is el capitan recommended for an early 2008 imac?

is el capitan recommended for an early 2008 imac? | Official Apple Support Communities
El Capitan uses 4.5G of ram or more on my iMac just surfing the web. Yosemite used an average of 2.4G or so doing the same things

6 Steps to Prepare a Mac for the OS X El Capitan Update
If the Mac is running OS X Mavericks, OS X Mountain Lion, or even Mac OS X Snow Leopard, you’ve got a tougher decision to make, mostly because you likely stayed on one of those earlier releases for a reason.
Will OS X El Capitan offer a meaningful improvement over what OS X Mavericks or prior offers?
Feature wise, of course it will, but sometimes new features matter less than whatever kept the user on a prior OS X version to begin with, whether it’s app compatibility, avoiding iCloud, the font and UI changes, or just operating under the popular mantra of “if it ain’t broke, don’t fix it”.
Thus some of these Mac users may just want to stay put on the earlier version, assuming they know that by doing so they’re going to miss out on various new features, security updates, and compatibility with future versions of some apps.
This one is really going to be up to the specific user to decide, but if you like your Mac the way it runs now, it’s not a big deal to stay where you are.

Another approach for those hesitant to jump ship to a new system software update is to wait for the first point release, in this case, OS X 10.11.1 El Capitan.
That point release update is already in beta, and will likely be finalized over the coming weeks/months as various bugs are patched and refinements are made to OS X 10.11.
This is a perfectly reasonable update strategy that many Mac users employ, so if you don’t mind being a little bit conservative with your system updates rather than on the cutting edge, perhaps wait for OS X 10.11.1, or even OS X 10.11.2 before updating the Mac, there is absolutely nothing wrong with that.

Confirm the Mac Meets Necessary System Requirements
OS X El Capitan is pretty forgiving for system requirements, and the OS X 10.11 compatible Macs list include any Mac that is able to run OS X Mavericks or OS X Yosemite, offering a wide range of support.
That basically means any Mac model from late 2008 or newer should work just fine with OS X El Capitan.

In other words, you do not need to install OS X Yosemite before updating to OS X El Capitan, you can upgrade directly from OS X Mavericks to OS X El Capitan simply by downloading the installer from the App Store and running it on a compatible Mac.

- complete a backup of your Mac before installing those.

If you haven’t set up Time Machine backups on the Mac yet, you should get an external hard drive and do that.
Whatever you do, do not skip backing up your Mac.

Good to go? Install OS X El Capitan!
Installation is very easy, it’s just a matter of downloading the update from the Mac App Store, pointing where to install (usually Macintosh HD), and letting it run. Installation takes about an hour or so to complete for most modern Macs, but it can take a bit longer depending on the speed of the Mac and other factors.