Q. I enjoy reading your Saturday feature each week, and I just finished reading the piece in The Journal on Feb. 28 in which someone questioned the use of recycled motor oil in their vehicle.

I’m a shade tree mechanic, and I’ve never considered using anything other than new lubes in my cars. I own a 2007 Miata MX-5 with a power retractable hard top, bought from the showroom floor two years ago. It now has just a little over 10,000 miles on it. Because of the hardtop feature, I refuse to “cocoon” it during the winter. Although it stays in my garage when the snow flies, I will drive it on “dry pavement” days.

It’s a great head-turner, especially in its “arrest me red” color. You indicated in your 2/28 article that you use synthetic oil in your cars. When I first changed the oil in my Miata, I put in Pennzoil synthetic 5w-20. I’ve heard many opinions as to how many miles I should go between changes. One mechanic said that “motor oil is motor oil and should be changed after no more than 3,000 miles, even if it’s synthetic.” I decided that was too often, and change oil and filter after 5,000 miles. Is this too often with synthetic oil? Also, what brand of synthetic oil do you use in your vehicles?

A. Both cars in my family have recommended oil change intervals of 7,500 miles, and I try to never exceed this mileage. I continue to check the oil every 1,000 miles, and change it every 7,500 miles. For the last 10 years I have been using Royal Purple oil, and have been very happy with it.

Batteries last 3 to 5 years

Q. I have a 2004 Subaru WRX wagon with its original factory battery. Recently, during an oil change at the dealer, they tested it (an up-sell I’m sure) and found it to be at 65-percent capacity. I’m not sure what that means exactly, but they recommended replacement. I have yet to have any starting issue this past winter, or at any other time. What are your recommendations for changing the car battery, and what are the implications of waiting until next winter?

A. The typical life of a battery is three to five years. With a battery at 65-percent capacity, its life could be best described as marginal. Although most people think that batteries work hardest in winter, it is actually the hot weather that shows a battery’s weakness. Considering the battery in your car is five years old, replacing it is most likely money well spent.

Check crankshaft sensor

Q. I have a 2001 Caddy, and it will stall from time to time. I had it checked at a local garage and they replaced one of the crankshaft sensors. I thought the car was fixed, but about a week ago it stalled again. What do you think could be wrong?

A. I think you repair shop was on the right track. The most common problem with intermittent stalling is a faulty crankshaft sensor. The problem is that there are two sensors, and General Motors recommends replacing both sensors with an updated part.

Go ahead, buy the Daewoo

Q. What are your thoughts on buying a Daewoo Nubira? I can buy a 2002 model with very low mileage on it for about the price of a decent bicycle. Is this car worth it?

A. The Daewoo Nubira was made by a division of the Korean conglomerate that makes everything from ships to computers. In 2005, Daewoo was sold to General Motors and Daewoo stopped selling cars in the United States. Parts availability is always a problem when you buy a car that is no longer in production. There is a Web site, www.daewoous.com, that you can use to find parts. I did a search on the Web site and found Nissan of Smithfield, a former Daewoo dealer, is listed. I spoke with the parts folks, and they told me that so far they have been able to get nearly every part they have ordered. Based on this information, the Nubira may be worth a chance.

Reader update on mouse-proofing

The number 1 suggestion is fabric softener dryer sheets. Dave W. recommends not being shy, use plenty — maybe a box.

Many people suggested using old-fashioned “snap traps” rather than poison baits. Greg F. let me know there is nothing worse than a poisoned mouse that gets stuck in the heater or on top of the exhaust manifold. Don and Gen e-mailed to say vigilance is important; perform a mouse patrol on a daily basis. Finally, Bob said nothing is better than a “barn cat.” This is a cat that stays outside, and since he has had his cat — no mice, squirrels or chipmunks.

Thanks to all.

projocars@projo.com