Synthetic oils have more detergents than conventional oils
If sludge and junk is what's holding the engine together and keeping it from leaking, then that better oil WILL clean out the gunk.
It won't CAUSE leaks, it'll just show you where leaks have always been likely to be, just blocked up with gunk

Yep, nothing a little cat litter on the driveway/garage floor won't address.
I'm not a mechanic, but it seems that if oil/fluid leaks are a real issue that a rebuild should be considered. Of course, that's probably like plumbing where you fix one thing and something else springs an even greater leak than you had.

My DD is a 2013 Tundra with 270K on it.  I'm the original owner and have only used Mobil One since I bought it.  

Never had an oil leak.

YMMV

This. If it's not a puddle, it's not really a leak. Spots on the driveway are just a minor annoyance. A real truck should have enough mud or dirt falling off of it from time-to-time that the spots resolve without further attention, anyway.

Old wives tale.  Full synthetic will help your engine last far longer than conventional.   I have been using synthetic in my cats for the past 30 years and not one of them has ever leaked.

It's an old wives tale from the early 80's.
In 1981 I used Mobil 1 on my 1976 FIAT, and tt leaked at the oil pan a little because that gasket was not as tight as the others, and it was cork.
All of the gasket materials and machined surfaces are so much better now, that it's not an issue anymore.

Don't forget to rotate tires too.

This.

Many of the conventional dino oils use the seal swelling additive. Several of the non-high mileage synthetics, don’t.

Switching to the ones without the seal swelling additive, can expose leaks from old gaskets.

See my previous post.

The problem occurs mostly when someone’s used conventional dino oils for a long time, THEN switches to a non-high mileage synthetic.

Using a synthetic from Day 1 (even the non-high mileage variants) isn’t an issue (and can have benefits for engine longevity, depending on driving).

The sludge/clean out theory, while it has some potential merit, isn’t what I’d think is the most common cause.

Been a car/track nut for decades, including being in communities and forums where nuts regularly send in their oil samples for UOA (Used Oil Analysis) at places like Blackstone labs.

Have known some folks with older vehicles, who’ve been doing UOAs on dino with clean reports, then decided to switch to synthetics. UOAs didn’t show any signs of increased sludge/cleaning (which would show up in the used oil), but the vehicles developed slow leaks.

The solution was to either replace all the old seals and gaskets, or switch to a high mileage synthetic with seal swelling additives, or back to the dino they’d been using (which likely also had a seal swelling additive).

Ah, the change by attrition strategy

Fix your oil leaks so they don’t become bigger oil leaks. Somehow people blame oil instead of their neglectful ownership for leaks.

No they don’t.

lol.

Lol

Try Mobil 1 High Mileage.

From my understanding a traditional oil has many smaller particles and synthetic is more consistent particles size.  So a traditional oil should leak before a synthetic would as it thins out more than synthetic will.  

Sound like some bullshit to me.  Old cars just get leaks and need gaskets sometimes.  None of my cars have had suspicious leaks with synthetic and I doubt whoever owned them before me used it.

I’ll clarify this.





Conventional PAO VS M-PAO for reference.  It has nothing to do with the molecular size. At all.


There is a test called the Noack volatility test. It’s how much of your oil is lost into vapor at 250c for 60 minutes.

A Dexos 1 Gen 3 cannot lose more than 13% of its mass.  A normal GF6 SP rated is 15%

Yes. Your oil will naturally have some volume loss.  Because the refining process isn’t clean. So it still has some light ends in it. Once heated up, a Group 2 base oil will lose more than a group 3.  In theory a group 3 will lose more than a Group 4. (GTL base stocks are/can be the exceptions.)

Hey this isn't nuclear physics

Correct.

I’m a fucking idiot.


I just got the oil flavored autism.


MrHiggs is the true genius.

Hats off to you and anyone else who has the intelligence and interest enough to take the time and put in the effort to really learn and understand things like this. Me I'm just a wrench turner who can follow mfg recommendations. When it comes to graphs and formulas , chemical analysis and shit like that my eyes glaze over and I start thinking about lunch.  

I see.   While I got you here.    I'm doing my first Honda engine rebuild.  Usually I trade mechanics for paintwork but I want to do this one myself.  B20 4 cylinder.  Do I need to use break in oil or can I just start it on full synthetic day one?   Gonna be all new parts and machined out a little for new pistons. Whats the difference with a break in oil?

Break in oil - no.

Change the oil after a few hours, yes.


Manual rebuilds will have assembly lubricant involved.  So you’ll want to get that out.  As it’s all going to end up in your filter anyways.

NO.

Attached File

I rebuild ATV engines fairly frequently.   I have always used Rotella T4 for initial run, then switched to T6 after break in (100 miles).   Was told by several engine builders that syn is "too slick" to allow rings to seat properly.

I can tell the full syn runs quieter and cooler than the T4 (fan doesn't kick on nearly as often running the T6).

Too slick isn’t a thing.


Like… it’s just not a thing.   I can’t even explain it besides someone’s mouth opened up and shit came out.

Okay instead of an extensive edit. I’m going to make this post.  Let me dig back into the archives.




So a lubricant lowers friction. This is true for all lubricants. Picking the proper viscosity grade is key to determining your friction. As, too thick will make more friction. And too thin will make more friction and wear.




This is your different types of lubrication regiments.


As you can see, touching / sometimes touching / never touching.

Most of the time you want to stay between mixed and hydrodynamic.  The problem with mixed, is particulate contamination.  If I had my books with me I’d have more pictures. But here’s something I found:



If your oil film is too thin, and your particulate contaminants is larger than your fluid film gap,  then you will start seeing abrasive wear.

If your fluid film gap is too thin, you can see either mirroring, like this:



This engine has 1.2 million miles on it before we opened it up.  The cross hatching on the sleeves was completely mirrored over.

Or on the bearing you will start seeing pitting from the viscosity loss, and the oil literally getting turned to stone from the pressure:



Thus the pitting. Those bearings should have looked like this:



Worn, mirrored but not pitted.  (These are the bearings out of the 1.2m mile engine.  The other ones were out of a Cummins 5.9 that had spun the bearings due to maintenance plan issues.)

They sorta work like this:  



On your major bearing parts, the oil actually forms a film. Typically has 3 layers inside of this film.  One against the bearing, one against the shaft, one layer in the middle. Due to the differences in surface tension.  This is how fluid friction works.


None of this, has anything to do with being “too slick” and breaking in engine rings.  If anything the rings “don’t break in” because there’s less carbon development around them from the blow by burning off. Which… is a good thing.  

But anyone who uses “too slick” to describe full synthetic oil… like I’ll talk to, and try to help them understand. But chances are I’d be better off telling my cat about full synthetic 5w30’s advantages over a 10w30.


Sorry for getting way too technical about this lubricant, I've got a touch of viscoustism.

Of course! It's GD so have to try to wait till pg 2

lol they might come less often if you throw their stuff into the trash can while they are still there

Everyone has their nerd garden, at least yours is educational

Mine uh… pays bills. And I make pretty good money off it. Not saying I’m the most wealthy person on this forum - I know I’m not.  But, I’m not hurting yet.


The least I can do is share info that is other wise hard to get. As a lot of the stuff I talk about isn’t really Google-able.

Sure, all the old carbon and gunk could get cleaned out and the hole that was already there could start leaking.

It's like if your teeth were held in by tartar and you cleaned it all off.

I figure it is the same idea as not changing tranny fluid if you haven't done it in 100k+ miles. If your transmission is on the verge of failure, then changing the fluid may kill it since the disintegrated clutch material is floating in the burned out fluid is the only thing making it work. But if it is in good shape, changing fluid will keep it healthy.

I like this info. Thank you.

It does remind me of school though! It's fun to get me geek on after chasing imaginary problems for people all day.

Question, best way to get rid of lifter noise on startup. They rattle for a moment. Pretty sure they are bleeding down as the truck sits. If I have to replace them, so be it. Using 10w-30 Castrol Edge synthetic. Same weight as factory recommended.

Car makes a similar but I think it's air in the injectors as it didn't do that if I let the fuel pump prime for night. Lifters are a known thing in the truck.

Go to a 5w30 or 0w30 with a higher moly content.  

Lifters will tap until the oil film forms at the proper viscosity.  An XXw30 is the same viscosity at 100c / 212f. Whether it’s 0w30 or 10w30.

Faster the oil flows = the better film barrier you will get faster = less tapping.  To really over simplify it.  

Moly because it tends to stick around after the oil drops down on shut off.  And forms a bit of a barrier like ZDDP does.

Tapping doesn’t mean much. Because you have your antiwear already built up on the part.




So that’s built up on the microscopic level around your parts. And will “wear off” before metal does.

JEEP Inline 6?

Hey I appreciate that you throw the knowledge out, I've learned up a few things along the way. Watching the the occasional smack down is pretty entertaining as well