IMPROVES SHIFTINGRed Line MTL and MT-90 are able to improve shifting inmost manual transmissions and transaxles.
Theyprovide a relatively constant viscosity as temperaturechanges and provides the proper coefficient of friction toallow synchronizer engagement. Most gear oils are very

40,000Viscosity@32°F

Viscosity@0°F
30,000

10W30 Motor Oil

ATF

ATF

80W Gear Oil

20,00080W Gear Oil

080W90 Gear Oil

1000

Red Line MTL

2000

80W90 Gear Oil

10W30 Motor Oil

3000

10,000

0The time this process takes depends on how easily thesynchro ring moves and the rate of frictional energy
transfer between the two synchronizer surfaces. Higherviscosity lubricants slow the sliding of the synchro ring on
the input shaft and require a longer time for the oil to besqueezed out from between the mating synchronizer
surfaces. After the lubricant is squeezed out, thecoefficient of friction of the lubricant determines the rateof frictional energy transfer between the two surfaces.
Slippery lubricants such as hypoid gear oils can take toolong to synchronize the gears, which promotes
synchronizer wear. Red Line MTL and MT-90 has acoefficient of friction which is greater than conventionaloils, allowing a quicker transfer of frictional energy. Thegraph below
shows the desirable friction curve
demonstrated by Red Line MTL compared toconventional lubricants. Note how the coefficient offriction is greater for the MTL than all others except themotor oil. Some motor oils have an adequate dynamic
coefficient of friction, but most have problems with thestatic and low velocity coefficient of friction which canresult in clashing.
Clashing of the gears (actually clashing of thesynchromesh gears, since the drive gears are always incontact) can occur if excessive shift effort is used inorder to shift the locking ring into place before thesurfaces have achieved equal speed. It may also occur
at the end of a reasonably smooth shift if an instability
exists in the coefficient of friction, causing stick-slip tooccur. In this form of clashing, the ring slides on themating synchro gear, but a sudden slippage causes agrinding of the gears. In order to prevent stick-slip fromoccuring and the gear clashing which results, thecoefficient of friction should inflect downward as therelative speed drops to zero.
0.18

All oils are slippery, and with most lubricatedcomponents, the slipperier the better, but this is not sowith manual transmissions. The synchronization ofshifting gears requires friction to transfer energy from thesynchronizer, which is locked to the input shaft, to its
mating surface attached to the gear to be locked in as
the drive gear. Few modern transmissions use sliding
gears to change gearing other than for reverse gearing.
Synchromesh transmissions have the gear pairs constantly in mesh. The drive gear is selected by using theshift forks to slide a synchronizer ring, which rotates atthe same speed as the input shaft, in contact with theselected drive gear. Once the drive gear is brought tothe same speed as the input shaft, the locking ring on
the synchro assembly is allowed to slide over and lock
into the drive gear.

Red Line MTL
SAE 30 SF Motor Oil
80W GL-5
Dexron II80W GL-1

0.16

0.14

0.12

0.10

MTL

0.08

0.06
1500

1250

1000

750

RPM500250

0Coefficient of Friction, µnotchy shifting• Eliminatesfor manual transmissions and transaxles• Designed
synchronizer coefficient of friction• Perfect
high-speed downshifting• Enables
shifting even when cold
• Excellent• Eliminates gear whine and rattle at high temperatures
gear protection• High-performance
toward synchronizers• Non-corrosive
manual transmissions and transaxles requir• Satisfies
ing motor oils, or GL-1, GL-3, or GL-4 gear oils

4000

Red Line MTL

BENEFIT SUMMARY

Viscosity of common lubricants at 0°C (32°F) is
compared with Red Line MTL in the chart below. Notethat the viscosity of ATF and 10W30 motor oil seems tobe adequate. These lubricants are not well suited fortransmission use because of two factors - shear stability
and improper coefficient of friction - which will be
discussed in more detail later.
At even lower
temperatures such as -17.7°C (0°F), the differences
between conventional lubricants and Red Line MTL areeven more dramatic. At such a temperature many ofthese lubricants would prevent shifting into certain gears,
depending on the design of the transmission.

Viscosity, cP @ -18°C (0°F)

Red Line MTL is classified as a 75W/80W gear lubricantsatisfying the API Service requirements of GL-3 andGL-4. MTL also satisfies motor oil viscosities SAE
5W/10W/30, and the viscosity requirements for ATFs.
MT-90 is a 75W90 GL-4 and also satisfies motor oilviscosities SAE 10W/15W/40. The additive chemistry
used is non-corrosive, so even though they will provide
GL-4 performance, they will not corrode synchros orbushings. Because of its low corrosivity, Red Line MTL
and MT-90 could also be used in transmissions requiring
GL-1 or GL-3 lubricants. Seal compatibility is designed tobe similar to petroleum-based lubricants.

viscous at lower temperatures. This higher viscosity
requires increased shift effort to move the synchronizer
gears with the shift fork and to squeeze the oil frombetween the synchronizer cone and the mating surface
attached to the gear. Without contact of these two
surfaces, the gear speeds will not be synchronized andlocking of the synchromesh gears will not occur.
Excessive viscosity results in a longer time required tosynchronize before locking occurs.

Viscosity, cP @ 0°C (32°F)

RED LINE MTL® and MT-90 are designed to provide
excellent protection and improved shiftability for manualtransmissions and transaxles. MTL and MT-90 havecured the problem of hard shifting in numerous
transmissions which have notoriously difficult shifting.
The secret to their success is two-fold. First, they havethe appropriate coefficient of friction for most manualtransmission synchronizers. Many gear oils, engine oils,and ATFs are too slippery for proper synchroengagement. Secondly, the viscosity characteristics ofMTL and MT-90 allow proper shifting over the entire temperature range which the transmission will experience.
The synthetic base oils used have a very high viscosity
index which provides relatively constant viscosity as
temperature changes. MTL is a low 75W, almost a 70W,
at very low temperatures and a high 80W, nearly an
85W, at elevated temperatures, providing adequate
viscosity to prevent wear and deaden gear noise. MT-90
is a thicker 75W90 version of MTL. The shear stabilityand oxidation stability of these products are excellent,thus the physical characteristics of Red Line MTL andMT-90 will change little with use.

GEAR AND SYNCHRONIZER WEAR PROTECTION
Most manufacturers of manual transmissions andtransaxles recommend an 80W or 90W GL-4 lubricant.
GL-5 gears oils which are required in hypoid differentials
are not used in most synchromesh transmissions
because the chemicals used to provide the extreme
pressure protection can be corrosive to synchronizers,
which are commonly made of brass or bronze. Typically,
the use of a GL-5 lubricant in a synchromeshtransmission will shorten the synchronizer life by one
half. The extreme pressure requirements of spur gears
and helical gears found in transmissions are not nearlyas great as found in rear-wheel drive differentials. A
GL-4 lubricant provides adequate protection for mostmanual transmissions, unless a unique design
consideration requires the extra protection of a GL-5.
The reason that many manufacturers have maderecommendations of motor oils or ATFs is that petroleum
80W gear oils frequently do not shift well at low
temperatures. Motor oils and ATFs are much more fluid
at lower temperatures and they are not corrosive toward
synchros, but they provide very poor gear protection.
These lubricants provide almost no extreme-pressure
protection. In addition, petroleum multigrade motor oilsand ATFs have very poor shear stability. The shearing
action by a manual transmission on thickeners is muchworse than in an engine or automatic transmission.
Within 5,000 miles the thickeners can be renderedineffective and the transmission will be operating on amuch reduced level of protection, as shown in the graphbelow. In hot weather these transmissions will whine
and rattle because of poor vibration dampening andmetal contact. Red Line MTL and MT-90 provide theexcellent gear protection of a GL-4 gear oil in a synthetic
lubricant which spans hot and cold temperatures and will
not shear or oxidize with use.

Viscosity Units, cSt @ 100°C

VISCOSITY LOSS IN TRANSMISSION USE
12New Oil

After 5,000 Miles

1086420MTL80W
Gear Oil

ATF

10W30
Motor Oil

DIRECTIONS FOR USE
Red Line MTL may be used in transmissions which
recommend 75W, 80W, or 85W GL-4 gear oils, or SAE
30 or 5W/10W30 motor oils. If a 90W GL-4 or SAE 40,
10W40, or 15W40 is required, MT-90 may be used. If thetransmission or transaxle requires an SAE 90 GL-5 gearoil, then Red Line 75W90NS or 75W140NS Gear Oil
may be used. In transmissions which recommend Dexron or Mercon fluids we recommend our D4 ATF which isvery similar to the MTL, being a GL-4 Gear Oil also. TheD4 ATF will provide better low-temperature shiftability,
and the MTL would provide better wear protection forracing use. MTL is not designed for use in rear-wheel
drive differentials. Those generally require a GL-5 lubricant such as Red Line 75W90 Gear Oil. It is not necessary to flush the transmission before replacing with MTL.
Remove the drain plug and drain while warm. Seal
compatibility has been designed to be similar to petroleum lubricants, and leakage should be no greater thanany other oil of comparable viscosity. Being formulatedwith extremely stable synthetic basestocks, MTL and
MT-90 will last much longer than conventional petroleum
lubricants. However, we do not recommend extended
drain intervals, since without a filtration system, there is
no way to remove metal shavings other than draining thelubricant. The regular maintenance intervals are also
recommended to insure that the proper level of the fluidis maintained.

RED LINE®

®

MTL

DESIGNED FOR PERFORMANCERed Line Synthetic Oil Corporation is the leader in lubricant and fuel system chemistry. Red Line sets the standards for equipment durability and increased performance. Red Line manufactures a full line of automotive
products which are designed to provide noticeable improvements in performance:
WaterWetter® SuperCoolantDiesel Fuel Catalyst
85 Plus Diesel Additive with Cetane Booster
Fuel System Antifreeze & Water Remover
SI-1 Fuel Injector & Intake Valve Cleaner
SI-2 Injector & Valve Detergent - BMW # 8888 6 900307
Lead SubstituteMotor Oils - 5W30, 10W30, 10W40, 15W50, 20W50
Diesel Engine Oil - 15W40
Race Oils - SAE 5, 10, 20, 30, 40, 50, 60, 70
High-Performance Two-cycle LubricantsGear Oils - SuperLight, LightWeight, 75W90, 75W90NS,
75W140NS, 80W140
ATF - Synthetic Dexron II / Ford Mercon, Racing ATF,
D4 ATF, High-Temp ATF
CV-2 CV-Joint and Wheel Bearing Grease
Assembly Lube
© 1997, 1992, 1988 Red Line Synthetic Oil Corp.

Manual Transmission /Manual Transaxle
Lubricant

TECHNICALINFORMATION
RED LINE SYNTHETIC OIL CORP.
6100 Egret Court
Benicia, CA 94510(707) 745-6100
www.redlineoil.com