S5 4.2lt V8 realistic figures please

Hi all,I am looking at S5 V8s. I currently own a shark performance stage 3 2009 Audi S3. I have been looking at 2009 Audi S5s, the V8 version.I am getting 23mpg average at the minute so it's not like it's economical, I never see 30mpg .I'm not expecting the S5 to be any better but if you lot say you can get high teens/low twenties I'd be very happy.Also, I know you'll all be biased but, will I regret going from a 350bhp turbo S3 to a 350bhp V8 that is bigger and heavier.As you can see from my sig, and my business banner, the 5s are one of my favourite cars...Thanks in advance...

I don't do loads of motorway miles, I do have a mix of town and motorway miles on my commute.I don't hoon my S3 every or throw it round corners. I usually drive steady and leave off the power until having a quick blast down the motorway.I think an S5 suits my driving style more, the looks, well it's one of the sexiest looking cars ever and one of my realistic dream cars if I'm honest...V8 rumble is very, very appealing.I am into modifying my cars and I know N/A aren't as tuneable but what can be achieved from these cars that isn't a turbo strapped to it. These are the same engines as the RS4 aren't they running at 400plus bhp.

Thanks Pete...

I've had my S5 3 weeks now.

I'm getting 17.5 average and 24.5 if i take it easy.