I have heard that about the new age oil, seems to stay on the motor parts better than the old school oil... Makes sense I guess, especially on cold start days when the oil is mostly in the oil pan.

 

I'm a Valvoline guy. Been that way since my first car. Dad was a Valvoline guy, so that's where it came from.
That's what I run in my Blazer and wife's Buick.
I'm going to give Mobil 1 syn 5w30 a try, though.

 

Same, except my dad is a Castrol guy, so now I'm a Castrol guy lol

 

I'd been considering this since I saw that AmazonBasics now has full synthetic SN-plus for $19.99 per 5qt and store brands seem to be coming down to match it. I did some research and asked the owner of the shop I take mine to. The obvious but obnoxiously correct answer is of course: just use whatever you've been using, and preferably what the manufacturer recommended. But what fun is that?

I don't claim any expertise and would appreciate corrections but so far I have learned:

1. Synthetic is better oil, lasts longer, protects engines better, sludges less, cleans better, coats better, and is quicker to spread on cold start to guard against wear.

2. Older engines like these can't take advantage of all the benefits of synthetic though. Power and economy especially will be pretty similar.
2a. In particular the service interval can't be extended lots since oil changes also serve to remove contaminants that newer engines are better designed to keep out of the oil; in these old engines it was assumed that oil changing would take care of it periodically instead.
2b. Using a quality filter (Bosch, Mobil 1, WIX/NAPA gold, Purolator etc.) might help extend the interval some but is not a substitute since the filter only catches things larger than oil molecules (Yes, that's an oversimplification but a good filter isn't everything)

3. Since synthetic does a better job of cleaning, switching can -- at least temporarily -- lead to leaks and oil burning as old deposits etc. get expelled. Some of that old dirt might be in there helping hold stuff together now. Depending on the problem this may lessen with time as old deposits get burned off and/or removed with subsequent oil changes.
3a. This may be heavily dependent on how well the engine was maintained in the past or by previous owners, and might even just be uncovering a problem that was getting ready to happen anyway
3b. Switching to synthetic oil ain't gonna fix a neglected engine

4. You can mostly switch back and forth between synthetic and conventional without issue in these, especially once old contaminants and deposits get worked out. Doing so might complicate troubleshooting though.

5. One thing I read (can't find the source, sorry) recommended first switching to a semi-synthetic blend (or just adding a quart of synthetic to a conventional change) at least temporarily to help mitigate changeover issues or at least spread them over a longer time interval.
5a. But at the same time, depending on who's asked blends are a crummy compromise, providing neither the economy and predictability of conventional nor all the benefits of full synthetic.
5b. There are a lot of strong opinions about oil on the internet, and some of them are contradictory...

6. You *CANNOT*however switch back and forth between regular and High Mileage (with either conventional or synthetic). Once you've fed it High Mileage you have to keep doing so, since the high mileage additives cause seals to swell and then wear in to the new dimensions. If that new diet of seal conditioners is removed they return to normal and might start leaking/burning oil even if it wasn't previously.
6a. So you should not switch to High Mileage unless you're already leaking/burning oil from places not easily fixable

7. SN-rated oil is great, SN-plus is basically no benefit for those of us without a turbocharger or such.

8. Frankly, I'm mostly of the opinion that any SAE/API-certified brand of oil in these engines is fine, and brand matters a whole lot less than the type and adherence to upkeep and service interval, but that's just opinion.

Since I've decided now to go back to changing my own oil (I know, long story) and have owned mine from new and know its history I've decided to try a blend my next oil change and see what happens. If I'm not smoking or leaking I might then get an oil sample analysis done at 5000 miles and decide what to do from there. To do a more deliberate experiment I'd probably need to do a sample on conventional first, but the effort and budget required kind of outruns my interest in it really.

 

That was a great in depth post Rock18... I definately use the high mileage stuff every 3000 miles come "heck or high water"

 

Hey, no prob. It's mostly thoughts I'd been collecting and thinking of posting here anyway.

This is another of those "depends on who you ask" kind of things, but it's generally regarded that a 3000-mile oil change interval was excessive for these engines with modern oil even by the late '90s, since that was the same thing that had been thoughtlessly recommended for decades previously for older engines running straight dino base oil with no additives. If you're doing lots of extreme duty like towing in extreme conditions (in which case you should probably be using something else besides a V-6 SUV to do so, but anyway) 3k might be appropriate, but otherwise with modern oils you're probably fine with a service interval more like 5-7k instead. This was pretty much true even when these engines were new too, and GM probably only stuck with the 3k recommendation out of inertia and for liability and CYA reasons especially once they started with Dex-Cool. Personally I usually go to 4,500/6 months and then try to find a convenient time to change, and have only approached 7k a few times when I've been excessively busy. And I've gotten to 163k miles and 19 years come this June on the original engine this way, and not leaking or burning anything.

Again, if it makes you and your truck happy to change at 3k then go for it. And if you've been feeding her High Mileage and it's working you should keep doing so. But you might be able to do so less often and keep more money in your pocket for other stuff.

 

I hear ya! Funny how things get "beat in your head" over time, "you better do this, you better do that" kinda thing growing up lol

 

It actually is really important to brush & floss though.

 

Awwwwww mommm, do I have to...........