Agreed. Red Line is a very good brand of oil. If you guys would just do a little research, you would see that 75W90-NS is the correct oil to use in the WRX's manual transmission and 70W-90 is the correct oil to use in the WRX's rear differential. I have been very satisfied using this exact combination in my own car for 18,000 miles now.
This information is taken directly from Red Line's website (
www.redlineoil.com):
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Synthetic Gear Oils
Designed to provide the highest degree of protection and greatest efficiency for your drivetrain. Red Line provides a complete line of drivetrain lubricants which are optimized for differential, transmission, or transaxle use over a wide range of temperatures. Proper selection depends upon the manufacturers' requirements and whether the application is for passenger automotive, commercial, or racing use. Red Line Gear Oils contain polyol ester basestocks to provide excellent lubrication even under extreme conditions of high-loading and high-temperatures--their natural lubricity provide excellent slipperiness which reduces the sliding friction in hypoid gears to reduce wear and temperatures. The synthetic basestocks have a natural multigrade property, so large amounts of unstable thickeners are not required to manufacture our gear oils, which means that Red Line Gear Oils will provide a stable viscosity for even extended periods of use. Red Line also manufactures gear oils which can be used in limited-slip differentials without the use of additional friction modifiers.
75W90 NS
This GL-5-type gear oil doesn't contain the friction modifiers for limited-slip hypoid differentials. This makes the transmission synchronizers come to equal speeds more quickly, allowing faster shifting and much easier low-temperature shifting. Can also be used in racing limited-slip differentials where weak spring design causes too much wheel spin.
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This information was actually already referenced in Post #15 of this thread by jwtarbaj. I'm just re-posting it to emphasize that Red Line (among others) is a quality brand of oil that is suitable for use in our cars.