Gearbox oil or transmission fluid?

The first question we’re going to cover before we get anywhere near debating what fluid or oil changes should or shouldn’t cost, is which one you actually need.

Gearbox oil? Transmission fluid? It’s two ways of saying the same thing, right?

Wrong.

There is a difference that can make or break your car

Transmissions, or gearboxes, can be manual or automatic. The type of fluid or oil each requires is unique, as they perform related, yet quite different tasks.

Using the wrong type of fluid or oil can lead to excessive wear and tear. In turn, that wear will reduce the life of your gearbox or transmission, and lead to early replacement and unnecessary expense.

Automatic transmission fluid (ATF)

Automatic transmission fluid is a complex fluid.

It contains not only the lubricants and detergents to keep the transmission running smoothly, but also operates as a hydraulic fluid for your transmission. In some automatic cars, it also acts as the hydraulic fluid for the power steering and 4-wheel-drive arrangement.

Because of the nature of its work within your automatic transmission, the ATF also needs to incorporate anti-wear additives to combat rust and corrosion. It also needs to be finder due to the cogs and gears are much smaller than in a manual gearbox.

And that’s not all.

Automatic transmission fluid carries many additional additives and extras compared to traditional engine oil. If you really want to know how many, and how much more work it carries out, here’s your list:

  • Dispersants and surfactants to protect and clean metal components
  • Viscosity improvers
  • Seal swell additives
  • Anti-foam additives
  • Anti-oxidant compounds
  • Cold-flow improvers
  • High-temperature thickeners
  • Gasket conditioners
  • Pour point depressants
  • And finally, some form of petroleum dye.

Manual gearbox oil

Gearbox oil lubricates your manual transmission while also protecting it from corrosion.

Due to the nature of the high friction between large moving components during manual gearbox changes, the oil carries anti-wear compounds. They generally feature sulphur, which gives them a strong and distinctive smell. Gearbox oil is a much thicker and heavier duty beast all round.

How to spot the difference between automatic transmission fluid and gearbox oil at a glance

Automatic transmission fluid is much thinner than gearbox oil, and because of the dye it contains, is usually red or green.

The easiest way to find out which it is is to read what it says on the label. If the oil you’re considering using doesn’t have a label, then do yourself a big favour and get rid of it straight away.

Any unknown oil or fluid has no place in your car’s engine or components. Get it recycled or dispose of it properly. Otherwise, you could well be poisoning your car.

Automatic transmission fluid replacement prices

A typical drain and refill of automatic transmission fluid could cost you anywhere around £150 to £200.

For performance cars, you’ll probably pay a little more, as you would expect. The prices will be dependent on the quality of fluid and parts, and any specialised requirements for your make and model.

When should you change your transmission fluid?

A change and refill—or transmission fluid flush— should happen at around 40k mile intervals.

If your car regularly pulls heavy loads (caravans or trailers), you might want to consider slightly shorter periods.

Whenever you change your ATF, you should also change the filter and pan gasket. Not all automatic transmissions have a filter, so don’t panic if you can’t find one.

A healthy ATF should appear almost clear and have a slightly sweet smell. If you apply a single drop to a paper towel, it shou