Purchased a nice little 500L in September for my wife, car is great but the fuel economy has gradually got worse (from at 42mpg so not great anyway) and according to the trip computer is currently about 35-36 mpg which seems incredibly low.

I’ve checked things like tyre pressures but no idea what to look at next. Any ideas?

Welcome at FiatForum.

When was the car last serviced..?

Thanks. It’s a 14 plate car, 50k full main dealer service history - last serviced end February last year

Well than it's due for a new service soon, once a year, remember..
Have it done, and see if mpg improves.
( I bet it will)

Yes I’m planning on getting it serviced when due but it’s only done 3.5k miles since last service.

It’s going to fiat next week for a recall issue so I’ll get it booked in then

Come back here with results if you will!

With so few miles I doubt the service will help the fuel economy.
However, diesels like to be driven regularly and long, which probably doesn't happen often and causes a lot of things to clog up.

First thing to try is giving it an "Italian tune-up":
- with a 1/3-1/2 tank of diesel put a double dose of diesel injector cleaner in the tank,
- go for a long (2hr) drive, start driving normally,
- after about 20 minutes (engine should be fully warm by then) drive it like you stole it: pull full-throttle all the way through the rpm range in 2nd and 3rd.
- If my suspicion is right, you'll see it puffing black smoke out of the exhaust when you're giving it the beans, so do this a few times during this long trip.
- fill up the tank and reset the trip computer so you get a reference to calculate future mpg and the cleaner can further do its job slowly over a longer time during the next tank of fuel.

I'm pretty sure the mpg will go back up again after doing this.

A double dosis injector cleaner can harm the sensitive injection system, it even may cause leaks in the high pressure pump, if it contains not enough lubricating habits, so think twice before using it that way.
Stay on the safe side, and use ANY additive according to the instructions on the bottle...
Using a premium diesel fuel like Shell V-Power, or BP Ultimate will give better results, without having to use any additive at all....

Everybody is free to do what they feel comfortable with ofcourse, but keep in mind:
- diesel lubricates, you'd need to add a lot of non-lubricating fluid (much more than a double dose of additive) to 1/3-1/2 tank of diesel to reduce this to dangerous levels.
- We're talking about commercially available additive
- Premium fuel is a very good idea to keep the system as clean as possible and will clean existing contamination a bit, but the amount of detergents in premium fuel is far from what's effective to get rid of a year's worth of short-distance trips build-up quickly.

In next month's Practical Mechanics.......there will be an item about how to use fuel additives, I'm assuming they will cover most of the myths around the stuff.....and give us the FACTS from the people who know...??
Ian

In our 1.3 multijet mpw (dual-logic), we also had really poor mpg since December.

We used to get around 380 (min) to 440 miles per tank but its been decreasing to 320 then 300 and now 290. We do the usual weekend family trip around town and weekday work to home trips.

I believe its the colder than usual weather combined with winter grade diesel. It takes up more fuel to warm up the car I guess as air temperatures are pretty low in the morning when I start it for work. Traffic has increased a lot during this season due to road paving and more people using their cars in this cold weather.

I think in the summer it should return back to normal, well hopefully

The first Fiat 500L 1.6 Multijet diesel I owned, an Easy model used to average between 48 - 52 mpg in regular use. On a longer journey 60mpg was possible.

In December 2016 I changed for a Lounge, again 1.6 diesel but with the increased bhp to 120.
Whether it's the extra bhp, more options and more weight the average is around 46 mpg and you have to drive it really gently to see 52-54 mpg.

Even on long journeys I haven't seen anything near 60 mpg, 57 mpg was the best it's achieved.

EliG said:

The first Fiat 500L 1.6 Multijet diesel I owned, an Easy model used to average between 48 - 52 mpg in regular use. On a longer journey 60mpg was possible.

In December 2016 I changed for a Lounge, again 1.6 diesel but with the increased bhp to 120.
Whether it's the extra bhp, more options and more weight the average is around 46 mpg and you have to drive it really gently to see 52-54 mpg.

Even on long journeys I haven't seen anything near 60 mpg, 57 mpg was the best it's achieved.

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52/54 sounds pretty good to me!! I’m getting 47mpg

SGin said:

52/54 sounds pretty good to me!! I’m getting 47mpg

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Just for comparison's sake, we've got the 1.3 500L MPW.

We used to do around 50 to 60 mpg on the motorway, and 45ish in town. Since the start of this year it's been hitting to 34mpg in town

Same urban work routes as well Warranty ended like a couple of weeks ago (passed mot, so no excessive emissions I see no smoke at all).

Thought it was just the winter season with the snow but it's still not doing the same amount as it used to

Using Manual instead of the eco-auto does give a very slight increase of a couple of mpg.

LordMetro said:

Just for comparison's sake, we've got the 1.3 500L MPW.



We used to do around 50 to 60 mpg on the motorway, and 45ish in town. Since the start of this year it's been hitting to 34mpg in town



Same urban work routes as well Warranty ended like a couple of weeks ago (passed mot, so no excessive emissions I see no smoke at all).



Thought it was just the winter season with the snow but it's still not doing the same amount as it used to



Using Manual instead of the eco-auto does give a very slight increase of a couple of mpg.

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Tyre pressure, fuel filter , oil, air filter usually sorts it out . You would be amazed how these things can affect mpg
And plugs if you’ve got them.

I'm interested in this also. Had ours 1.6 120 3 months now and averaging 38mpg (mainly stop start traffic I admit, but some good runs). But even on a run its doing only high 40's. Fiat are telling me this is normal. Its far worse than my automatic 2ltr diesel skoda superb and not much better than the 2ltr petrol mazda5 it replaced (to get better mpg).

It has recently been serviced and all tyre pressures are fine.

I’ve got a grande punto with the same engine I get 45 combined easily and 60 on a run. Mine does lots of short journeys and runs on Asda diesel, it gets serviced religiously and maintained with multiscan ecu, all emissions equipment is original and I don’t notice a difference in winter/summer. However if you drive it in a spirited manner all those figures disappear, and probably are similar to above

Moimo said:

I’ve got a grande punto with the same engine I get 45 combined easily and 60 on a run. Mine does lots of short journeys and runs on Asda diesel, it gets serviced religiously and maintained with multiscan ecu, all emissions equipment is original and I don’t notice a difference in winter/summer. However if you drive it in a spirited manner all those figures disappear, and probably are similar to above

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when you say maintained with multiscan ecu, what exactly do you mean? Just in terms of checking for codes etc? Or can it force dpf regens etc?

Certainly checking for codes etc, but more importantly oil degradation counter reset, on its annual oil change. Mine has the dpf, one hole restrictor on the egr, and all emissions systems as the factory intended. Very Occasionally the dpf clogged message comes up and I clear it with a run, never had to do a forced regen thankfully.

Moimo said:

Certainly checking for codes etc, but more importantly oil degradation counter reset, on its annual oil change. Mine has the dpf, one hole restrictor on the egr, and all emissions systems as the factory intended. Very Occasionally the dpf clogged message comes up and I clear it with a run, never had to do a forced regen thankfully.

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OK, thank you