Safari killing memory on Mac

Safari does use a lot of RAM (but all modern browsers do) and 4gb isn't much to start with. Perhaps you could upgrade your memory? Which model Mac is this?
(If you're not sure, go to the Apple Menu and choose About this Mac. send us that first line. mine is MacBook Pro (13-inch, Early 2011)

Late 2009

Pretty normal these days.

Some websites are memory hogs, Facebook easily sucks 1Gb.  Under Chrome, IE or Edge on a PC, with a dozen tabs on my "travel" laptop with 6Gb I can easily use all physical ram.  You might have to get more RAM, or accept that you can't run a lot of complex browser instances at once.

But it used to work good before so I dunno if is something else??

So in your opinion you need a pc with at least 8 gigs of RAM???

Yeah, with 8Gb you should be able to open a heap of browser tabs and be fine. 4Gb is useable, as long as you keep an eye on usage and don't have too many ram hungry sites open at once.

Assuming you mean "MacBook Pro late 2009" then I'd suggest this ram upgrade:
http://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade/DDR3

Over time, as applications and operating systems "improve" they take more memory for the same thing... sot that would definitely explain the observation that "it used to work fine" as well as the previously stated fact that websites are getting more complicated.

I'd also suggest some plugins that reduce the amount your websites are allowed to do, like: Adblock and click-to-flash. That will help a little.

Also check that you have ample space left on your hard drive. That could be a factor too.

Macbook not pro

Okay, well then click the "more info" button and figure out the model identifier. If it matches one of these, that's still the right ram:
Works with Model Identifiers: MacBook5,1; MacBookPro5,1; MacBookPro5,2;
MacBookPro5,3; MacBookPro5,4; MacBookPro5,5; MacBookPro6,1;
MacBookPro6,2 & MacBookPro7,1

If not, it will be this:
http://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade/Macbook_selector

It says Macbook 6,1

Ok but according to crucial website my Macbook only supports 4 gig maximum so how come these other sites telling me I can use 8???

apple also says 4 gig max so i am a bit confused.

https://support.apple.com/en-us/HT1651

so i talk to a rep in OWC Sales and this is what he said

Apple does not go back and retest Macs when larger modules become available.

So i guess you are right then.......

Yes, Apple is quite conservative with this stuff. I've upgraded dozens of old mac laptops to specs higher than Apple's and its fine. OWC is a great company who stands behind their products, too.