When oil light flicks on, don't ignore it

Q I have a 2004 Dodge Intrepid and while I was driving it the oil light flickered a few times, then turned on and stayed on. I pulled over and checked the oil and it was full. I get it changed every 3,000 miles religiously. I was only a few blocks from my home so I drove it to my house and noticed it was knocking, kind of like the sound when your car is low on oil. Does this sound like an issue with the oil pump? Do you have any ideas on what the issue might be or what I could do to try to fix it?

A Ouch! Knocking sounds from an engine are never a good sign. Regardless of the fact that the engine was full of oil, you should not have driven the car with the oil light illuminated. With most engines, the oil light -- which monitors engine oil pressure -- will come on if oil pressure drops below about 6 pounds per square inch. Considering that normal operating oil pressure is generally in the 30-to-60 psi range while driving and perhaps 15 to 25 while idling, putting the engine under load by driving with oil pressure so low can cause damage to engine bearings and other expensive engine parts.

The oil pump may well be the cause for the sudden drop in oil pressure. Or there might be a problem with the oil pressure relief valve or oil filter itself. Regardless, don't drive the car -- don't even start the engine. Have the car towed to a competent dealer or shop for inspection. It may be necessary to pull the oil pan to visually inspect the oil pump and bearings. If there's significant damage, well, I sure hope your car is still covered by warranty.

The message for all of us is to take heed of the warning lights, particularly the coolant temperature and oil pressure warning lights. If either -- or both -- illuminate while driving, stop safely immediately and do not start or run the engine until the problem is identified. Yes, this may be inconvenient and require having the vehicle towed, but it will cost far less than having to replace the engine because of additional damage from driving.

Q I received an advertising offer with my credit card bill for an item that is manufactured in China and costs $19.95. As described, it will "Safely start your car's dead battery without opening the hood. Simply plug into your car's DC power port (or cigarette lighter socket) then into the other car's DC power port." Further, it says "Throw away those old, dangerous jumper cables for good." I gather from how the item is described that it can be used to jump-start another vehicle. Can that be a proper use of a power socket?

A There is no way any 12-volt accessory/cigarette outlet in an automobile can safely carry the necessary amperage to start a car with a dead battery. With that said, it would be possible to use a cable set like you've described to recharge the dead battery. Considering that most 12-volt accessory outlets in automobiles are protected by 15- to 30-amp fuses, it likely would take a significant period of time to recharge the dead battery enough to start the engine.

Speaking of jumper/booster cables, make sure you've got a set of heavy-duty cables -- 8 gauge minimum, 6 or 4 gauge even better -- in your vehicle's trunk at all times. Remember Murphy's automotive law: If you have them in the car, you'll likely never need to use them!