The garage sure does harbor a lot of secrets.
Between shelves lined with boxes, fertilizer, grass seed and pesticide sit some lonely, unused and sometimes unopened bottles of engine fluids that were once lost but now found thanks to last weekend's garage clean-up day.
Lined with a fine layer of dust and perhaps smudged with oil, these bottles were once the star attraction on a maintenance day for your dirt bike or ATV a long time ago. Years went by and for whatever reason you never used the DOT 4 brake fluid again. You also have two jugs of coolant because the day after you bought some fresh stuff that half-filled container you totally forgot about was found. That always happens.
If you ride dirt bikes or ATVs or any machine in the powersports industry you likely have a garage full of tools and maintenance items like lubrication and fluid. Even if you own just one car, and use the local mechanic for all maintenance needs, you likely at some point bought some engine oil for topping off. Now that old quart sits there 80 percent filled.
Soooo. Can you use any of that old but unused fluid that settled in the garage during the last few years? Well, that depends.
What to do with Old Brake Fluid
The old school of thought with brake fluid that says "use what you need and throw out the rest" applies to some extent. Brake fluid tends to absorb moisture thus the standard recommendation of throwing out what you don't use. In reality, you can keep an open bottle of brake fluid as long as you tightly seal it after opening and use up to a year. (write the open date on the bottle to eliminate any second guessing later.) More than likely you won't ever use it again after opening, at least within the year time frame, thus the suggestion to simply throw the rest out because you probably won't ever need what's left. Check the color too. If the original color (varies among manufacturers but usually clear like mineral oil) bears a brown tint, get new fluid.
By the way, if you continually return to that opened bottle of brake fluid to top off you might have a leak or some other issue with your brake system.
If you bought brake fluid because it was on sale or you anticipated a future need but never opened it then keep it for next time, however after five years or more get your ride some new braking power.
What to do with Old Coolant
Coolant or anti-freeze offers the best shelf life of any of the fluids that keep your dirt bike or ATV running properly. An opened bottle lasts at least five years and an unopened bottle lasts 10 years or more. However, if you have mixed concentrate with distilled water toss this after a year or so. The water mixed with the concentrate, though required to perform optimally in the engine, eventually degrades the coolant's protective properties. You won't overheat, at least right away, if you use the older mixture but a hard day of riding especially on a hot day will test the coolant's limits.
Like the brake fluid, check the color and if it resembles a brown tint time to toss and buy new radiator fluid.
What to do with Old Oil and Other Oil-based Lubricants
Engine oil, premix, suspension oil, transmission fluid - anything petroleum based - lasts quite a while whether opened or unopened. The shelf life of most oil registers around five years or so and most of today's oil, especially synthetic, probably lasts longer.
The additives in oil eventually displace presenting the primarily problem with holding on to oil too long. Also, with the speed of technology the oil on the shelf today differs from the oil sold five years ago and will likely have different make-up in five years. Therefore, the 10w-40 engine oil or the 75WT transmission oil you bought five years ago probably has less protection than the same weight oil available today.
Bottom line: When in doubt throw it out. Or use it in your less persnickety lawn mower.
Hey! What about old gas? We covered that. Check out Using Old Gas in Your Dirt Bike or ATV