I had previously posted a thread concerning the use of synthetic oils. And I appreciate all the replies and info. I noticed a few of the replies mentioned zinc.

I recall that when my son had his 1973 Plymouth Fury engine rebuilt, the rebuilder told him to use diesel oil in the engine because it contained zinc.

This creates several questions - should one use a zinc additive in his oil? Use an oil that already contains zinc? Should you use diesel oil in a gasoline engine? And if so, why? And why the use of zinc anyway? And does older or newer or rebuilt matter?

Don't laugh at my ignorance - I'm trying to learn.
CB3

 

Zinc, also known as ZDDP is zinc dialkyl-dithiophosphate. This is an extreme pressure additive that until recently was in all oil. Thanks to the EPA, manufacturers have removed this additive from modern oil. NEW car engines don't need it, they are all equipped with roller cams.
Older engines with flat tappets (all of "our" engines) have to have this additive. It is critical for the cam and lifters. Without it, even if broke in properly, a new cam and lifters can be wiped out in only a few thousand miles.
Our engines need ZDDP regardless of new, old, rebuilt. It doesn't matter.
Either use an additive or an oil that has zddp in it.
This lifter had only a few thousand miles on it.
BTW Welcome to FTE, lots of good people here.

 

Thanks Mike,

But where does the use of diesel oil come into the picture?

CB3

 

Thanks for the question and thanks for the answer! I was advised to add the zinc additive to my engine oil by my parts supplier for the reason Mike just gave.

 

Diesel rated oil has a higher zinc content, typically in the 1,200-1,400 ppm range.

Gas rated oils are typically 800 ppm and lower (and decreasing every day).

"Racing oils" like Valvoline, Joe Gibbs and Brad Penn (formerly Kendall) are typically 1,500 ppm +

 

Montana is correct. Diesel oils still contain ZDDP. That's why it was recommended.
One thing, a lot of the oils that contain good amounts of ZDDP say they're for engine break in only. That's so the EPA doesn't come down on them.

 

Royal purple i think has high zinc content, but I hear royal purple also has other additives that have been proven to cause more harm than good. I think they are being sued over it too. So imo stay away from Royal Purple! They sponsor all the sunday car shows on tv so people assume it's good stuff. But i've heard a lot of horror stories of people having to dig into freshly rebuilt engines because of using royal purple.

 

Not to jack the topic, but is this still the case with a roller cam setup? When my 460 was rebuilt there was a hydro roller valvetrain put in.


-Jameson

 

Exactly!

GM's EOS (engine oil supplement), basically a high dose ZDDP additive, was yanked from the shelves after the EPA scare, it was recently reintroduced as an "engine assembly lube" as opposed to an oil "additive", to skirt the EPA regulations, it's the very same stuff though.

Lucas also offers up a ZDDP additive that's readily available in most parts stores.

Engine Break-In Oil Additive - TB Zinc Plus : Lucas Oil= - Engine Break-In Oil Additive - TB Zinc Plus

 

You're okay if your running a roller cam. You won't have to worry about zinc.

 

There are lots of oil threads on motorcycle forums. The latest comparison in in a recent BMWMOA issue . You can find actual analysis of oil brands .
I use Rotella T6 synthetic 5w 40 in my 410 . I use Redline in the BMW GS.
If you look you can find a lot of information on these comprehensive studies .

 

It also has to do with the fact TOO MUCH zinc can also wipe out lifters and cam lobes.

Too little zinc and the cam/lifters are toast relatively quickly. Too much and the cam/lifters are toast a few thousand miles later.

Josh

 

Diesel oil is high in ash so it would have to be changed twice as much. I don't know the current figures on any given diesel oils. Diesel oils have taken a big cut in their zinc. Personally wouldn't even consider putting it in a gas engine unless it had an old api rating like CA CB CC.

 

The diesel combustion process produces ash, the oil doesn't contain ash. It's formatted to control soot and ash. LOL

And diesel rated oil averages 1200+ zinc, more than old SH rated gasoline rated oil.

Nobody complained then about wiped lobes and lifters much did they?

Although my personal opinion is the companies that made lifters and cam blanks cheapened out on the surfacing hardening and oil was blamed.

Didn't help the highest quality producer of lifters (Johnson) didn't produce any lifters during the early 2000s.

Josh

 

OK -based on these replies, I think I will start adding a zinc supplement to my oil with each change.

Thanks for all the info - there is a lot to consider.

CB3