AutoblogGreen

Good move. My Saab 9-3 has a 2.0 turbo four(175hp) that gives decent performance and very good mpg. I average 32-33mpg everyday. On long highway runs I have averaged as high as 36 mpg all on regular. A 1.4L in the Cobalt and Astra should easily get 35 mpg. Put a turbo 1.2L in an Aveo and 40 mpg is very achievable.

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Will the turbo require premium fuel?

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"require premium" what a blown statement.
After buying my 9-3 2.0t I did some poking around about what fuel was 'required'. the best answer I read:
If the car is sold with the same engine in the majority of the world then you can disregard any high octane requirement - you can use the lowest octane available (of course engine knock isn't the best so choose good fuel)
reason - anywhere outside north america and europe access to clean high octane fuel has been almost non-existant (many regions still sell lots of leaded fuel - so at least stick to unleaded)
Sure high-octane may keep your engine in better condition over the life of the vehicle (200,000+ kms), it will likely also give you better performance. There are stories about fuel economy too - I haven't found there to be enough of a difference to warrant the price penalty.

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I use regular in my 2005 9-3 2.0T and have had no problems in 83K miles.

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GM is beginning to reap the rewards of creating a global powertrain division. For developing these small, relatively weak inline four GDI engines, the company has more expertise in Europe than it does in the US. Also, there is currently an R&D trend toward parallel twins and inline threes with inertial compensation and variable or dual boost systems, though it is not clear that GM will participate in it.

By contrast, Ford USA is only just beginning to leverage its European subsidiary in this respect. Chrysler doesn't even have that option now that Daimler has sold most of it to Cerberus. The 20% remaining stake will probably not translate into transfers of technology that Mercedes-Benz considers vital to its differentiation in the market. After its decision to halt further development on its HEMI V8, Chrysler will have to develop downsized turbocharged gasoline engines on its own, or else buy them from either a another car maker (e.g. Citroen PSA) or the supply chain (e.g. AVL. FEV, Ricardo, Mahle).

@ Bill -

all modern spark ignition engines feature a knock sensor, basically a type of microphone attached to the crankcase and software that evaluates the signal. Not all knock events are equally serious, but if things get out of hand the software will ensure the ECU retards ignition timing to avoid damage to the engine. Therefore, you can run an engine designed for e.g. 98 RON fuel on 95 RON fuel as well.

It's just that the retardation will mean your engine will no longer quite deliver rated power. Retarding the ignition also means you use more fuel. That pretty negates the cost advantage of the cheaper fuel grade. Moreover, exhaust gas temperature goes up, so operation near rated power on inferior will lead to severe enrichment of the mixture to protect the turbo and three-way catalyst.

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Driving around with your timing retarded by the ECU is not only bad for fuel economy it will shorten the life of the engine.

The "good news" is that E85 is high octane and it appears to be widely available in the USA.

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@ tankd0g -

actually, E85 isn't widely available outside the Midwest. Even there, far from every filling station sells it. Besides, corn ethanol's environmental credentials and subsidies/protectionist tariffs have been called into question. The state of Michigan just allowed a tax break for E85 to lapse.

Moreover, certain fuel system components have to be upgraded to support E85, which is chemically more aggressive than gasoline. No such modifications are needed if you simply fill up an inferior grade of gasoline - even if there is no real upside to that. You are comparing apples and oranges.

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While you might not be able to use E85, if you had access to E-85, you could mix 87 and E-85 in an 75-25 mix (E25) and get a fuel with enough octane to count as premium. Considering Brazil uses E20 with in gas cars with no modification, pushing it to 25% without problems seems likely.

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What's the point of exactly the same HP rating as the 1.8L?

Slightly better mileage?

Why can't we have the already in production 1.6L turbo?

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Well, I'm a happy owner of a Spanish-built Opel Astra 1.4L 1995. My car consumes 1L of gasoline to 13km which is about 30MPG.

But I would advise not to buy 1.4L if you need an A/C...

And I'm sorry that nothing came out from this:
http://www.autoblog.com/2005/01/09/detroit-auto-show-opel-astra-diesel-hybrid/

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The Honda Civic 1.8 'requires' 95RON fuel for maximum power.
http://www.worldcarfans.com/2070129.006/page8/honda-civic-type-r-and-type-s-in-depth
VW high output twincharger requires 98RON, the lower powered one (sans supercharger) only requires 95RON for full power.

SAAB's overboost function requires premium fuel.

and the % difference for the fuel grades is shrinking as the prices go up.

The only time I saw an accurate differentiation of the fuel grades was about nine years ago, when regular was $2, mid-grade $2.25, and premium $2.5.
I guess that was too much work for the gas stations. The gas widget says 3.08, 3.18, 3.28.
Buy be a cheap*ss, at least get mid-grade.

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"But I would advise not to buy 1.4L if you need an A/C..."

GM can probably solve this problem with their next gen BAS mild hybrid system. The A/C compressor can run from a separate electric motor run from brake regeneration and the promised lithium ion battery pack.

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