Money miser wonders how long to wait between oil changes

Dear Car Talk:

I change the oil in our cars, mainly because I'm too cheap to pay what oil-change shops charge. Is there any way to test to see when the oil in a vehicle is almost worn out? Our cars vary widely in their use. One does a daily 15-mile commute; another goes 60,000 highway miles a year; and a van goes 3,000 miles or so a year, at times pulling a small camper. Sometimes the oil I drain looks like new. With oils and filters being so good these days, I'm wondering if I'm wasting time and money. If there were some litmus test for oil, it would be helpful, rather than simply going by miles. Thanks from a fan for decades. – Pat

RAY: There's not really a good litmus test, Pat. For ages, we've always estimated with miles and months. For a long time, our recommendation was to change the oil and filter every three months or 3,000 miles. But that recommendation is completely outdated now. With conventional oil, you can go six months or 7,500 miles. And with synthetic oil, you can go 10,000-12,000 miles, or a year. Some say more.

But now a lot of cars have their own, built-in oil life indicators. They work in different ways, depending on the manufacturer. Some use a direct measurement of some kind, testing the conductivity of the oil, the soot concentration or the presence of water. Other systems keep track of your mileage, the number of times you start the car and the temperature conditions under which you drive. They feed all of that data into an algorithm, and then tell you when it’s time to hit Pokey Lube.

Those systems seem to work well, and can help you cut down significantly on the frequency of your oil changes, based on real evidence rather than guesswork. So you might want to make sure that your next vehicles have those systems, Pat.

As for an aftermarket “litmus test,” where you wipe some magic test strip on the dipstick and find out how much oil life remains and whether you soon will meet the girl of your dreams, I haven’t found anything I’d be willing to really rely on yet, given that the downside is a ruined engine. It’s just not a risk I’d feel comfortable taking with my own car.

If I were you, I’d switch to synthetic, just to reduce the amount of time you spend lying under those three cars with hot oil running down into your armpit. And keep changing the oil based on your best estimates. After all, even several extra oil changes over the life of a car are cheaper than an engine rebuild.

In cold weather, car literally freezes out driver

Dear Car Talk:

I have a 2004 Hyundai Accent two-door. This is a winter question that I'd like to get fixed now, before it starts happening again. When the temperature drops below freezing for more than a week, I cannot open my doors from the outside. I have to crawl through my trunk and open the doors from the inside, or leave a window open so I can reach in and use the inside door handle. I cannot afford to get it fixed right now, but I am tired of crawling through my trunk. What is wrong, and is it an expensive fix? Thank you. – Kathy

RAY: That must be quite a show you're putting on for the neighbors every morning, Kathy. We'll look for you on YouTube.

There are lots of problems that can crop up inside old car doors. One possibility is that the latch mechanism itself is freezing. That’s the easiest thing for you to fix yourself, Kathy.

You just open the door, and at the edge of the door (the edge that faces toward the back of the car when the door is closed), you’ll see the latch mechanism. Start by spraying that with some WD-40 to clean it up and remove any dirt and moisture that you can. And then spray it with some lightweight lithium grease to lubricate it and repel moisture. You can get both of those things at any auto-parts store or department.

If that doesn’t fix it, then the problem is inside the door. There are a bunch of rods and levers that connect the outside door handle to that latch mechanism. On old cars, they can get sloppy, rusty, bent or broken, so that the motion of your hand on the door handle is no longer getting transmitted to the latch. And if there’s water in there, all that stuff can freeze, too.

The solution for that is to remove the inside door panel and expose the inner workings of the door. Once the inside of the door is exposed, you can have someone operate the handle, and you’ll see what’s moving easily and what’s not. Then clean up everything you can, spray it with WD-40 (I would not use lithium grease on that stuff) and hope that keeps it from freezing.

The hardest part of that job is getting the inside door panel back on. It attaches with a bunch of clips, and you never end up with the same number you started with. And if you do leave the door panel off – which you can – you have to be careful not to get grease or WD-40 all over the left side of your clothes when you’re driving.

But if it’s a choice between elbowing in through the trunk and driving with a poorly attached inner-door panel for a while, I think I know which one I’d choose. Good luck, Kathy.

About the Author