gear oil

[JohnTDI]

Hi all,

Friend of mine is adding some synthetic gear oil (75w140) to his regular motor oil at each
oil change and he says the extra protection from the gear oil is helping his engine too.
Now I'm not an oil specialist but I think he's wrong about this.

what do the specialists on the forum think??

thanks,

John

 

[Patman]

What does he hope to accomplish by doing this? What extra protection does he think he's getting? Why doesn't he just find an oil with a good additive package instead? Tell him to come here for a good education on oils!!

 

[satterfi]

Aren't some of the additives in GL-5 rated gear oils corrosive to some bronze alloys?

I hope all the bronze bits in his engine don't have a problem.

 

[RB Shannon]

My understanding is that EP type additive's are much more agressive than AW type adds becoming active at higher temps at around 200 F.In my opinion he could be doing more harm than good causing corrosive type wear.

 

[widman]

since most gear oils use sulfur/phos additives, and sulfur is wht you try to get OUT of base oils because it rapidly degrades them, he deffinitely is doing harm to the oil and it's properties. If he puts enough in that it chemically binds to the cylinders, rings, or bearings, he could have serious problems. The bearings would probably be the first to show serious pitting and wear.

 

[MolaKule]

A harmful and destructive situation.

EP Gear Lubes may have sulfur, phosphorus, and chlorine additves that can form acids and attack copper-based metal alloys such as bearings.

Gear Lubes do not usually attain the same temperatures that do engines oils. Engine temps in certain parts of the engine will create acids from the above mentioned chemicals much faster than they would in a properly functioning differential, for example.

 

[JohnTDI]

patman:
He was hoping that the ep additives were helping in the engine as they did for the gear.

all:
thanks for the information, I wil print this out and give him a copy; and refer him to this forum too. Maybe he might learn something from it.

tnx all!!
John

 

[widman]

I'll add one more reason: Gear Oils use acidic additives. Engine oils use Alcaline additives. Here is a quote from a Chevron Caution Buletin:
"Some oils are incompatible due to differences in
additive chemistry. If these oils are mixed, insoluble
material may form and deposit in the oil system. There
have been cases when grease-like substances plugged
lines and filters in circulating systems resulting in
equipment shutdown. Analysis of these substances
showed they were derived from oil additives.
Incompatibility can exist between two Chevron
products or between a Chevron product and a
competitive product. In some cases, two unused oils
may test as being compatible (such as in the case
when a new oil is being compared to the competing oil
that it will replace) but incompatibilities can arise when
mixing the new, unused oil with the used competitive
oil.
Cause of Incompatibility
In rare cases, an adverse reaction may occur between
two oils at high temperatures or pressures. Most often,
however, the cause of incompatibility is the
neutralization of an acidic additive in one oil by an
alkaline additive in the other oil. The reaction occurs in
the presence of water. A soap (usually a calcium soap)
precipitates as a grease-like gel which can interfere
with lubrication and oil flow.
Other factors besides acid/base chemistry such as
metals, viscosity, color, emulsifiers, tackifiers and the
age or cleanliness of the fluid may also affect product
compatibility.
Small amounts of the alkaline-type compounding from
the oils in List B mixed with the oils containing acidic
components in List A can:
1. Cause stable emulsions to form when water
contamination occurs.
2. Cause reaction between compounds to form
grease-like, oil-insoluble deposits that may block
filters and small oil passages."