ORIGINAL: Blackflag
Well, you can't compare across vehicle lines because there' are too many variables. And you can't fairly compare two different engine families, because there are too many differences between the two. (For example, your Chrysler comparison compares a 3.3l to a 3.5l, which accounts for the fuel economy difference in itself.)
But on a single engine family, multiple valves will generally give better fuel economy because of the more efficient cylinder filling. Volumetric efficiency increases over two valves, which virtually dictates better fuel economy. However, nothing is absolute. (You may put on 4-valve heads with a cam that is far less fuel efficient and lose the benefit.) But it's pretty well understood that four valves = better FE. A good compromise between performance, FE, and emissions is the three valve arrangement, which MB and Ford have kind of settled on. Two valve is a little dated/cheap in my opinion.
Okay now I think we have found the route to your problem with the Hemi. You don't like it because its a 2 valve per cylinder pushrod engine. Funny how when you first joined the site, you were bashing the Hemi saying it wasn't a true Hemi, then you want to make it even less like a Hemi by going 4 valves per cylinder. Amusing but not quite as amusing as your response.
A little background info for you Blackflag. The 3.5L is based off of the 3.3L. They are from the same block. Essentially, you have just argued that the Chrysler 3.5L is from a completely different family than the 3.3L and that explains why it gets lower fuel mileage, so then if a 7.0L Hemi would be produced with 4 valves per cylinder and OHC with the 5.7L/6.1L/6.4L block, would it be become a whole new family? No, its called they switched the engine from a pushrod design to an overhead cam 4 valve head which is all that happened to the 3.3L base when they made the 3.5L. The 3.5L had the same axle-ratio (3.66), same transmission (A606/42LE), same platform (LH), same vehicles, higher compression ratio (depending on the year 10.4-9.4 vs. 8.9 to 1) which improves fuel economy mind you, etc. as the 3.3L, so explain all the other mystery variable that have not been included. If your argument was sound, it would at least be able to maintain the same fuel mileage despite all of this.
Also the same thing is true about the 3.4L DOHC engine, it was based off of the GM 2.8L/3.1L/3.4L block, they just made an OHC out of a pushrod is all that happened, and that is exactly what would happen here if they made a 4 valve DOHC Hemi. Same procedure
How about more examples about how your argument is wrong? The early Saturns had the 1.9L engine in either 2 valve SOHC or 4 valve DOHC. A SC1 2 valve SOHC model would get 40 mpg when equipped with the 5-speed manual with an axle-ratio of 4.06; meanwhile, when it offered the 4 valve DOHC which according to your argument should improve fuel economy only got 37 mpg when equipped again with the 5-speed manual transmission and the same axle-ratio of 4.06. How about more examples, the GM 2.3L Quad-Four when 2 valve SOHC 5-speed manual 2.84 axle ratio equipped got around 33 mpg in the earily 90s Grand Am; however, the 4 valve DOHC version only got 30 mpg with the 5-speed manual and 2.84 axle ratio combo. Two examples of a three mpg drop with the same sized engine, both originally OHC designs, same gearing, same transmissions, same car. etc. The problem is there so far no proof of the opposite happening anywhere.
Each of the other examples demonstrated in my previous post showed how even though the 4 valve DOHC engine had the gearing advantage, new technology, same platforms, etc. each time it got lower fuel mileage. It appears your theory is no longer a theory because it has been proven to be incorrect over and over again.
Out of all of the different car companies in the world, the last two I would ever use as a benchmarker or one t