Fuel economy - 1.5dCi

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Fuel economy - 1.5dCi

Postby SirSerf » Sun Jan 14, 2018 2:29 am

Update # 2. Still looking for something more significant in my search for mpg! I've started looking at diesel additives and wonder if there is any experience out there on what ones work and what ones are 'snake oil'.
When I popped into my local Halfords I was confronted with a wall of options!


The one comfort I suppose is that with so many fuel additives on offer it must be a good market and plenty of car owners are adding these to their fuel. The concept of cleaning up your fuel combustion system does kinda make sense, diesel isn't the cleanest of automotive fuels and over time some deposits must build up. These deposits over time must surely account for the deterioration in mpg from the 'new' figures'? So if you can clean the injectors and cylinders to 'as new' then maybe I'll get 'as new' mpg!!

The one thing that puts me off using any fuel additive is wondering why the the fuel companies are just doing it anyway. I do recall that back in the last Millennium one of the fuel companies, Texaco I think made a big launch of the new super cleaning fuel only to withdraw it from sale within the year as it apparently went too far is it's cleaning and destroyed a few engines!!

Any advice appreciated.

Update - one week later! So after one week and 500 miles of driving on tyres with the correct air pressure did it improve my fuel economy? Yes! On my long daily commutes I achieved approx. 2 mpg better! I was getting around 54-55 mpg but after checking and inflating tyres to correct psi I am getting around 56-57 pg mpg on the same commute. Not dramatic but the saving will more than pay for the cost of the gauge and go a good bit towards a routine service!

Why don't I get the high mpg claimed by Renault for my 1.5dCi 110 bhp Mégane! One of the driving factors in my choice of my 2013 1.5dCi was the great fuel economy figures cited of 68-80 mpg. However I'm not seeing near this in my driving. On a motorway run, which is most of my driving I get 53-55 mpg, around town at best it's 50 mpg. Not bad in comparison to some cars but still not near the manufacturers claims from new.
I would like to know what the more experienced Mégane owners on this forum would recommend to get my mpg higher!

One of the first things I went about checking was tyre pressure. I had read in the past that under inflated tyres create more drag with the road which is paid for in higher fuel consumption. From what I read even a couple of PSI on the low side could make a noticeable difference so relying on a service station air pressure gauge might not give me the accuracy I needed. From experience of garages in my neck of the woods I have seldom found a good clear gauge on those hand held air pressure lines that can be easily read. I decided I needed a reasonably accurate easy to read gauge of my own. After a bit of research on-line I settled on this TireTek model. This gauge is is calibrated to ± 1 psi at 30 psi.

https://tire-tek.com/collections/all-pr ... cle-60-psi

The good thing I found with this gauge is the hold feature that lets you remove it from the tyre valve and the dial stays at the pressure until you release it with the button.


Visually checking if your tyres need inflating is hopelessly inaccurate and really the only way of knowing your tyre is correctly inflated is to stick a pressure gauge on it. This was my first shock! The car is a recent purchase and was serviced and checked before I picked up. The tyres looked fine to the eye but when I checked them with the gauge they were between 6-8 psi lower than recommended!


So I went to my local garage (with new gauge in boot!) and inflated my tyres to 35 psi front and 33 psi rear. I haven't any long runs yet to see any difference in mpg but will update!
In the meantime I'd would be interested in hearing what else I could do to improve mpg?

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2014 Mercedes ML

Re: Fuel economy - 1.5dCi

Postby crosser74 » Thu Apr 26, 2018 7:03 am

I think your achieved figures are about as good as it will get in my experience with the same engine.

Don't forget, published figures are best used a comparison between cars as they are usually impossible to achieve in the real world. Parts are removed from the cars to shed weight, body panel gaps sealed to reduce drag, simulated perfect conditions etc. etc. :?

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Re: Fuel economy - 1.5dCi

Postby steve-t » Thu Apr 26, 2018 3:03 pm

Have you thought of a Terraclean?

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Re: Fuel economy - 1.5dCi

Postby Chrali » Fri May 11, 2018 11:49 pm

My driving is in Norfolk so no steep hills and mostly dual carriageway and the worst I've got in 30,000 miles of driving is 50.95 mpg and the best is 65.2 mpg; although that tank was driven gently to see how high I could get mpg.

Summer driving usually averages out at 62 mpg, with winter at about 55 mpg. I believe in regularly revving a diesel out, and don't baby it. Mines currently at over 76,000. I too was hoping for high 60s+mpg, but that's never going to happen as the govt figures would include the benefits of the stop/start in urban driving, whereas my driving rarely invokes the stop/start.

I wouldn't waste money on aftermarket fuel treatments, just running decent fuels should keep everything clean enough. I always use BP, perhaps start of with a few tanks of BP ultimate, or whatever fuel that contains extra cleaners that takes your fancy.

Encourage alternative fuels, use all the petrol and diesel!

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