland full stop but nice to know.
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