Q. I have a 1966 Corvette and just heard from someone that these old engines need zinc in the oil to prevent wear. The problem, from what I understand, is modern oil does not contain zinc. I want to do the right thing for my car. What should I do and what should I buy? I have also heard of people adding a ZDDP additive to prevent wear, is this a good idea?

— Bill, Lincoln

A. There is a fair amount of misinformation about zinc in oil. Zinc is still in oil, but in limited amounts, depending on the API rating from the particular oil company. I spoke with David Canitz from the technical services department of Royal Purple Oil. David explained that the SL rated oils have the lowest amount of ZDDP at 800 parts per million. But for most “classic flat tappet cam engines,” he would recommend using the 10W40 or 15W40 oils, which are API CI-4+ /SL-rated and contain 1,300 ppm of ZDDP. In my opinion, I would not add a ZDDP additive. My concern is overdoing it with the additive; it is my belief that most additives work best when blended with the oil during production.

Strange starting trouble

Q. When I went out to start my truck yesterday morning, it turned over great but did not start. After many attempts, and the battery starting to weaken, I got into my car and went about my errands. I noticed that while the engine was turning over, a ground wire was heating up and emitting a little smoke. When I got home I cleaned the ground connection and it started right up. I went back and cleaned the wire to body-bolt connection, and then it didn’t start again. With my foot slightly pushed down on the throttle, the truck started but would not idle. I tried this three times with the same result. This reminded me of the time my battery died; even with a jump from AAA, it wouldn’t idle. It would start with throttle, but would not idle. I thought to disconnect the battery for a couple of minutes. Afterward, I reconnected the battery and it started right up and idled fine. What gives?

— TK

A. I’d still want to check all of the ground wire connections for corrosion. I have seen that in a few cases disconnecting the battery in effect “reboots” the computer and everything will be fine. The poor electrical connections “spike” the computer, causing poor operation. The other common problem with some of these trucks is a faulty coolant temperature sensor, or wiring to the sensor, which is certainly worth a look.

BMW oil level sensor

Q. I own a 2000 323ci BMW. Is it hard to change the oil level sensor switch?

A. This is a fairly simple repair. The oil sensor is held in place with three bolts. Drain the oil, disconnect the wiring harness, and remove the sensor. One word of caution — on some of these models the wiring, not the switch, is the problem.

Choosing tires

Q. I have a 2000 Saturn LW1 wagon with 145,000 miles and would like to buy a new set of tires for it. Where can I get a good price for a decent (not necessarily high-end, but safe and reliable) tire? I would like to go someplace that includes rotations, repairs in the price. Do you have a particular make or model tire you would recommend?

— Joyce, Providence

A. Many years ago, when I first started to repair cars, the best tires lasted 20,000 miles. Today even the most inexpensive tires can last 40,000 miles or more and they are all quite good. In general, I prefer to stay with a name brand tire for ease of replacement, should you need just one new tire and you are away from home. Tires made by Bridgestone, Goodyear and Michelin all do a great job. AAA has relationships with several tire stores. Go to aaa.com and then the “Show Your Card and Save” section for companies that offer AAA members discounts.

projocars@projo.com