Towing with Your Yaris

[crk06c]

Before I get flamed, allow me to state my credentials.

I am a student of Physics, hence I understand the basic mechanics involved in automotive systems. I am intently focused on a Master’s in Mechanical Design. Having a 15 year old car, I have performed nearly every task a mechanic is trained for. But most importantly, I have towed with the AT Yaris LB!

Not only did I tow, but I towed a 4x8 U-Haul trailer from Florida to California, and the trailer was completely filled. A few things need to be considered when realistically evaluating the impact towing will have on a car.
First of all, the force resisting the motion of your vehicle is proportional to the trailer weight, but not equal to it. The weight of the trailer will cause friction in the wheel bearings, but this friction is much less than the weight of the trailer.

Second, your car is strong. These engines are designed to schlep you and your crap around the city, up and down hills, in what are often very unhealthy conditions for your engine.

So here’s the story:
My girlfriend of 5 ½ years graduates and moves to L.A. She owns a cute little Yaris, and wants to know how to get her car, her puppy, and all her stuff to L.A. So I bought a hitch and rented a trailer, and now I’m writing this from L.A.!

On day one, we drove 6 hours from Tallahassee to New Orleans. Warm, but humid, air kept the engine cool enough, and the transmission seemed hardly affected. Gas consumption was somewhere around 30-33 mpg. On day two, we drove 9 hours to San Antonio. Driving through the moist bayou air was great for the radiator, drawing heat away much more quickly. That was not true for day 3. We drove 9 hours to El Paso, by the end of which there was a noticeable coat of engine oil on the block. The dry, mountain air, though cool, couldn’t stand up to the heat from climbing mountains against headwinds. This leak was caused by overheating oil, which my girlfriend proposed we control by turning on the heater. Great idea. Given 8 hours to rest, day four went great. After about 15 hours on the road, there were no more oil leaks or problems of any kind.

So what can be learned? Evaporative cooling from moisture in the air gives great cooling advantages. Dry areas, even if cooler, won’t cool the radiator as well. Too bad humidity can’t be controlled. What to do? Drive slower. We saw expected changes in temperature going up to 60 mph. After 60 mph, the engine temperature would increase rapidly. If you’re towing, keep the speed down. And as far as the oil leak on day three, I estimate we lost about 0.25 quart of oil for the duration of the trip. The leak came from a preexisting problem spot on the valve cover gasket. When the synthetic oil I use heated up enough, it started to do its job: seeping into the little nooks and crannies. My advice would be to install an oil cooler.

So, if you’re brave enough to try, here’s the summary:

Get a transmission cooler
Get an oil cooler
Do a thorough check for leaks
Be sure of your brakes and tires
Don’t go more than 60 mph
If it’s hot outside, turn on the heat and open your windows
Load your trailer properly, with 9%-11% of the weight on the tongue