Motorcycle Fluids: A Wet and Wild Bunch

by Lee Meyer

Let’s talk about fluids. Motorcycles are full of them. They are not all equal.

There are so many brands of engine oil. Which ones will work for you? It will depend on the particular design of your bike’s engine. Here’s why. Many bike designs have the clutch and transmission turning in the same case and oil as the engine. Clutches and gears chew up and contaminate inferior oils rather quickly. Most automotive grade oils are not up to the task and will break down much sooner than you might think. For this reason use an oil specifically engineered and labeled for motorcycle use. This includes synthetics. Most automotive synthetic oils have never been tested on motorcycles, and bikes were not even a consideration when these lubricants were engineered. Now, if the transmission on your bike is separate (Harley-Davidson, BMW) and does not share oil with the engine, most good quality oils will work fine as long as the manufacturer’s viscosity recommendations are met. Dealers will, of course, tell you that only their brand of oil will work and anything else will most certainly cause catastrophic engine failure. Whatever.

How often should you change that oil? It depends, but at least once a year even if the bike just sits. Oil will get moisture in it. Personally, I aim for an oil change every 1000 miles. Usually it ends up being 1500-2000 miles by the time I get around to it. This is admittedly too frequent for most riders, but I ride a lot of stop and go city miles and am quite hard on machinery. For most people 2000-3000 miles between oil changes is good. If you are traveling and you just happen to be in Nowhere, USA when your bike is due for an oil change, don’t get too worked up. Highway miles are not as hard on engines as stop and go traffic. You can probably wait until you reach your destination. There are occasional emergencies though when you can’t wait. I once found myself in Nagoles, Arizona needing an oil change pretty badly. There were no bike shops to be found, so I had to use car oil. The only car oil I know of that meets motorcycle standards is Kendall racing oil. Luckily, I found some. Good clean oil is cheap insurance and the lifeblood of your engine. Why wait until it turns black with grime before you change it? It makes more sense to change it before it gets nasty.

Gear oils are found in separate transmissions, shaft units, etc. The way I see it, gear oils are pretty much equal. Just use the proper viscosity and make sure it has a friction additive if your clutch operates in it. Automotive stuff is fine. Some oils have the friction additive in them already, or you can buy the additive separately and add it yourself. It is sold pretty much everywhere, even K-mart.

Coolants are not equal. Motorcycle coolant is pre-mixed and costs eight bucks a quart. Car coolant is straight and can be had for five bucks a gallon. When mixed 50/50 with water you will have two gallons for five bucks…DON’T DO IT! First of all, two gallons is pretty much a lifetime supply for one bike. The stuff will rot in the jug before you use it all. The motorcycle stuff will not corrode anything or harm any delicate seals or gaskets in a bike. The car stuff may or may not depending on the brand. I don’t know which brand will or will not harm what, do you? I’m sticking with the bike stuff. Change your bike’s coolant once a year, and check your manual when filling the system. Air can be stuck in pockets and must be bled out. Certain makes have bleed screws in areas that trap air. Always run the bike to operating temperature after filling the coolant, then let it cool before rechecking the coolant level.

Clutch and Brake fluids should be changed once a year. Use the DOT number your vehicle requires, usually DOT 3 or DOT 4. Automotive and motorcycle brake fluids are exactly the same. Other types, such as DOT 5, can be a pain and unnecessary. They spout off about having boiling points at a billion degrees or so, not harming paint and coming in some funky color like purple. If you are in a situation where you’re on the brakes hard enough to actually boil DOT 3 or 4 brake fluid, you get the squid of the week award and headlines in the morning paper, because you didn’t live through it. DOT 3 and DOT 4 can harm paint and, if left on long enough, even remove it. How about this: Don’t spill! If you have some kind of nervous tick or epilepsy, get a friend to help out. DOT 3 and DOT 4 do not mix at all with DOT 5. Therefore, before using DOT 5 in a system previously containing DOT 3 or 4, you should disassemble the whole brake system and remove all remnants of the old fluid. DOT 5 also tends to suck up moisture, so it should be changed more often because of this.

Fork oil requires a more lengthy discussion, so we will go into that another time.

Ride on.


PS: Most of us have thought about performing our own maintenance tune-ups. I have been considering a two-part article on this, and I could use some reader input. Please tell me what you’re riding (or interested in). Some info. you could provide: Type of Bike (cruiser, sport, touring, standard, etc.), Make (American, Japanese, Italian, British, etc.), Era (60s, 70s, 80s, 90s, etc.) Engine (Inline 4, V-4, V-Twin, etc.). Your feedback can help us help you. After all, a tune-up article on the Ariel Square Four wouldn’t benefit too many riders now, would it? Thanks.



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