91_RED_Z28

OK so I have a 91 Z28 with about 206,000miles on her...now I have been using 20W-50 conventional oil for the most part of those miles...now could I change to synthetic oil without having any problems...or am I going to have to do a complete rebuild in order to change oil types?

84Z28406

Synthetic will be fine, but if there's sludge blocking any possible oil leaks, the higher detergency will strip that away and allow oil to leak.

Darkshot

iTrader: (4)

If you've managed 206,000 miles just doing what your doing, I think you'd be a fool to change anything at this point.

five7kid

iTrader: (14)

It won't necessarily leak. But, it might.

Instead of a complete change, just use one quart of synthetic and the rest conventional first. Then the next change (might want it to be a little shorter interval), use 2 quarts synthetic. Then 3 quarts, etc.

By the time you're up to a full synthetic change, you'll know if you've got a problem or not. Most likely, you won't. If leaks develop, change the gasket or seal that's leaking.

Why 20W-50? Way too thick. Just stick with 10W-30.

What brand conventional have you been using? And, what brand synthetic are you considering?

safemode

iTrader: (1)

The only way synthetic can cause a leak to occur is by removing sludge that was previously blocking an older leak. I dont see what gradually changing into synthetic will do for him. Either the leaks exist or they dont. They wont get any less leaky if it's 1 part synthetic vs 100% synthetic, if the sludge is cleaned away, it'll leak...like it is supposed to.

The bigger problem here seems to be why he's using such an insanely thick oil for a car that doesn't sound like it's built to require that oil at all. He's in cali, so the 10w makes some sense, but the cars were built to work with 5w30, and if you're using synthetic, unless the engine is used primarily for racing, 5w30 full synthetic should be perfectly fine even in californian heat, and it should give you better gas mileage as well. I have a feeling that since he's using such a thick oil now, no matter what kind of oil he used, going to a thinner oil will probably result in leaks showing up. Some people like to use a thicker oil to hide a leaky gasket problem (burning oil out the tailpipe).

formula_novice

iTrader: (1)

Not trying to hijack the thread, but I had people at Autozone and O'Reilly both tell me that if I switch to synthetic and there is any left-over conv. oil in the engine, it will turn to sludge when the synthetic hits it. From what I read above that is not true???

Another rumor I heard is that, if the car has a lot of miles, switching to synthetic might cause any sludge "helping" to seal the rings get removed thus creating an oil-burning scenario. Any opinions on this?

I'm not saying either of these situations are true... I've been thinking of converting my 160k 350 to synthetic but heard these stories.

Thanks!

Wadebryant

Why now?

safemode

iTrader: (1)

first, you have two opinions that are contradictory.

The autozone people are telling you that putting synthetic in a previously conventional engine will cause sludge to buildup and form.

The other rumour you heard says that synthetic causes the sludge to break apart.

The truth is that neither is true. It's the cleaners in the oil that can cause sludge to break apart. But the chances are, if you're using high mileage conventional oil, you already have cleaners that are strong enough to break sludge apart.

The other thing is, lots of people use a heavier than necessary weight conventional oil since thermal properties of conventional aren't all that great (especially in hotter climates). When they switch to synthetic, they use the correct weight oil and now they're putting something thinner in. This can expose leaks that previously didn't appear to exist (obviously they did though).

If you're moving from the same weight conventional to full synthetic, you shouldn't notice any difference other than less wear.

chesterfield

This topic comes up a lot about synthetic cleaning away the "sludge" that is keeping an engine from leaking. I have no data to back this up, but practical experience tells me this is a myth. I've seen a lot of grungy engines over the years and I've never seen this kind of "sludge" that is capable of sealing a gasket. Whether its oily "sludge" or crusty "sludge" it just doesn't have the body or integrity to be used as a gasket sealant. I've never seen such a build up around the rear main seal or the timing cover seal. The crankshaft is in a high rate of motion any way so a build up there could never seal anything (it may be the abrasives in said "sludge" that causes the wear that creates leaks in theses areas, not prevent them). I've also seen my share of leaky gaskets on engines that had plenty of "sludge" that never saw synthetic oil. If "sludge" is such a good gasket sealant then Permatex ought to market the stuff in a tube, because their current products lose their sealing properties as time passes.
Just one man's opinion.

Stephen

iTrader: (12)

I agree with the running of 20w50, especially in the hotter states.

It doesn't get cold here, so thicker oil isn't problem in the "winter". But considering the heat, starting out a little thick might even help too, IMHO.

I think between his 206,000 miles, my 190,000 miles, I'm sure many others too, not just us two)....That I've ALWAYS run that in ALL my cars & trucks, and that I've never had an engine failure, due to bearing damage....Kinda speaks for the validity of thicker oil not being a bad thing.

I Don't see the need to switch to synthetic, since conventional is obviously working well, and cheaper.

safemode

iTrader: (1)

It wont hurt so long as the temp doesn't get too cold. The thing is, it's not necessary either. The benefit of going with the thinnest oil for the job is efficiency. You lose a lot of efficiency by using an oil thicker than what is actually needed.

5w30 or at most 10w30 full synth should be fine for everyone not running a circle track or dealing with combustion temperatures much hotter than stock.

Viprklr

iTrader: (5)

I agree with 5.7kid.
That's how I did my conversion on all of my vehicles.

The thinking was that as the synthetic cleaned the "sludge" away that if you do it slowly, you wouldn't have any issues with plugging up your fuel filter or having anything break off and go somewhere it shouldn't.

Little safer.

safemode

iTrader: (1)

i think the idea that sythetic is like tranny fluid when it comes to cleaning is a little much. It's just highly refined oil. The cleaners that are in it, are similar in strength to the cleaners you'd find in any decent conventional oil.

If you're taking care of your car now with conventional oil, then you wont notice any real difference by moving to synthetic. What will happen though, is that any situation that would normally push the operating limits of oil to the extreme, will be better handled by the synthetic oil than if you were still using conventional. Be it temperature related or mean time between oil changes. That's it really.

five7kid

iTrader: (14)

Some synthetics are just highly refined oil. That is the case for most of the major wannabe synthetics, aka, the Group III synthetics (Valvoline, Castrol, Pennzoil, etc.). But, a "true" synthetic is "synthesized" - hence, the designation "synthetic". Group IV and V synthetics are synthesized from non-petroleum reagents. They are not refined, they are formulated. It was only our good ol' bureaucracy using their regulatory fiat that allowed the wannabe's to call their inferior product "synthetic" - the technically-challenged bureaucrat thought "highly refined" was basically the same as "synthesized", so today we're stuck with this ambiguity.

But, as Viprklr said, the reason for the slow change is to slowly dissolve and break up the petroleum oil deposits. If an engine has received regular oil changes with a quality petroleum oil, the deposits will be less than they would be if oil changes have been neglected and cheap oil has been used. But, there will still be deposits, and if heavy enough and broken up too quickly, you can clog the oil pump pick-up screen.

What I've typically seen is engines with heavy deposits from neglected maintenance also tended to leak. Regardless, the slow change-over also allows you to get the gasket/seals changed before you do the last change with full synthetic. For what that's worth.

Using the proper weight oil is wise no matter where you live. 20W-50 petroleum won't protect as well as a quality 10W-30 synthetic, even in hot climates. Using a wider band oil like 10W-40 is even worse, since the wider the spread, the more viscosity index improver additives have to be used - and VI improvers are one of the first things to break down and form sludge.

And, as usual, the very mention of "synthetic oil" has brought out the misinformation and emotions, which the informed and logical have to spend time to refute.

formula_novice

iTrader: (1)

Thanks everyone for the info! It's nice to hear opinions from people who have actually used synthetic versus the random opinions at the auto parts store.

Would it be worth it to get a conventional oil flush (such as the one from Amsoil) and flush all the old oil out prior to putting synthetic in? I know you talked about clogging the screens but wasn't sure if this flush would prevent that.

Thanks again!

safemode

iTrader: (1)

What i meant by "refined oil" was not the literal idea that all synthetic is simply refined from regular oil (even though some are as you mentioned). But that synthetic oil is no more special in how it functions than regular oil is. It just has larger operational limits, by being as uniform as it is. What makes synthetic oil special is that all the molecules are the same, and ideal. The additives you find in synthetic oil are barely, if at all, different from your quality conventional oils when it comes to cleaners, in fact most have less. So the idea that putting synthetic in will magically clean your cars engine is true, to a point, but that same cleaning would have occured with any quality conventional oil (like a high mileage oil). if you're already using good conventional, then it wont get any more clean than it already is. What will probably happen is that no more buildup is added to the sludge already there over time, and this will eventually remove more and more from the engine. But that would likely take a couple years to happen that way.

There's a good reason why they make flush kits for engines out of stuff that really sucks at lubricating, and that they tell you to only run it for a few minutes. The best way to clean out sludge is to break down oil, because that's what it is, and it coats the sludge the same way it coats metal.

I just dont see the vast cleaning improvement and consequential filter clogging happening on anyone's engine unless the previous oil was crap and the maintenance was crap. But the fact that they're now gonna put synth in has little to do with the fact that it's synth, and everything to do with now they're putting an oil with quality cleaners in it, which you get with any quality oil. The effect of synth on buildup takes a _very_ long time to be seen since it's the lack of new buildup that finally wears down the old buildup, and it can take many oil changes of full synth before that adds up to anything noticable.

kcb37

I have to argue with you at least a little safemode.
I will say this first though. My car was beat up and abused before I got it.
That being said, I ran conventional oil in in for the first two oil changes, didn't have a problem. Leaked a little.
Then I put Mobil on in it. It runs much smoother. However after about 4 or 5 days, the valve seals had started leaking so bad, it almost wouldn't start. I changed the plugs right before the oil, they were "clean", just old. Not a drop of oil on them.

five7kid

iTrader: (14)

safemode, you are a mixed bag of truth and error. Synthetic does have a more consistent molecular makeup, a wider operating range, and typically require less/fewer additives. While synthetic oil may not be any more "special in how it functions than regular oil is", it certainly does it better. And, that is significant.

The synthetic base is a more natural detergent. With petroleum based oils, you have to add detergents. Petroleum based oils may clean existing deposits at first, but they immediately start breaking down themselves and add more deposits. You can't clean something with the very thing that made it dirty.

You aren't "breaking down" the oil with a flush product, you are adding a solvent to the oil for a short time to break down the deposits. Solvents, like detergents, aren't good lubricants, so you don't use them for an extended time or under load.

formula, the AMSOIL flush is a good product. It not only is a solvent, but also concentrated detergents and dispersives. It will do the same thing as the increased synthetic change method I described, but in one shot. My preference when using it is to run the synthetic for a shorter than normal interval the first change, and use the flush again at the next change. What AZone told you is completely false - you aren't flushing the conventional oil out of the system before you put in the synthetic, you are cleaning out petroleum oil breakdown deposits before you put in the synthetic, which if you don't the synthetic will start dissolving, which will contaminate the synthetic oil. That's all that's going on. Mixing conventional and synthetic does not form sludge. The sludge comes from the petroleum based oil breaking down under heat and sheer loads.

safemode

iTrader: (1)

A solvent by the nature of what it is, breaks down what it is that it's dissolving. Not in the sense that it changes oil into something else, but it breaks the bonds that make oil attract it other oil molecules and surfaces that it's attached to. This allows it to absorb the molecules into itself to be transferred with the fluid to a filter or out of the car.

I dont buy into the whole synthetic oil cleans your engine better than say, mobil 1 conventional oil. The difference is, the additives dont start breaking down in the synthetic as fast as the conventional (in addition to there being less of them to break down), so the work the oil does at cleaning, isn't erased as quickly with the synthetic as it its with the conventional oil. If you change your oil and filter whenever it starts to get dark, then you should see no difference in buildup between conventional and synthetic. It's just, with conventional, this becomes so frequent that nobody ever really keeps up on it. Synthetic gives you much more of a wider bearth.

It's much more of a prevention of deposits from forming and a lack of material for the deposits to form that makes synthetic a cleaner oil than by any increased detergent power in the synthetic oil. It's the lack of all the crap that isn't oil that makes synthetic this way, not the presence of a cleanser not found in conventional oil. The same cleansers are in both if they're in it at all.

edit: synthetic basically allows people to do maintenance on their car between the periods of time where the oil starts breaking down and forming heavy deposits. With conventional, this is too frequent for most people to stay on top of, so they get buildup. With synthetic, most people can make it to an oil change between 6000-10,000 miles. If you make your oil change intervals longer than what synthetic lasts for, like every 14,000 miles then you'll have the same level of buildup and sludge that you see in conventional, and the next time you do your oil change in a little over a year, you'll see even more sludge and buildup, just like most people see in engines where they didn't change their conventional every < 3000 miles.

I'm arguing that the cleaning you see is nothing more in synthetic than conventional, you just have a better chance of maintaining and decreasing buildup with synthetic because conventional oil requires frequent changes that most people dont stay on top of. And sudden leaks and gasket failures people find after moving to synthetic that they never had between various conventional oils likely has to do with how synthetic wont thicken at low temperatures (lower than the ratings) like conventional, nor will it start to burn until much higher temps than conventional. So it has a better chance at flowing in places the old oil simply couldn't get to in liquid form. Once it does this, it frees up old buildup since it is by nature, a lubricant, and now you have a bigger leak.

SSC

First off lets loose the chain parts store employee opinion. I know 5 people that work at part stores that actualy know thier head from thier ****. Thats only becasue they have been in it for a long time. I would never ask thier opinion on a mechanical question, thier job is to look up parts you ask them for thats it. If they knew jack about cars they would be getting 3 times as much actually working on them rather then selling parts.

Listen to 57, he knows his stuff when it comes to oil especially synthetic.
As far as this 200K engine being switched over now thier isnt really a reason to do so! IMO its made it this long just ride it out on the dino juice until its time for a rebuild or replacement then start fresh. If you wanted to switch over now do it slowly like 57 mentioned. This will slowly clean the gunk in the engine rather then break it free all at one time. Of course you could just pop a valve cover off grab a flash light and do some inspecting. If the engine has had regular oil changes it just might not have any crap built up in it to worry about.

five7kid

iTrader: (14)

Not true. It's breaking the bonds of the sludge and varnish, not the oil.

What you buy into doesn't change facts. The synthetic base oil itself doesn't break down as readily in synthetics as it does in petroleum based oils. The synthetic base itself is a better lubricant than the petroleum base. The synthetic base itself requires less and fewer additives than petroleum to meet the lubricating requirements. The synthetic base itself is a better detergent (different than a solvent) than petroleum. Some additives, particularly the viscosity index improver, are of themselves not lubricants and tend to be more susceptible to oxidation and breakdown, forming sludge in the process. A Group IV synthetic is superior in every way to a petroleum-based oil.

Simply not true. It is true that synthetics prevent the formation of deposits, but they are truly better detergents as well.

I change my vehicles at one year or 25k miles, whichever comes first. They do not have deposit build-ups AT ALL! But, I use AMSOIL, and only they will stand by their extended interval claims.

Again, you are wrong. You keep saying the same things, I keep saying you're wrong and why, and you repeat what you said as if saying it again will prove it is right. You are simply wrong. You don't understand the chemistry.

I don't buy into the "synthetic causes leaks" either, as I've already said. In the early days (like 30 years ago), Mobil 1 did tend to leak and consume more than conventional oil or AMSOIL. The Rutan Voyager around-the-world-no-stop-no-refuel flight got Mobil 1 to sponsor them (read: give them money) and they used their product. Their engines consumed more oil than they anticipated, and if they hadn't had more on board they could pump into the engines, they wouldn't have made it. Mobil finally addressed the issue in the 90's. Another anecdote: I had a high school classmate whose family owned a Mobil gas station. In the early 80's, he bought a new Suburban and switched it over to Mobil 1 at about 10k miles. He got tired of the leaks and consumption and switched it over to AMSOIL - no more problem.

As for switching over a 200k miles engine: As I related in an unrelated thread, the 305 I pulled out of Berlinetta #2 had 304k miles on it (probably more, because the speedometer was slow). Original engine, never rebuilt. Although not as clean as my engines, deposits were reasonably low. Wear was minimal. I wouldn't have hesitated to flush and switch that engine over to synthetic if I was going to keep running it. We'll never know, though, because the engine has gone to car heaven now (after another TGO member got the heads).

safemode

iTrader: (1)

You haven't said anything to show or prove how the detergents in synthetic are better than the detergents in any decent conventional oil, you just state how synthetic's abilities combine to yield less deposits and sludge. That's why my argument hasn't changed. Everything you repeated after saying i was wrong was exactly what i said, just rehashed. The benefits and superiority of synthetic isn't being contested in any lubrication or longevity manner. It's in pure detergent ability. In that respect, i've not seen any studies or tests that show an initial change in synthetic affected deposits in an engine in the first 3000 miles any different than an initial change with any new decent oil.

What i'm saying is that the percieved superior detergent ability of synthetics is due to all of their inherent abilities at being better lubricators and having less additives rather than some property of a detergent that doesn't exist in conventional oil. And that the effect of this is not seen in as little as 3000 miles, but takes many complete oil changes (or at least filter changes) to have a noticable effect.

You've not said anything that counters that. What i'm contesting is the idea that the first oil change using synthetic is any different than switching to a non-crappy conventional and maintaining the oil change frequency the engine demands. You're stating that it does and I've not seen anything that suggests this is so anywhere that extensive long term (or even semi-long term) synthetic oil tests have been done.

91_RED_Z28

Ok well now that i have received like 20 different answers...so i should probably stay with conventional oil, and drop down to 10w-30? I just want to be able to use all Lucas Oil, since that is what just about everything is in my car except fo rmy motor oil, because they only make synthetic motor oil...that is the only reason why i asked...but from everyones opinion should i stick with convetional? if so what type and weight? or should i go to synthetic and again if so what kind and type?

five7kid

iTrader: (14)

Perhaps you should just ask Lucas Oil what they suggest. Opinions don't seem to be worth much.

Viprklr

iTrader: (5)

How's this for an answer:

You don't need to. If you feel that you must switch to synth, then just do it slowly as five7 and I suggested.

91_RED_Z28

ok...thank you...i do appreciate the help...