Dear Mike: With the cost of gas skyrocketing, I was wondering whether you had done a comparison on the new types of spark plugs on the market that claim to give you better gas mileage.

A: The only real improvement you’re going to see in fuel economy from a replacement spark plug of any sort is if the old plug is worn out and not firing. That wastes fuel.

Dear Mike: I have a 1995 Buick LeSabre 3.8 with 65,000 miles on it. The car will suddenly die. I have replaced the crank sensor, the electronic module and the fuel filter, but nothing has worked. Any suggestions?

A: Is the “check engine” light on? Have you checked for trouble codes? Is the fuel pump running when it won’t start? Is there spark?

You’ve replaced the crank sensor. Why? Blind parts-tossing, or did you have some reason to think that it was bad?

You’ve replaced the “electronic module.” Which electronic module? There are a dozen “electronic modules” on your car. Which one did you replace? Why?

Ditto for the fuel filter …

I’d start by hooking up a scan tool and running it in flight-recorder mode until the car dies. Then you’ll have some idea if the problem is with the fuel or the spark.

This is all systems analysis. You simply need to start at the top and diagnose.

Dear Mike: My 1997 Honda Prelude, with 155,000 miles, was just coming up to its 3,000-mile oil-change time and the red oil light came on. The oil was below the dip stick, so I added four quarts.

What could cause this, if there is no leak?

A: Let’s hope that you haven’t damaged your engine by starving it of oil.

Cars, even Hondas, consume oil. They consume more oil as they get older and the engine wears. Yours is old enough that it consumed four quarts of oil in 3,000 miles, letting the oil level get low enough to turn on the light. Your engine only holds five quarts.

Check your oil more often. Much more often.

Dear Mike: The battery in my 2006 four-cylinder Honda Accord went dead after not being used for about two months.

Can I charge it up using my 12-volt, 10-amp battery charger, by attaching its two cables directly to the two cables on the dead battery, without affecting the car’s electronics or computer?

A: Yes. Two months of not being run will pretty much discharge any car battery.

Be aware that being deeply discharged like this is hard on the battery. If you must leave it for long periods, disconnect the battery ground cable and/or use a maintenance charger.

Dear Mike: Does fuel-injector cleaner take care of condensation in your car’s gas tank?

A: Yes. But most gasoline in the U.S. now has a substantial concentration of ethanol to meet emissions or nonrenewable-fuel requirements, so water contamination/condensation isn’t the issue that it used to be.