So which is it, John?

Well this month, I'm going out on a limb. I plan to use a little personal common sense and let you know how I feel about oil-coolers. Here's the official disclaimer: this is my opinion, and not the opinion of Mr. Ball, Sin Wu or anyone else. You are welcome to share in my ramblings, think I'm a genius, recommend me for a gold star, or feel free to shower me with praise next time you see me. At the same time, you are more than welcome to disagree with me, tell all your friends what an idiot I am, or scorn me for ever more. Different opinions make this an amazing country to live in, right or wrong.

Get to the point, John.

During the hot summer months, riders seek to insure that their bikes don't overheat. If you own an American bike, and its not a V-Rod, you've got an air-cooled motor. Most of our metric bike friends, and the V-Rod riders, have water-cooled engines. As basic as this sounds, either water and air, or oil and air cools your bike's engine. Why? I'll tell ya. Because you are being propelled down the road by an internal combustion engine. Combustion (the explosion) of your fuel (gasoline) moves the pistons in your motor, which generates heat. On top of that, the movement, in close proximity, of the internal components of your motor (rods, pistons, gears and the like) create friction, which generates additional heat. If you don't control the heat associated with these mechanical functions, all this metal stuff in your motor will melt together like candle wax and you'll end up on the side of the road. Not good.

Yeah, yeah, get to the goddamn point, John.

If you're reading closely, the common cooling feature found in either water-cooled or air-cooled engines is AIR. Air is the common denominator that cools your motor, whether you have just oil running through it, or oil and circulating water (anti-freeze coolant) flowing though pockets inside your crankcase. The ultimate goal is to dissipate the heat generated in your motor into the atmosphere.

Yippee, get to the point, will ya.

If you've got a water-cooled engine, you'll be sporting a radiator somewhere on your machine. Normally it’s a rather ugly piece of gear aptly named because it radiates the heat captured in the water that's circulating through your motor. A typical radiator is composed of thin circuits of compressed tubing through which the water or "coolant" flows. Air passes by the radiator fins, and the heat energy is dissipated into the atmosphere, so the coolant can once again flow into the motor to cool the hot cylinders. If your vehicle is sitting still and no air is flowing through your radiator, heat will build up and you'll overheat your motor. To alleviate this condition, vehicle manufacturers place electric fans in front of radiators to assist the flow of air. Flowing air is the most important component to transfer the heat.

This is all about cooling an American V-Twin, John.

Your American V-Twin is a time-honored, incredibly good-looking design, which incorporates an air-cooled motor. Confused yet? Yes, air does cool your motor, but it's also the oil in your motor that is circulating and dissipating the heat being generated. Most V-Twins have only a 3-quart capacity of oil that circulates in and out of the motor. If you're a quart low on oil, you've reduced your cooling capacity by about 30%. That's why it is very important not to run your bike low on motor-oil--even more so when it's hot outside. The oil is also flowing at a relatively low pressure in your motor. The oil pump, depending on the oil temperature, generates only 5 to 15 pounds of oil pressure. If you're oil is extremely hot, you'll loose oil pressure and that results in engine damage. Sounds like you need an oil cooler, right? Well, not so fast. I'm still trying to get to my point here, bear with me.

Oil lubes the engine. It doesn't cool the engine, John. If it did, the oil would be stored in a radiator-type contraption. What are you trying to say, John.

Air is the key to cooling your V-Twin. That's why your motor has large fins all around the cylinders, which add more surface area for wind to cool. This additional surface area that you see on your Harley type motor works just like a radiator on the water-cooled motor. Air passes over the fins when you're moving, and that cools your engine and it's components, including the oil circulating from your oil tank into your motor. If you've got an oil cooler it will add an additional "radiator" type unit, to your oil circulation system, to dissipate the heat stored in the oil.

Yeah? As far as I'm concerned that's cool.

As much as you'd like to run out and buy an oil-cooler, I'd advise you to keep your wallet in your pocket. Now, I'm finally getting around to my Covington Code regarding why I think you should skip putting an oil-cooler on your bike (see disclaimer above). An oil cooler only works if you've got air blowing through it. When you're moving, an air-cooled V-twin motor cools just fine, because you've got air blowing through it. The same principal applies to your accessory oil-cooler; it needs air to circulate through its radiator to cool your motor. The problem is that I've yet to see an oil cooler designed for a V-Twin that includes an auxiliary fan, like a water-cooled radiator.

Ah, your notion is beginning to slip, John. More fins from a cooler add surface area to the cooling process while the bike is moving. The only reason we have internal combustions engines is to "move". If you must stop, hopefully the oil and engine has cooled enough to survive the pause.

About the only time your bike is going to overheat is when you're sitting still, low on oil, or you're pondering another route to avoid the traffic jam you're stuck in. If you've got an oil-cooler on your bike, sitting still with your motor running, you'll be reducing the oil pressure by forcing the oil through the cooler. The whiz-bang oil cooler won't be cooling your oil because it has no air circulating through it, so you're in double "heat" jeopardy. Plus you've added about four more oil hose fitting locations creating more places for oil to leak from your bike. If you're leaking oil, you're loosing the cooling property and contents of your oil-bag and reducing the ability of your air-cooled motor to cool properly. Note: Harleys don't leak; they just mark their spot.

One of the reasons I run coolers is to enhance my motor oil capacity, goddamnit.

Last but not least, I can hear you "Oil-Cooler Advocates" yelling right now that it's 120 degrees out here in the desert, and you need all the help you can get. Bah-humbug. Your V-Twin is well designed to run at around 215 degrees of oil temperature. If the ambient air temperature is 90 or 120, your motor really could care less as long as it has air blowing through it, regardless of the air temperature. I'd rather have more oil pressure lubricating my internal combustion engine to keep me going, than a $150 oil-leaking accessory bolted to my bike that's not helping me cool my motor.

Okay John, but what about the Twin Cam engines that run 240 degrees plus? I installed a H-D cooler and tested it on the run to Barstow. It generally ran 20-25 degrees cooler. Is that bad? Plus the cooler and lines added to my 4-quart capacity.

In summary, I think the best thing you can do in the Desert Southwest is change your motor oil often, make sure your oil level is topped off, and avoid traffic jams. I also run 25/60-weight oil in the summer, vs. the standard 20/50-weight oil normally used in your late model bike to add an extra margin of heat protection that the higher viscosity oil will provide. I say keep your money in your pocket next time somebody tries to sell you an oil-cooler. Spend your cash on a date for those hot nights Give her a ride to the show on your bike, have a good time, the air-conditioning in the theater is amazing this time of year. That's way cool.

Here's a couple more thoughts to consider. The guys at the factory told me that H-D oil is rated to 360 degrees. During our test my brother's Evo dresser ran an easy 90 degrees less than the Twin Cam King. What does that mean? Evos are already cool? I'd rather run a cooler and be safe.

One more thought. Evos run substantially cooler, but with considerably less capacity. My Dyna only held about 2.5 quarts. If oil volume is a consideration and you're running 2.5, you could add to that number with a cooler.--Bandit

Keep the rubber side down,
John Covington
www.musclebikes.com

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