BMW xDrive unit with lifetime fill fluid

What Does Lifetime Fill Mean?

When I was a kid, my dad would have to take the car down to the garage every few months for a chassis lubrication, usually at the same time as the oil and filter change. Now, apart from a few components, the chassis lube is now a thing of the past.
Brake fluid reservoir
That kind of progress has been making its way to fluids, which are now commonly labeled as lasting for a “lifetime.”

What Does Lifetime Fill Mean?

The words “lifetime fill” raise a few questions, including whose lifetime — mine or my car’s? It’s a good question and one reason to read the fine print from your vehicle’s manufacturer. Lifetime fill doesn’t mean the fluid will last for 80 years. “Lifetime” refers to one of two things: what the manufacturer expects to be the average usable life of the vehicle or the life of your vehicle’s warranty. The exact definition of “lifetime” varies by manufacturer, but one thing they all have in common is that the fluids have a lower viscosity (i.e., they’re thinner). And they are designed to resist breaking down chemically as early as standard fluids do.

Common Lifetime Fill Fluids

While these long-lasting fluids vary by manufacturer, the most common ones are:

  • Rear differential fluid.
  • Transmission fluid.
  • Brake fluid.
  • Coolant.

Unlike the systems that replaced regular chassis lubrication, these aren’t always sealed. Depending on the manufacturer, you can usually refill or replace these fluids. But if your vehicle’s manufacturer says they’re lifetime fill, it means that you shouldn’t need to under normal operating conditions. If you operate your car under what the manufacturer considers “severe” conditions (whether you consider them “severe” or not), that lifetime fluid might require changes at very specific intervals.

For example, some manufacturers that offer lifetime rear differential fluids consider driving on dusty roads to be severe conditions. So, if you keep your 4×4 on pavement year-round, your fluid is good for a “lifetime.” But if you spend time off-roading or traveling on dirt roads, you may need to change your fluid regularly and on a schedule. If you use your vehicle to tow a trailer, your “lifetime” transmission fluid, brake fluid and coolant might not last as long. Again, check your owners manual and read the fine print.

The Pros and Cons of Lifetime Fill

The upside to using lifetime fluids is that you’ll have to do less maintenance over the life of the vehicle (or your ownership of it). The downside? If you start to get complacent about the fluids that do need replacement, such as engine oil, you’ll end up regretting it.

If you’re a DIYer or just particular about keeping your car in tip-top shape, consider replacing lifetime fluids occasionally — a periodic checkup on your car’s inner workings is not unlike bloodwork and other tests your doctor orders before your annual physical.

And if you’re a typical driver, lifetime fluid fills may give you peace of mind and one less thing to worry about.

Check out all the transmission fluids available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on lifetime fluids, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Wikimedia Commons.

about author

Mike Hagerty

Mike Hagerty is an automotive journalist whose work has been featured on radio, TV, in print and online since 1997. He's the Publisher and Editor of MikeHagertyCars.com, and contributes car reviews to the Los Altos Town Crier and losaltosonline.com. Previous outlets have included KFBK and KFBK.com in Sacramento, California, the ABC television affiliates and Hearst-Argyle and Emmis radio stations in Phoenix, Arizona; AAA magazines for Arizona, Oklahoma, Northwest Ohio, South Dakota and the Mountain West and BBCCars.com.

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