Will a 2008 C300 achieve 30mpg???

I know these cars have just come out and time will tell how they do.  With a low drag coefficient, 7 speed automatic, these cars SHOULD achieve 30 mpg on a trip if driven normal. We are not talking a large displacement engine here. I know they are rated at  25 mpg, which seems awfully low for that car. The big V8 cars are getting in the low 20's on the highway, so there should be a difference. My 1978 5.0 SLC is capable of 21mpg and it is OLD technology.  The reason I ask is that in another year or two, I might be in the position to buy a new car and this might possibly be in my price range.  At the same time, I want something that will achieve 30mpg on the highway and low 20's in the city.  I drive a Volkswagen TDI, so I am a bit spoiled on the economy part. IF Mercedes would do a diesel C class that would be grand, but it does not look hopeful that they will do it for the USA anytime soon.  Or, sell the C with their DiesOtto motor which will nearly achieve diesel economy and it runs on gas. Time will tell what I do, if I am able to get a car in that price range new.  I will only do it if I do not have to go in debt making car payments!  Then I may go with Another TDI Volkswagen, but I am waiting to see if diesel prices will finally stablize. Also I would prefer to have a rear wheel drive car.  When diesel straightens out and Mercedes launches a C class diesel, they will sell many.  One other thing is, do you REALLY have to run Premium gasoline in the new C300, or does it have a knock sensor that will allow midgrade or regular??  I know some of the older BMW's required high octane, but you could get away running the cheaper grades. I had a 1991 BMW and it did not seem to make a great deal of difference. However the new Cadillac CTS (which is a competitor to the C Mercedes and 3 series BMW) will run on regular fuel. Anyway, I got plenty of time to watch things if this will happen in the future.  I am kind of a wait and see person. I like for all of the bugs and glitches to be worked out of these new models as well. Any information, insight is greatly appreciated!  Paul

If I may comment.......and pardon the bluntness of this reply. It's not meant to be that way, just an honest reply, OK?

I am almost sure that the new car you describe will achieve that mileage figure. I you aren't buying for another year or two,
you'll have plenty of time to ask on this site if owner's of that car get that kind of mileage, right? OK>
The argument of premium gas vs. regular gas is an old one. Most cars that require premium fuel will physically run on regular.
That's true. But consider this: the octane required is determined by the compression ratio built into the engine or the need for
premium fuel if the car has a turbo or supercharger. Putting regular gas in a vehicle built for premium is like drinking decaf instead
of caffeinated coffee. Looks the same, but the result is completely different. The engine won't perform
the way it was designed to, especially in cases where you might need to call on extra power. Sure, it will go down the highway on
regular gas. But everything else will suffer. So...... one might make the argument that if you spend the money on ANY car that requires
premium gas, you should put premium in it as "part of the cost of owning that particular car". And, that's the way I see it.

Incidentally, Mercedes Benz dealers here in my city have eliminated the risk of putting regular gas in their loaner cars by the customers
who were asked to fill the tanks back up after they used the cars. The customers would frequently top the tanks back up with regular gas
and as the service mgr. told me, it created such problems with the cars, they actually had to stop that plan and just have the people at the
dealership put gas in the cars there. So go figure.

Again, this isn't anything but my opinion and I'm not scolding anybody about what they want to do with their own car. I have built many
engines in my life and continue to do so as a hot rodder of American cars, both old and new. I run these engines on the dyno after I build
them and see basically the same thing.....octane and timing determine performance....period. I build engines to run on a particular octane.
This decision is made long before I start buying parts, such as pistons, cyl. heads, supercharger, etc. Then, whoever gets this engine is expected
and knows what octane they will be required to run in that engine. It's that simple.

I own the 2008 C300, I picked it up in Stuttgart on 21 September.  I have over 5000 miles on the car and I have yet to get 25 mpg.  Maybe it's the way I drive...oh, and the speeds over here vs. speeds in America.  I suppose if you drove 55-75 mph for long periods of time you'd get 25-30 mpg.  I agree with the other poster, if you are buying a MB, you really should not be concerned about what grade of gas to buy.  If gas prices are a concern, maybe buying a hybrid would work better for you.  I drive 80-100 miles a day.  I'm at the gas station every 2 1/2 days.  I am loving the car though!

i've had the c300 for about 1 1/2 months.  made a 400 mile trip to upstate new york my 2nd week.  i averaged about 26.5 mpg.  i was doing some where between 60 and 75 mph.  if you drive 55mph, i'm sure you could reach 28 or 29 mpg.  30mpg with this engine (3.0 liter 228hp) would really be pushing it.
 
if gas mileage is really your concern, take a look at an audi a4 with the 2.0t.  i was able to squeeze 39mpg at 55-65 mph with my old '03 1.8t.  the newer 2.0t is supposed to get even better mileage than the old 1.8t.

On my 2008 C300, i drove a 360 mile trip with avg speed of 75 and i got 28.5 mpg

i have a c300 sport 4 matic and i only get about 19mpg with moderate driving 80% highway, i love the car but even when i baby it i still cant get close to the 25mpg on the window sticker, other than the dealer having to replace the left cylinder head at 900 miles i love the car

Why did they have to do change the cylinder hear at 900 miles?
 
People who buy these cars should understand that these are luxury vehicles. They're not built to be light weight gas sippers, they're built like a tank to limit different road deviations, for safety and reliability. With a heavy car and a heavy soft suspension, needless to say it's going to have a better ride. Where as with Honda you're buying a light panel car that can acheive better mpg's using a buzzy little engine. With the C300 I see a lot of people on other forums getting about 27mpg on average, which is good for the M104 V6 and a heavy car.