Give thanks to Dad for warming tip and warm memories

Dear Car Talk:

Growing up, my dad taught me how to do oil changes, and I’ve been doing them ever since (40 years now).

When he taught me, he would let the car run for a bit to warm up the oil so it would drain out more easily.

Today’s cars use an oil that has a very low viscosity rating. So, is running the car prior to an oil change still necessary?

— Tom

Good question, Tom. It’s not absolutely necessary, but I do think it’s desirable.

You’re right that oil has gotten thinner (less viscous) over the years. Forty years ago, people were using 10W-40 or even 20W-50 oil. That means the oil behaved like a heavy, 50-weight oil in hot weather and like a 20weight oil in cold weather.

Now, most cars use 5W-20 or even 0W-20. Because of advances in technology, these oils do a better job of lubricating the engine, while creating less friction and drag on the moving parts. That improves efficiency and fuel economy.

So, if you drained the oil from a cold engine today, you might see more oil come out than would have come out in the 10W-40 days. But, more importantly, oil holds dirt and contaminants in suspension. When a car sits for a long time, some of that dirt can precipitate out. And the whole idea of an oil change is to get the dirt out of your engine, along with the dirty oil.

By running the car for five or 10 minutes, you get the oil to collect and hold in suspension any dirt and debris that’s on the inside surfaces of the engine. When you drain out that warm oil, the maximum amount of dirt comes out with it. So, I always run a cold engine for five or 10 minutes before draining out the old oil.

Keep in mind, Tom, the idea is to get the oil warm enough to grab up the dirt but not so hot that you end up in the Shriner’s Hospital Burn Unit.

Dear Car Talk:

A friend got new tires for her car but balked at the charge of $70 for tire balancing. How important is it to get new tires balanced? Thanks, I enjoy your column.

— Norman

Did you ever stay at one of those roadside Motel 4-and-a-half places in the old days, Norman? And did you ever put a quarter in the slot next to the bed to make it vibrate? Did you like that? If so, skip the balancing, because that’s how your car will ride with unbalanced tires.

The reason tires need to balanced is because no tire comes off its assembly line absolutely perfect. Good quality tires need less balancing than cheap tires, but they all need some.

The problem is, as the speed of the tire rotation increases, those imperfections in weight distribution get amplified throughout the car. And, even just a tiny bit of extra rubber in one spot will cause a major tooth-clattering vibration by the time you’re going 65 mph.

So, you offset or “balance” those imperfections by putting small weights on the wheel. There are several types of balancers in use these days. There are still some ancient ones, where the wheel is spun very slowly, and a bubble level indicates where the weights should get hammered onto the steel wheel.

The majority of balancers now are high-speed, computerized balancers, that spin the wheel very fast and tell the mechanic exactly where and what weight to glue onto the inside of the wheel. And, the best machines are road-force balancers, which simulate the effect of the weight of the car on the wheel and tire. Those also can be useful for diagnosing hard-to-solve balancing issues.

If your friend’s mechanic had a high-speed or roadforce balancing machine, $70 for four wheels is about the right price. The good news is that the machine will still be there when she goes back next week to complain about her ride.

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