Synthetic High Mileage - old vehicle - leaks?

[OceanRuns]

My understanding based on what I have read is synthetics don't 'cause' leaks. But, they can remove gunk, thus exposing leaks. And, they can flow faster out of existing leaks.

Does using synthetic high-mileage oil (like Mobil 1) counteract this with its seal swelling properties? Or, is it still a risky proposition that might result in more oil on the ground.

My question is primarily in regard to 30-40 year old vehicles. Assume some leaks already, and most likely never any synthetic used.

 

[jdavis]

I don't really see the point in using Syn in a 30-40 year old vehicle that's never had/needed it..

 

[ThirdeYe]

My 99 Firebird leaked when I bought it. Mobil 1 high mileage did nothing for the leaks, but it also did not make them any worse. I had better results with Pennzoil high mileage in terms of stopping the leak. In fact, it stopped it completely.

 

[zray]

Originally Posted By: jdavis
I don't really see the point in using Syn in a 30-40 year old vehicle that's never had/needed it..


Wow. Are you some kind of new car snob ? Just because an engine has never had a synthetic oil change certainly does not mean it doesn't need it.

Jeez.

Every engine can make use of a quality synthetic oil. In fact, old cars probably need it more than the new ones. Without modern fuel injection vintage cars are likely to be running a A/F ratio that is not optimal, a prime candidate for accelerated wear. A good synthetic can mitigate some of this wear much more effectively than a conventional oil.

Z

 

[fmia]

If it leaks use high mileage. Maxlife works, supertech works, lots of dudes like mobile 1 high mileage(I've never used it so I don't know) quaker state has a high zink high mileage oil with gteat all around add pack it works great in my moms Windstar. Pennzoils high mileage add pack looks awesome like pyb. All kinds of molly if that flips your trigger. I think max life and quake state HM did the best in the Windstar even tried smittys HM from lmart. They often mark ot down to $9 a 5qt jug but it turns real dark real quick bit seemed to stop leaking. But yes seal swell and one grade or so higher than it used while young helps. All oils these days clean well so its not a synthetic thing anymore that will find your leaks for ya.

 

[Ramblejam]

Originally Posted By: zray
Without modern fuel injection vintage cars are likely to be running a A/F ratio that is not optimal, a prime candidate for accelerated wear. A good synthetic can mitigate some of this wear much more effectively than a conventional oil.


You may want to clarify your position in more detail (hint: properties of PAO/POE as it relates to performance under fuel dilution).

 

[Triple_Se7en]

I believe Pennzoil High Mileage relieves the most issues.

 

[lairdwd]

Originally Posted By: jdavis
I don't really see the point in using Syn in a 30-40 year old vehicle that's never had/needed it..


Sometimes you get rebates on synthetic and get it free. Topic is on-point and I have same question.

 

[gregk24]

Synthetic is better at cleaning than conventional. Im ok with that, in a healthy engine not a whole lot should be built up anyway. If its a nasty engine maybe a synthetic blend would be a good choice.

 

[Clevy]

Originally Posted By: gregk24
Synthetic is better at cleaning than conventional. Im ok with that, in a healthy engine not a whole lot should be built up anyway. If its a nasty engine maybe a synthetic blend would be a good choice.



Actually no it's not. Where syns are better is they leave less deposits behind. So a conventional cleans up then leaves deposits,whereas a syn cleans up and leaves nothing behind.

 

[Clevy]

Originally Posted By: zray
Originally Posted By: jdavis
I don't really see the point in using Syn in a 30-40 year old vehicle that's never had/needed it..


Wow. Are you some kind of new car snob ? Just because an engine has never had a synthetic oil change certainly does not mean it doesn't need it.

Jeez.

Every engine can make use of a quality synthetic oil. In fact, old cars probably need it more than the new ones. Without modern fuel injection vintage cars are likely to be running a A/F ratio that is not optimal, a prime candidate for accelerated wear. A good synthetic can mitigate some of this wear much more effectively than a conventional oil.

Z


A properly jetted carb isn't much worse than fuel injection. More wear is a dream.
As we've seen via used oil analysis wear rarely increases as fuel dilution increases. They aren't linear.
And conventional oils aren't any worse when it comes to wear control. In fact there is a strong case that wear s controlled better using conventional oils,they just don't last as long in service.
Wives tales

 

[Ramblejam]

Originally Posted By: Clevy
Actually no it's not. Where syns are better is they leave less deposits behind. So a conventional cleans up then leaves deposits,whereas a syn cleans up and leaves nothing behind.


Originally Posted By: Clevy
And conventional oils aren't any worse when it comes to wear control


So there's zero variance between differing base oils in regards to their respective cleaning ability, and performance under excess fuel dilution?

Come on, Clevy -- you should know better than that.

 

[jdavis]

Originally Posted By: zray


Wow. Are you some kind of new car snob ?


Lol I might be becoming one! I've owned plenty of carbed vehicles over the years and would never go back.

 

[zray]

Originally Posted By: Clevy
Originally Posted By: zray
Originally Posted By: jdavis
I don't really see the point in using Syn in a 30-40 year old vehicle that's never had/needed it..


Wow. Are you some kind of new car snob ? Just because an engine has never had a synthetic oil change certainly does not mean it doesn't need it.

Jeez.

Every engine can make use of a quality synthetic oil. In fact, old cars probably need it more than the new ones. Without modern fuel injection vintage cars are likely to be running a A/F ratio that is not optimal, a prime candidate for accelerated wear. A good synthetic can mitigate some of this wear much more effectively than a conventional oil.

Z


A properly jetted carb isn't much worse than fuel injection. More wear is a dream.
As we've seen via used oil analysis wear rarely increases as fuel dilution increases. They aren't linear.
And conventional oils aren't any worse when it comes to wear control. In fact there is a strong case that wear s controlled better using conventional oils,they just don't last as long in service.
Wives tales


Just call me an old wife then. In my very limited experience of 50 years building engines and abusing them, engine wear can quite easily be divided into 2 catagories; substantial wear when using conventional oil, and negliable wear wean using synthetic oil. And somehow I didn't have to rely on an oil analysis to be able to read a micrometer and see wear firsthand.

Z.

 

[zray]

Originally Posted By: jdavis
Originally Posted By: zray


Wow. Are you some kind of new car snob ?


Lol I might be becoming one! I've owned plenty of carbed vehicles over the years and would never go back.


Ha ha . I don't think that alone can qualify you for snob status. Now if you were working at the checkout lane and refused to sell me synthetic oil because I was going to use it in a 50 year old car, now that would cross the line .

Z

 

[tig1]

I was using M1 5-20 in the seventies in engines calling for 30 and 40 wt oils. I found that my engines of that era performed better with the synthetic VS dino, and that was with 10K OCIs with the syn as opposed to 3K OCIs with dino. Just my experience.

 

[zach1900]

I have yet to see proof that synthetics clean better. In my anecdotal experience oils like pyb seem to clean better.

 

[aquariuscsm]

Originally Posted By: Clevy
In fact there is a strong case that wear s controlled better using conventional oils


I've heard/read this as well from people who tear down and rebuild engines.

 

[jdavis]

Originally Posted By: zach1900
I have yet to see proof that synthetics clean better. In my anecdotal experience oils like pyb seem to clean better.


Doesn't PYB leave a nice golden varnish? I don't know never used it.

 

[zach1900]

Pyb is probably a blend at least. In fact I think most SN rated oils probably have some amount of syn oil base. We're not talking your dad's Pennzoil.