As a sim builder/admin I have a tendency to rant on this subject, but I feel there's value to explaining the subject for any who are maybe a little hazy on SL performance issues and how to resolve (or not) them.

If you're not familiar with it, under the avatar menu, avatar health subsection there is a lag meter option, open this up and have a look. At a glance, the lights will either be green, yellow or red for each of 3 metrics. Green being good, yellow is problems, red is bad/major problems.

The category "client" represents how well SL is running on your computer, that's not to say it isn't being affected by things the server is sending it, but effectively the problem is at your end, we'll get into this more in a little.

Next, we have network, on rare occasions, this will represent a problem at LL or internet connection issues generally. Yellow and red are most often indicators that either one of your network settings is wrong (like your anti-virus program is blocking SL, you'd be surprised how often this happens) or you've just teleported/logged in and SL is trying to load everything at once and it just can't get enough data through all at once. Seeing yellow or red flashing especially when you're moving around is normal, if they stay that way when you're standing still check your connections or network settings (sl bandwidth throttle can affect this).

The bottom light is server lag, this is telling you if the sim itself is running slowly. If this is persistently yellow or red that represents either a problem with LL or major server load issues. This would be the one where too many scripted objects could cause a slowdown. However, if you're watching the indicators 9 out of 10 times someone talks about "server lag" the server is fine, it's client lag. There is however an exception to this, servers take a big processing hit whenever a new client connects to them, IE tps in from elsewhere, or logs in. This is often the cause of "lag spikes" and sudden rubber banding, it's also a big part of why your car may shoot off into space when you try to drive over a sim border. Unfortunately that last is a tech issue only LL can fix, the best we can do to help is not login/out or tp in and out unnecessarily. If you're hosting an event and sending out TPs be aware you're likely making smooth play impossible, this is why having event venues off of the crowded sims is a huge help when possible.

So back to the client lag since that's what most of us are actually experiencing, what can you do about it? To start with turn your draw distance down. If you're not running an RTX based graphics card you might want to turn off the more advanced lighting effects too as they all use raytracing and your card will have to do that in software (slow). Clean up damn prims, I was camming around the other day and found several hundred prims worth of stuff underground/hidden/so tiny no one knows it's there. The prim count isn't the problem, but some of these have scrips, all of them had multiple high res textures and no one even knows they're there, but your graphics card does and so does your network traffic.

And then the painful reality, the worst offender by far is many of us. If you're not aware of your avatar render cost check it out some time. Go to avatar -> avatar health again and turn on show avatar complexity information. This will show complexity information above avatars, the complexity value is an indicator of how hard it is for a graphics card to draw that avatar. For a frame of reference, most mesh avatars with clothing and common attachments weigh in at 60k-100k complexity. However, it's not unusual to see several on CD with over a million complexity (I've seen as high as 3 million), meaning it's taking your computer as many resources to render that one avatar as 10 other average avatars. That sim lag when someone connects that I mentioned before, complexity plays a big part of that, as does the next thing.

Script weight, every script on every item your avatar has equipped (including your hud) adds to the total scripts running on the sim, while it's true they use less resources if they're not actively doing anything, if they use a hud or have verbal commands they are constantly running a "listen" script, also avatars refresh scripts much more often than static objects, so in short, it's not the cars causing lag, it's the people with scripts. This compounds when you're talking about that log server stutter because the server must load ALL scripts equipped on you all at once before settling down to only run those that have continued activity.

So, while I'm not saying we should name and shame or have hard and fast rules on these things if you want to help out the sim consider removing scripted stuff you're not actively using, making a copy of script modded clothing/hair so you can descript it. Check out your avatar render cost and if you're at the high-end experiment to figure out why most of the time it's just one poorly made item (necklaces are notorious for this).

And finally... pester nadir until he cleans up the mess or deputizes someone to do it.

/rant