Find the right oil before you pour

Clear guides to gear oil, hydraulic fluid, motor oil and AC oil, checked against specs, standards and real owner feedback.

1,005 guides 4 checks on every product Updated October 2026
What does the grade mean?
75WCold flow rating. Lower flows better in winter.
90Thickness when hot, at 100 °C.

Gear oil. The most common grade for rear axles and many transfer cases. Check whether your gearbox needs GL-4 or GL-5.

See 75W-90 guides

Start with your machine

Gear oils

Axles, differentials, manual gearboxes · 353 guides
80W-90 75W-90 GL-4 GL-5

Hydraulic

Tractors, log splitters, jacks, machines · 225 guides
AW-46 AW-32 AW-68 15W-40

Motor oils

Cars, trucks, small engines · 185 guides
5W-30 10W-30 0W-20

AC oils

Car AC, home units, air compressors · 193 guides
R-134a

Transmission

ATF, power steering, brake fluid · 18 guides
ATF

Tools

Pumps, extractors, injectors · 31 guides

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Gear Oils & Differential Fluids

All 353 guides
Guide
Gear oils

Gear Oil Weights

When it comes to maintaining the longevity and performance of your vehicle’s drivetrain, understanding gear oil weights is…
Guide
Gear oils

Gear Oil Weight Per Gallon

When it comes to maintaining the performance of your vehicle or machinery, selecting the right gear oil is…
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Gear oils

Gear Oil Weight Explained

Understanding gear oil weight is crucial for ensuring the optimal performance of your vehicle’s transmission. The right gear…

Hydraulic Oils

All 225 guides
Guide
Hydraulic

Hydraulic Oil Weight Per Gallon

Hydraulic oils are essential for the smooth operation of various machinery and hydraulic systems, from construction equipment to…
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Hydraulic

Will Motor Oil Work As Hydraulic Fluid

Motor oil and hydraulic fluid serve distinct purposes, yet many people wonder if motor oil can substitute for…
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Hydraulic

Hydraulic Oil What Is It

Hydraulic oil plays a crucial role in the machinery and equipment that power various industries, from construction to…

Motor & Engine Oils

All 185 guides
2005 Honda Odyssey Oil Change & Air Conditioning Problems: A Complete GuideGuide
Motor oils

2005 Honda Odyssey Oil Change & Air Conditioning Problems: A Complete Guide

It’s the middle of July. You load the family into your 2005 Honda Odyssey for a weekend trip.…
1994 Chevrolet Suburban Air Conditioning Oil Change: A No-Nonsense GuideGuide
Motor oils

1994 Chevrolet Suburban Air Conditioning Oil Change: A No-Nonsense Guide

You hop into your 1994 Chevrolet Suburban on a July afternoon, crank the AC, and all you get…
1982 Oldsmobile Cutlass Supreme Air Conditioning Oil and Recharge: A Step-by-Step GuideGuide
Motor oils

1982 Oldsmobile Cutlass Supreme Air Conditioning Oil and Recharge: A Step-by-Step Guide

You crank the blower on your 1982 Cutlass Supreme. Hot air hits you in the face. The compressor…

AC & Compressor Oils

All 193 guides
How to Add Oil to a Car Air Conditioning Compressor (Step-by-Step Guide)How-to
AC oils

How to Add Oil to a Car Air Conditioning Compressor (Step-by-Step Guide)

Your car’s AC blows warm. You check the refrigerant pressure and it’s fine. But the compressor sounds rough,…
How to Diagnose and Recharge the Air Conditioning on a 2005 Prius (ND11 Oil Guide)How-to
AC oils

How to Diagnose and Recharge the Air Conditioning on a 2005 Prius (ND11 Oil Guide)

Your 2005 Prius AC blows warm air on the hottest day. You have heard it is a hybrid…
How to Recharge the AC on a 2005 Toyota Prius: Refrigerant and Oil GuideHow-to
AC oils

How to Recharge the AC on a 2005 Toyota Prius: Refrigerant and Oil Guide

It is the middle of July. You are sitting in traffic, the sun is baking through the windshield,…