The Copper Strip Tarnish Test (ASTM D130-10) is a standard test of a lubricant to indicate how corrosive it is to copper alloys that may be in a transmission.
My restored 1989 Suzuki Sidekick has brass synchromesh transmission components that may be vulnerable to additives found in many GL5 lubricants. As a result, my owner's manual specifies a GL4 75W-90 or a GL4 80W-90 lubricant for the manual transmission and transfer case.
Lubricants that are "yellow metal friendly" are hard to find. I perused through data sheets and called lubricant manufacturers to find copper strip tarnish test results for their products. Those lubricants that I found test results for are in the table below.
Code:
M/T FLUID & GEAR OIL SAE API CLASSIFICATION
Amsoil Long Life FGR 75W-90 GL5 1B Dark Orange
Amsoil Severe Gr SVG 75W-90 GL5 1B Dark Orange
Amsoil M/T Fluid MTF 5W-30 1A Light Orange
Amsoil MT & Gear MTG 75W-90 GL4 1B Dark Orange
Citgo Citgear Std XD 75W-90 GL4 1B Dark Orange
Delo Gear Lubric ESI 80W-90 GL5 2A Claret Red
Delo Trans Fluid ESI 50W 2A Claret Red
Red Line MT-90 75W-90 GL4 1A Light Orange
Red Line NS Gear Oil 75W-90 GL5 1B Dark Orange
Red Line 75W90 GL-5 75W-90 GL5 1B Dark Orange
A brief description of the test can be found here: description D-130. The classification scale ranges from 1A (least corrosive) to 4C (most corrosive).
My restored 1989 Suzuki Sidekick has brass synchromesh transmission components that may be vulnerable to additives found in many GL5 lubricants. As a result, my owner's manual specifies a GL4 75W-90 or a GL4 80W-90 lubricant for the manual transmission and transfer case.
Lubricants that are "yellow metal friendly" are hard to find. I perused through data sheets and called lubricant manufacturers to find copper strip tarnish test results for their products. Those lubricants that I found test results for are in the table below.
Code:
M/T FLUID & GEAR OIL SAE API CLASSIFICATION
Amsoil Long Life FGR 75W-90 GL5 1B Dark Orange
Amsoil Severe Gr SVG 75W-90 GL5 1B Dark Orange
Amsoil M/T Fluid MTF 5W-30 1A Light Orange
Amsoil MT & Gear MTG 75W-90 GL4 1B Dark Orange
Citgo Citgear Std XD 75W-90 GL4 1B Dark Orange
Delo Gear Lubric ESI 80W-90 GL5 2A Claret Red
Delo Trans Fluid ESI 50W 2A Claret Red
Red Line MT-90 75W-90 GL4 1A Light Orange
Red Line NS Gear Oil 75W-90 GL5 1B Dark Orange
Red Line 75W90 GL-5 75W-90 GL5 1B Dark Orange
A brief description of the test can be found here: description D-130. The classification scale ranges from 1A (least corrosive) to 4C (most corrosive).