Do small engines really save fuel in the real world?

Leonard Hofstadter

That's the question I find myself asking after the car I had the pleasure of driving this weekend.

I've just done about 450 miles in a Mazda 3 Skyactiv-G.

Now, as those of you familiar with modern cars know, engines are getting smaller and losing cylinders to boot.

This seems to work very well in the official EU tests - we're told that you can get 66 mpg from your 1.0 litre Fiesta Ecoboost, and the latest Astra has 1.0 litre three cylinder turbo that does about the same mpg (in theory).

Those of you familiar with modern cars also know that Mazda likes to do things its own way, Mazda still uses large capacity petrol engines with no turbocharger.

Appropriately enough the car I was driving had a "massive" 2.0 litre engine (but despite this seemingly large capacity, only has 118 bhp). Now if you believed the average person, such a 'large' engine in a 'small' car like a Mazda 3 would mean you'd need to own your oil reserve. Sure 'large' engines guzzle fuel don't you know? Sure until we changed to diesel cars from the class above usually had 1.6 non-turbo petrol engines and cars in the Mazda 3 class had a 1.4 non-turbo petrol engine. I guess if we were still taxing cars on engine size this would have changed to 1.0 litre three cylinder turbos in the Mazda 3 class and 1.4 turbos in the class above.

And, the EU tests would certainly back up our small engined mentality, ever since CO2 became a big thing the manufacturers have been up to all sorts of tricks to try and eek out every last mile to the gallon, hence why we now see rivals to the Mazda 3 available with 1.0 litre three cylinder engines.

Of course, as I've mentioned before here and here, I have never managed to come even close to the super duper on paper figures that the manufacturers quote in modern cars. I know they're diesels, but the manufacturers use a lot of the same trickery with petrols to eek out those extra mpgs.

Now my driving style is certainly not in any way biased towards economy, but I was always able to come very close to the combined mpg figure in cars from 10-15 years ago.

This neatly brings me back to the Mazda 3 with its 'large' and 'gas-guzzling' 2.0 litre engine. I was led to believe from the What Car True MPG tests that in the real world, these Skyactiv petrols are surprisingly good on fuel economy, far better than the stereotype for such relatively large engined petrols would have you believe.

On Saturday I drove about 330 miles, which was about 95% motorway/dual carraigeway driving (mostly at about 130 km/h, but some 80 km/h runs due to roadworks) and the other 5% was urban driving. I then filled up yesterday morning (Sunday) to work out my fuel consumption. I was pleasantly surprised by the fact that I managed 42 mpg! For what it's worth, I drove a Mondeo 2.0 TDCi last year on the same journey as I did on Saturday, and got 45 mpg - just 3 mpg more, and at the time I was quite impressed with the Mondeo's fuel consumption bearing in mind the speeds I was travelling at. Now I know the Mondeo is a much bigger, and heavier, car but still here is a (relatively) large capacity petrol engine giving a diesel a run for its money on fuel consumption!

Then yesterday (Sunday) I drove about 65 miles, which was about 60% city/urban driving at 50 km/h or less, and the rest was suburban/rural driving, at up to 100 km/h (but most of it was closer to 80). As you'd expect, this proved to be a more frugal enterprise, but even so I was astonished when I re-filled the tank to find I'd gotten 47 mpg:eek:! This was all the more impressive as the trip computer indicated I'd 'only' managed about 43 mpg.

The first thing that struck me is that in the real world, this 'Skyactiv' technology works bloody well - for petrol engines at least. The other thing that struck me is that while again the Mazda did not meet its official mpg, it's come a damn sight closer to it than the other cars I've driven recently. It's supposed to do 55 mpg, and I came reasonably close to it on Sunday, and on Saturday for a petrol engined car to do over 40 mpg when the majority of the driving was at nearly 130 km/h is very impressive indeed.

I've driven a variety of NA petrols from 1.4 to 1.8, from as small as Corsas, to as big as Avensis/Mondeo, and I've never managed such good mpg. I've topped 40 mpg in petrols before, but at considerably slower speeds.

I must also say that the rest of the car itself is excellent, apart from the interior plastics, which are typical Jap car hit and miss. There's a lot of cheap materials, and I didn't like the clutch either (the biting point is extremely sharp on it), but the handling is very composed, the engine despite being rather slow for a 2.0 has a good bit of pull low down for a NA petrol and even though the gearing is ridiculous for a 118 bhp petrol (in sixth it's only running at about 2400 rpm at 130 km/h:eek: - I'm used to similar powered NA petrols running at around 3500 rpm at similar speeds) it actually has enough go most of the time and only on steeper hills does it need a downshift to maintain speed. Also worth noting is that the last time I drove a direct injection petrol was a Mitsubishi GDI, and my goodness things have moved on so much from then, granted the Mazda's engine note wasn't the most appealing (and not in keeping with the 'zoom zoom zoom' tagline) but it's every bit as smooth and responsive as the best four cylinder NA petrols are, and it's willing to be revved hard as well (although it's so long geared and fast enough most of the time there isn't much need to do this in reality).

I have to say, it's a terrible shame this engine isn't available in the Irish market Mazda 3s (to the best of my knowledge), because it's fast enough for the majority of people, it handles well, it's comfortable (the seats are very good), and because it runs at such low revs you can't hear the engine at higher speeds (unlike most smaller capacity NA petrols where you always hear four cylinder drone in the background at motorway speeds). It's a really great car (I'd have it over the Auris and Octavia I've driven over the past few months), and I don't understand why it hasn't got better reviews to be honest. I hope people will take a look at it if they're in the market for a family hatchback - were I in the market for one I'd gladly part with my cash for it. And because it's a NA petrol, there's no DMF, or turbo, and hopefully nothing else expensive to go wrong either. The only concern I have from a reliability perspective is the reputation the Skyactive diesels are getting - they seem to suffer from the same design flaw that blights the older MZ-CD in-house Mazda diesel. I just hope this Skyactiv petrol will be like the Mazdas of old for long term reliability.

Anyway, I'd be curious to see what the rest of you think? I haven't driven a 1.0 litre three cylinder turbo yet (aside from the claimed fuel consumption, I'm really keen to see what they're like to drive because I've heard such good things about Ford's 1.0 Ecoboost in particular), but I'd bet in the real world the 2.0 non-turbo four cylinder Mazda does better mpg. I'm not suggesting of course that we all go out and by V8 petrols of course, but I am very sceptical about this recent rush to offer engines that were traditionally considered to be far too small for certain classes of car. I know I've certainly never managed such good fuel consumption in a petrol engined car before - and I certainly wasn't trying to get the best possible mpg while I had this car either. Also worth pointing out that I did the same journey (and at similar speeds) as I did on Saturday in a 1.4 NA Corsa at the start of the year, and only managed 40 mpg, yet in the larger-engined, heavier Mazda I got 42 mpg!

166man

Jeepers that's some essay of a post..:D



In my own experience I recently had two rental cars. One was a Mondeo 2.0T Ecoboost engine and the other was a Dodge Charger 3.6 V6.

Without a shadow of a doubt the Dodge was better on fuel. I did plenty of miles in both and tended to drive them on a bit (:D) but even still the Dodge was rarely stressed on the motorway.

In town they were about the same - pure sh1t..!

dr.fuzzenstein

Those engines will deliver those figures...in a lab. You would have to keep off the boost at all times and even then you wouldn't get near it.
I'm just waiting for the petrol scandal to break when "suddenly" people are "shocked" to find out the MPG is horsesh*t and the emissions figures are complete fantasy.

jimgoose

dr.fuzzenstein wrote: »

Those engines will deliver those figures...in a lab. You would have to keep off the boost at all times and even then you wouldn't get near it.
I'm just waiting for the petrol scandal to break when "suddenly" people are "shocked" to find out the MPG is horsesh*t and the emissions figures are complete fantasy.

I had a NA 1-litre back in the late '90s that routinely returned around 22MPG.

Sh1tbag OToole

jimgoose wrote: »

I had a NA 1-litre back in the late '90s that routinely returned around 22MPG.

Needle probably never saw the left half of the tacho while the engine was running

jimgoose

Sh1tbag OToole wrote: »

Needle probably never saw the left half of the tacho while the engine was running

Needle spent a lot of time yowling towards 11,000 RPM. :pac:

Foxhole Norman

My 525i Auto is more economical than my 520i Manual, the extra torque and power really makes a difference.

duffman3833

you would think that the smaller engines would use more fuel on long journeys than a big 2.0l petrol engine as it would be revving higher than the bigger engines. I remember my 1.0l corsa back in the day and it was screaming past 4k on motorway trips. Upgraded to a corolla 1.4 and it was just over 3k revs if i remember. I never driven a big engine petrol car (i have driven them but never owned one to see what its like on daily basis) but it would sit at a lower RPM on longer trips on B roads and motorways so it should use less fuel

pwurple

I think the human behind the wheel is a large factor in fuel consumption.

Myself and husband tracked fuel consumption for a few years on different vehicles. My driving style is less fuel efficient than his. After a while on our graphs we could tell who was driving which vehicle each week from the usage.

I notice it more the with readouts on electric vehicles. When I put the foot to the floor to zoom up a hill or do some overtaking in an EV, I see a host of feedback telling me my efficiency is decreasing. I see my range dropping, my battery usage bars light up all the way to the right, my k per kwh reader drops. There are at 4 separate readouts displaying it on my dash. That same feedback is not displayed in an engined vehicle, so it's less intuitive.

dr.fuzzenstein

jimgoose wrote: »

I had a NA 1-litre back in the late '90s that routinely returned around 22MPG.

How was it for Smiles per Gallon? :pac:

jimgoose

dr.fuzzenstein wrote: »

How was it for Smiles per Gallon? :pac:

Ooooh, lots! 70MPH in first gear, anyone?? :D:D

H3llR4iser

jimgoose wrote: »

Ooooh, lots! 70MPH in first gear, anyone?? :D:D

Something tells me your vehicle had two wheels less than the others we're talking about here

Anyway, 1.9 Natural Aspirated petrol here, 160Hp - recent round trip, about 550km motorway + 50km urban driving and the OBC stated "8.6 Km/l". Clearly...ehm...a lot of headwind, both directions! It just works against me, I swear.

With not so much...headwind, I've seen the number creep up to 10, sometimes 10.5. It tends to be relatively accurate with real consumption...and I couldn't really care much.

That said, the 1.4 I had before returned similar figures, if not worse. It's the friggin' foot headwind, I tell ya!

billy few mates

I have a 1.2tsi VW Golf, I do a mixture of urban and motorway driving at the moment and I get a pretty constant 48-50mpg....