Another synthetic oil question - heard a conflicting comment

[MikeyM]

Hi all,

Stock '69 383HP engine, 64k original miles. Today, a neighbor dude who has been doing restorations for quite some time stopped by while I was doing an oil chance. He asked me if I was using zinc additive and told me not to use synthetic because the engine is not clearanced for it. He says he wiped the bearings on 2 engines using it. Now he has me worried so I wanted to ask for your input.

I'm aware of the whole zinc thing for flat tappet cams and I have used Mobil 1 15w-50 in our VW bus for years since the break-in and also this Bee for the last 2 oil changes and have put at least 2-3k on it. Mobil 1 15w-50 has over 1200ppm Zinc/phosphate... I think maybe even 1500 which is why I use it. I know tons of people who use Amsoil Z-Rod as well as others who use synthetic with no issue. For older cars I have never heard of what he speaks. Can I please get some input on this? I just finished an oil change for a trip up to Sac tomorrow and really don't want to change it but I will if I should.

Thanks much,
Mikey

 

[RemCharger]

I'm with neighbor dude.

 

[MikeyM]

Damn. why is that, might I ask? He said it's probably ok to drive around for a week or 2 but best to change it out. This kind of blows me away. I mean... isn't there a heck of a lot more to it than "you'll wipe your engine if you use syn"??

 

[Kern Dog]

"Not clearanced" for it ???

 

[MikeyM]

KD, that's the first thought that came to my mind, too. He said it's too thin. Not enough bearing cushion, if you will. The synthetic oil manufacturers engineer their oil for bearing clearances of most cars from like the 50s up to around the 80s/90s I would guess... then all the 0W stuff started coming out.

 

[RemCharger]

Oh those synthetic oil marketers .......

 

[Strato58]

Every one of these oil threads brings me back to the 540 rat blog which poo poo's the entire super high zinc idea.

 

[Kern Dog]

I don't see how a synthetic oil with the same weight numbers would not work.
A 10 w 30 synthetic would be just as thick as a 10 w 30 conventional oil.

 

[RemCharger]

And conversely i dont see how a conventional oil that always worked, won't work.

 

[Strato58]

Nobody has an answer why. Most of it appears to be folklore.

 

[69Bee]

You don't mention if you are using racing oil or not, so I looked up Mobil 1 15W-50 synthetic oil and nowhere on their website or on the oil spec sheet does it mention any zinc & phosphorous is in the oil. Personally, if you are not using a roller cam, I wouldn't be using a synthetic oil. A roller cam/lifter needs a slippery oil for the rollers and cam lobes which is the purpose of synthetic oil. A flat tappet cam/lifter is a wiping action and requires a regular EP SAE oil of the appropriate viscosity with the Zn and Ph already in it. As far as your neighbor stating it is too thin, that is why you choose the proper viscosity you desire. The synthetic oil does not have a negative impact on the bearings, only roller vs. flat tappet cams. My opinion is he did not build his motors correctly and that is the reason he lost the bearings.

Mobil 1™ 15W-50 | Mobil™ Motor Oils

 

[Kern Dog]

I know some people that swear by synthetic stuff. I'm talking guys that don't work on their own stuff, these are dudes that believe what they are told.
They may be right but for my cars, all I use is conventional stuff.

 

[R413]

Maybe his 2 engines were ready to schuck anyway?

Do not use 0 weight oil in an old car. Lots of stock and SS racers use it for heads ups, and most say it causes engine damage.

I know plenty of guys using synthetic in old cars, use a thicker one, not 0-20. I'll stick with conventional oil. Joe Gibbs Driven, VR-1 etc.

I'm not on board with the "all old cars need 20/50" either.

 

[slepr1]

Easy to just use the conventional oil. Why use the synthetic oil if not necessary. You aren't doing any better with synthetic so why use it? On daily drivers, yes synthetic

 

[MikeyM]

Good points, thanks.

R413 - right, that's why I went with the 15w-50 in addition to the ZDDP levels.

Slepr - I usually drive my car every day. Usually about 10-20 miles, sometimes 60 just depends.

69Bee - here's the link to Mobil 1's website. On the right in blue is a link to a pdf with their zinc levels. It says the standard 15W-50 has 1320ppm. And I'm kinda with you on his bearing issue.

Rem - the main reason I like synthetics is the temperature threshold. It seems to be far higher than conventional oils unless I'm missing something.

And sorry guys, i didn't mean to start up another this vs. that oil thread but I'm just not understanding that if the syn oil is the same weight as conventional, has a good enough ZDDP level, the rating exceeds SE and SF specs, is slipperier, and has a higher temp threshold, what is not good about using it? Not trying to be a smartass, just trying to understand.

Honestly, I have no issue with conventional oil except the "breakdown" temperature point which is the main reason i went to syn oil. This engine sees sustained speeds of 70 -75 on the highway @ 3k + rpms (sometimes more if a German car f&*cks with me) and i just want to use what will keep it alive and lasting. And I've used VR1 in the past a few times and liked it. If it will provide the same level of thermal protection and lubrication that syn oil does, heck, I'm on board.

Thanks,
Mikey

 

[coloradodave]

I have used Mobil 1 Full Synthetic for over 30 years. First in my sport bikes, and when I discovered how clean the inside of the engines stayed, I started using it in my street/strip cars. I've never had a bearing failure on any of my engines, including my stock Jeep Cherokee V-6. As they say, opinions are like *ssholes; Everybody has one!

 

[Kern Dog]

As they say, opinions are like *ssholes; Everybody has one!

 

[68-500]

Basically synthetic means the oil molecules are more uniformly sized. I doubt like hell your engine cares whether you use 15w-50 synthetic or 20w-50 conventional. Unless you’re regularly starting it below 32*. Zinic and all that is great, but oil film strength is what matters. Once you lose your oil film and you’re to the point of relying on the zdp package to save your engine your in trouble. Leave the 15w-50 in it. And never use additives in the oil you’re just diluting the chemistry that it was designed with.

 

[turbine68rt]

Nothing wrong with Mobil1 15w-50 for flat tappets in the latest SP version. Zinc is about 1100ppm with less detergents (key factor). I've been using it exclusively for several seasons. Before that it was VR1 but the 20w50 was a little too heavy.

 

[Dennis H]

Whole Planet (mostly) uses synthetic. Must be a reason. Amsoil Z Rod 10-30. Synthetic. High Zinc. 440. Purrs for a tired old dog. Annual due to low miles used.