Rick's Free Auto Repair Advice

Where to buy 75W-85 Gear Oil?

You don’t have to buy 75W-85 gear oil from the dealer

75W-85 GL-5 gear oil is specified by BMW, Dodge, Ford, Jeep, Mercedes-Benz, Toyota, and Lexus for use in late model differentials and transfer cases. But finding the product at auto parts stores and quick lube places is a challenge, forcing shops and DIYers to buy it from the dealer or use the wrong gear lube, like  75W-90 product. Don’t believe me? Do a google search for 75W-90 gear lube. Here’s what you’ll find:

Mobil 1 Synthetic Gear Lubricant LS 75W-90
Super Tech Full Synthetic Gear Lubricant 75W-90
Lucas Synthetic Gear Lubricant 75W-90
Castrol Syngear 75W-90 Synthetic Gear Oil
Royal Purple Max 75W-90 Synthetic Gear Oil
Valvoline 75W-90 Conventional Gear Oil
Amsoil Severe Gear® 75W-90
Amsoil Synthetic 80W-90 Gear Lube

Think those gear lubes won’t make any difference? Well, lets take a look a the specs:

Red Line 75W85 GL-5 Gear Oil

Viscosity @ 100°C, cSt 12
Viscosity @ 40°C, cSt 68
Viscosity Index 171

Amsoil Severe Gear® 75W-90

Kinematic Viscosity @ 100°C, cSt 16.6
Kinematic Viscosity @ 40°C, cSt 129.7
Viscosity Index 137

Mobil 1 Mobil 1™ Synthetic Gear Lube LS 75W-90

Viscosity @ 100ºC 14.6
Viscosity,@ 40ºC 103
Viscosity Index 146

Castrol Syngear 75W-90 Synthetic Gear Oil

Viscosity at 100C, cSt ASTM D-445 15.0
Viscosity ar 40° C, cSt ASTM D-445 117
Viscosity Index ASTM D-2270 139

Red Line 75W85 GL-5 Gear Oil compared to Amsoil Severe Gear® 75W-90

Red Line 75W85 GL-5 Gear Oil is 37% “thinner” (more viscous) at 40°C and 27% “thinner” at 100°C than Amsoil Severe Gear® 75W-90. Because the Amsoil lubricant is thicker at 100°C it won’t flow as well, will increase friction and lower fuel economy. Overall, Red Line 75W85 GL-5 Gear Oil is more stable over the 40°C-100°C than Amsoil Severe Gear® 75W-90 with a Viscosity Index of 171 compared to Amsoil’s 137

Red Line 75W85 GL-5 Gear Oil compared to Mobil 1™ Synthetic Gear Lube LS 75W-90

Red Line 75W85 GL-5 Gear Oil is 33.9% “thinner” (more viscous) at 40°C and 17.8% “thinner” at 100°C than Mobil 1™ Synthetic Gear Lube LS 75W-90. Because the Mobil 1 lubricant is thicker at 100°C it won’t flow as well, will increase friction and lower fuel economy. Overall, Red Line 75W85 GL-5 Gear Oil is more stable over the 40°C-100°C than Mobil 1™ Synthetic Gear Lube LS 75W-90 with a Viscosity Index of 171 compared to Mobil 1’s  146

Red Line 75W85 GL-5 Gear Oil compared to Castrol Syngear 75W-90 Synthetic Gear Oil

Red Line 75W85 GL-5 Gear Oil is 41.8% “thinner” (more viscous) at 40°C and 20% “thinner” at 100°C than Castrol Syngear 75W-90 Synthetic Gear Oil. Because the Castrol Syngear lubricant is thicker at 100°C it won’t flow as well, will increase friction and lower fuel economy. Overall, Red Line 75W85 GL-5 Gear Oil is more stable over the 40°C-100°C than Castrol Syngear with a Viscosity Index of 171 compared to Castrol’s  139.

A lubricating fluid or oil with a higher VI means the oil is more stable across a broad temperature range than the same “weight” oil with a lower VI specification. See this post for more information on Viscosity Index.

Will 76W90 gear oil work? Yes, but it will generate slightly more friction which will lower fuel economy.

There’s a better way.

Red Line Oil makes a synthetic 75W-85 GL-5 gear oil

Red Line’s 75W-85 GL-5+ gear oil is a genuine Group IV product red Line 75w85 gear oilmade from polyol ester base stocks, as opposed to a Group III product sold by many other companies. The ester base stocks and friction modifiers provide additional slipperiness to lower operating temperatures by reducing the sliding friction in hypoid gears.

What’s the difference between a Group III synthetic and a Group IV synthetic? See this post to see why Group IV is the real deal

Red Line 75W-85 GL-5 Vehicle Compatibility

Acura
2012-2014 TL SH-AWD
2013-2018 MDX

BMW
2012+ 1 Series, 3 Series and Z4 w/o LSD differentials

Chrysler
2005-07 Crossfire rear carrier/drive assembly & front/rear differential
2015+ 300 rear differential

Dodge
2015+ Challenger, Charger rear differential

Dodge Truck
2007 gas medium & heavy duty & diesel equipped with C205F front differential

Ford
2016+ Focus RS rear differential
2013-2014 Shelby GT500, 2015+ Mustang differentials
2014+ Raptor, 2016 F150 rear differential

GM Vehicles
14+ Chevrolet Silverado 1500, GMC Sierra 1500 rear differential
15+ Cadillac Escalade, Chevrolet Suburban, Tahoe, GMC Yukon, Yukon XL rear differential
15+ Chevrolet Express Van 2500/3500 rear differential w/o dual rear wheels
14+ Chevrolet Caprice, SS rear differential

Mercedes-Benz
2007+ C, GL ML, 2011+ CL, E, GL and R class differentials

Suzuki
2007-08 Grand Vitara transfer case
1999-06 Grand Vitara, XL-7 front differential
1999-07 Vitara differentials

Toyota
2003-08 4Runner front and rear differentials
2003-08 FJ Cruiser front and rear differentials
2008 Land Cruiser front differential

Where to buy Red Line’s 75W-85 Fully Synthetic Gear Oil

Purchase from these authorized dealers or special order it from NAPA, Advance Auto Parts, Autozone, O’Reilly Auto Parts, Mighty Auto Parts and CarQuest

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Posted on by Rick Muscoplat



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