Thank you. I have been feeling uneasy about using Amsoil in all 3 applications. Just didn't feel right. I'm not a mechanic, so that's why I'm asking the guys with experience. I have always liked synthetic for the engine, and everything I've read here supports that. Your recommendatins for the primary and tranny echo those I've seen from others, and I recognize experence and common sense when I see it. I'm not looking for miracle oils or whatnot. Just what works over time and mileage. Thanks for the advice!

 

I dont know zip about oil so I got this From an article on Baker Transmissions. Its kinda long winded.

Modern oils are complicated, and transmission oils are no ex-
ception. Gear lubes carry a GL rating, which defines how much
pressure (load between gears) they can withstand. The most com-
mon ratings today are GL-1 and GL-5.
GL-1 lubes have a much lower pressure rating than GL-5 oils.
Gear lubes come in many viscosities (weights), with the most com-
mon being 75w90, 75w140, and 85w140. Imagine these oil poly-
mer molecules looking like a spider… when the oil is cold the spider’s
legs contract (like a dead spider), which lets the polymers bounce off
each other, creating easier flow. Flow in oil is measured as viscosity,
so when the oil is cold the viscosity is lighter (the 75 part of
75w140). As temperature increases, the spider’s legs open up and
connect with the “legs” of other polymer molecules, making the oil
thicker and increasing viscosity. This is how oil can change weight
from 75 to 140 with a change in temperature. When oils are
sheared with miles of use, the “legs” are cut off, preventing the poly-
mer molecules from linking to-
gether and making the oil un-
able to change viscosity.
Besides pressure ratings,
chemistry is different be-
tween GL ratings, and nor-
mally they don’t interchange.
Most GL-5 rated lubes are
not compatible with GL-1 ap-
plications because GL-5 oils
contain high pressure addi-
tives that attack “bright met-
als” such as copper, brass,
and bronze that can be found
in some transmissions. Oils
such as Spectro 6 Speed
contain special buffers that
allow this GL-5 rated oil to be
used in GL-1 applications
without fear of bright metal
damage. GL-1 oils should
never be used in GL-5 appli-
cations. They won’t cause
any physical damage to met-
als but they also won’t stand up to the intense pressure found in a
GL-5 environment.
Syn3 is nothing more than 20w50 synthetic motor oil. It will work
in a transmission if there is nothing else available but there’s no good
reason to use it when there are better choices. Motor oils are de-
signed to lubricate motors, not transmissions, and they have totally
different chemistry. Gear lubes use generous amounts of Zinc
(zddp), phosphorus, and other extreme pressure anti wear additives
not found in motor oils. They don’t need much in the way of deter-
gents (no fuel, carbon or ash contamination in transmissions).
So if you don’t want the gear teeth in your transmission to turn
blue, gold, and purple, do the following:
Keep your transmission filled with a quality GL-5
rated oil and change it every 5000
miles or once a year to keep fresh
legs on the spiders.