Light-duty use of Toyota means tweaking oil-change algorithm

Dear Car Talk:

I bought my Toyota iM in February 2017 as a second car to our family RAV4. As of this morning, it has only 10,800 miles on it, with an average speed over that time of about 30 mph.

Essentially, I drive it to Kroger’s (one stoplight), CVS (two stoplights) and the golf course (5 miles on the highway).

At my dealer’s suggestion, I have them change the oil every six months, which means I average about 1,600 miles between oil changes. Under my circumstances, should I really change the oil every six months? Or should I do it every 5,000 miles?

The dealer says that in six months the oil gets stale, i.e. some moisture gets in there, blah, blah, blah. Is he spot on, or is he just blah, blah, blahing me? Thanks. — Terry

RAY: Hey, blah, blah, blahing people is my job. Tell this guy to butt out.

I think I’d land somewhere in between, Terry. Lots of modern cars now use their computer to calculate when it’s time for an oil change. It factors in not only how many miles you drive but how hard you drive and under what temperatures and engine operating conditions.

If your car had that capacity, Terry, I’d advise you to simply abide by that. Those algorithms are pretty good. Unfortunately, your little iM doesn’t have anything that sophisticated. It just has a “Maintenance Required” light that comes on, mechanically, every time the odometer racks up 5,000 miles.

So you’ll have to do your own estimating. And it’s not an exact science. Like those modern oil-change algorithms, I believe the degradation of your oil is based less on the calendar and more on how much work, and what kind of work, you’re asking the engine oil to do.

If you were driving a cab or towing a team of Clydesdales, you’d want to change your oil more frequently. But by any measure, you’re putting very-light-duty use on this car. Even if you’re carrying a set of golf clubs and a gross of extra balls to hide in your pockets, you’re babying this thing.

If I were you, once I got outside of the warranty period, I’d change the oil and filter once a year. That seems like a reasonable compromise. That’d be every 3,000 miles or so, which is more than good enough. Especially if you’re using synthetic oil, which I’d recommend.

You’re not doing any harm by changing the oil too frequently. But you’re wasting oil, oil filters, your time and your money. And you’re putting more waste oil into the world, and nobody needs that.

Cooling system keeps Chevy transmission calm and cool

Dear Car Talk:

Ever since I purchased my Chevrolet Traverse LT, I’ve noticed that the transmission temperature gauge regularly reads around 212 degrees at highway speeds. The engine temperature gauge reads normal or even a little cooler than normal — even when it’s hot outside.

I checked with the dealership and was told that this is normal operating temperature for this transmission. I worry that as soon as my warranty runs out, the transmission will expire.

Does this sound normal to you? I am constantly worried, while on long trips, that the transmission will give out in the middle of nowhere. — Ramiro

RAY: Don’t worry, Ramiro. It’s much more likely that something other than the transmission will give out in the middle of nowhere.

Actually, your dealer is right. This sounds perfectly normal. Here’s how your transmission stays cool: Whenever your engine is running, the transmission fluid gets pumped into the transmission cooler, which lives inside your car’s radiator. As the transmission fluid passes through the radiator (inside those transmission cooler lines), it essentially gets bathed in coolant. Once it’s cooled down, the fluid is sent back to the transmission to keep doing its job.

And do you know the temperature of that coolant that cools the transmission fluid? It’s about 220 degrees. It’s the same as your normal engine operating temperature, which is in the range of 210-230 degrees. Since the stuff that’s cooling the transmission fluid is 220 degrees, there’s no way the transmission fluid can end up cooler than that.

Think about it this way: If you had the air conditioner in your house set to 68 degrees, and you left a pitcher of beer out on your kitchen table all day, there’s no way it’s going to ever get any cooler than 68 degrees, right? Though I’m sure you’d drink it anyway.

If your transmission fluid wasn’t running through that 220-degree coolant in the radiator, it could heat up to 350 or 400 degrees or more. And then it would cook itself and your transmission.

But it sounds like your transmission cooling system is doing exactly what it’s supposed to do, Ramiro. Hope that knowledge helps you cool off a bit, too.

Got a question about cars? Write to Car Talk write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at

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