Specific question regarding oil

Questions here that are probably gonna be divided, like I see searching on google....

My rig is an 06 yukon.
Bought the truck about 6 months ago with a little over 200k on it and have only put on another couple thousand but its still over 200k.
The reason I bought this particualr one is it had been very well maintained and I see and have all the logs.
I asked the owner what oil he uses and he said he's always used conventional, not synthetic and once or twice a year runs a bottle of techron.
In addition, he's replaced a lot of the usual things and has knock sensors and other things replaced, the reason I mention that is I assume its pretty clean in there without a lot of sludge, especially with all the regular oil changes though this is just a guess.
I have been topping off with either a blend or a full synthetic.....
Now its time to do an oil change..I also have some occasional lifter ticking is what it sounds like

Thats the background so not the questions:
1. There are no leaks anywhere...he has always used castrol conventional 5w-30. In doing an oil change should I stick with conventional oil....brand aside should i go to synthetic? I hear pros and cons of both. The whole debate on conventional oil sealing everything better so no leaking .....
I also was planning on doing sea foam before the oil change to clean things out and help stop the ticking though is that gonna cause an issue if there is sludge in there and the sea foam cleans it out are things gonna start going south for me and worse yet, I caused it?
I cant afford problems or repairs so im asking to avoid any trouble.

What is my best course of action...do i use the sea foam or not.....do i use conventional or synthetic.....anything else i should do or dont do.....already have an acdelco filter

Thanks

Yep, there's gonna be a smorgasbord of opinions. Here's my input after being a tech for 25 years.

I don't believe that full synthetic dexos oil was required in 2006, just regular 5w-30. I would personally stick with what was used up to this point. If service intervals were kept on a good schedule, there really shouldn't be all that much sludge buildup in the pan. There is always going to be SOME because it's and ICE.

I think that switching to full synthetic may end up washing things cleaner, maybe affecting seals that are borderline by finding a way past, etc. Unless you live in a consistently frigid climate, you aren't going to gain much from synthetic vs Dino oil. Yes, it does have higher temp ratings, but again use common sense and change as needed.

As for the sticky lifter, just throw 1/2 quart of cheap ATF (DEXTRON 3) in the oil for the last 500 miles or so and drop it. It will help clean up varnished stuff, but not be overly aggressive. I've had good luck for many years doing this. It also works as a good fuel system helper for vehicles with older injectors (1/2 - 1 qt per full tank)

To make an overly long story somewhat shorter:
0W30 (brutally cold winters) or 5W30
Group 4 synthetic oils change every 4-5000 miles, or 5-6000 miles if enough of the miles are highway.
Non-Group 4 motor oil change every 3-4000 miles, or 4-5000 miles if enough of the miles are highway.
Change oil & filter at least yearly, before either the coldest or hottest month, whichever is more brutally so.
If you fear sludge buildup, change the oil even more often than suggested.

'Conventional vs synthetic' debate is beyond outdated and wrong, like 'exhausts need backpressure'.
Use PCV thingy 12572717.
Every time the engine is cold-started, best for the engine to keep working for at least 30min.

If it's consistently running rich, find out why. A catch can is a good investment, buy a good one.

Thank you both....Marky for the info and B-train for the solutions.
B-train, everything you said is the exact way I was thinking...wanted to hear it from someone more experienced though. My only follow up question is with the ATF routine for both the oil and to clean the fuel system...I was gonna use the sae foam for both of those....the oil part I know its dump in 1/2 quart, but is really 500 miles? I cant wait that long...maybe 50 - 100 miles, the sea foam recc. is about that. So will the ATF still do its job at 50-100 miles or should I go with the sea foam?

If it was me I wouldn't change a thing. That Castrol is good oil. Changing brands or types, especially adding some cleaner to the oil is asking for trouble. I'd bet if you were to pull the valve covers and intake you'd find a pretty clean motor even at this mileage. I might think about pulling the valve covers and with the engine running listen real close for any noise at a rocker arm, and check that one real close for anything unusual.

well, i guess ill segway a little into that.....its a ticking noise....it can happen cold or hot...it can be silent then i accelerate and i hear it loud....i let off the gas it pretty much goes away....then all of a sudden it wont do it no matter what i do and come back a little while later......does that info point at something specific?.....
i dont have the money right now to take things apart, pay for erroneous parts or open a can of worms and make things worse...just want to do the right things with the oil and was hoping to kill 2 birds at the same time

Might not be a lifter. Might be an exhaust leak.

Oh. Forgot to mention, use the longer-bodied oil filter.

B-train said:

I would personally stick with what was used up to this point.

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tom3 said:

If it was me I wouldn't change a thing.

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XXX3!!! ^^^^

No additives and quit using the synthetic for topping off.

Marky Dissod said:

Might not be a lifter. Might be an exhaust leak.

Oh. Forgot to mention, use the longer-bodied oil filter.

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didnt have it so i bought the short one....why the long one?

swathdiver said:

XXX3!!! ^^^^

No additives and quit using the synthetic for topping off.

Click to expand...

Not even the ATF in the oil or fuel?