We own a 2003 Ford Focus with 11,500 miles as our second car. We use it to carry the kids to school (a 35-minute round trip) and to do local errands. As such, we drive it only about 7,500 miles a year.

We get different advice on how often we should change the oil. The manual says every 5,000 miles with no time advice. The local oil jockeys say every 3,000 miles or every three months. The local dealer says every 3,000 miles or every six months.

I say go with the manual, but change the oil at least once a year. My wife says go with the dealer. We both agree that the guys who make money just changing the oil want to see our shiny faces and pocketbook more often than needed. So, for the $30 question: How often should we change the oil?

-Andrew Shogren, Sequim, Wash.

With the 35-minute round trip each day the Focus receives, your motor oil should heat up sufficiently to burn off most of the stop-and-start contaminants. My personal regimen, with two 35-minute daily commutes, is every six months for an oil change, regardless of the mileage. (I rarely exceed 6,000 miles during that time.)

While a believer in taking good care of a vehicle, I think the money and effort spent on an every-3,000-mile oil change could be better spent elsewhere, like cooling and brake system maintenance (renewing fluid) every 36,000 miles, renewing belts and hoses before they fail, staying on top of tire inflation pressure, applying a frequent coat of UV-inhibiting wax to painted surfaces, keeping the seat seams free of sand and grit, and so on.

Lubrication-related failures are minimal these days, compared with all the other more minor things that can sneak up on you. Folks who should consider a 3,000-mile oil change are those who rarely warm up their engine fully, drive in dusty conditions or tow/haul heavy loads.



Is it OK to install a larger battery in your car without also installing a larger alternator? I play my system (radio) a lot while playing ball at the park or washing my car, and was told I should look into this.

-Susan Beltran, San Jose, Calif.

Susan, with your greater-than-average engine-off electrical usage, a larger battery might be a good idea, if one will physically fit within the battery holder.

As long as the engine is starting normally (rapid and reliable cranking) after an outing, you should be fine. If slow cranking is noted, it might be time for a new and possibly larger battery.

Think of your battery as a savings account and your alternator as a checking account. The battery provides energy to start the engine (a huge electrical load) and meet the needs of engine-off electrical loads. The alternator dispenses funds for a variety of engine-running electrical loads – on a continual basis – and replenishes the battery from starting and engine-off activity.

A larger alternator might be a good idea for those with heavily used multiple batteries or greater-than-average engine-running loads, but would be overkill in your situation

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif.