Even with routine maintenance, your vehicle will become more vulnerable to engine trouble as it gets older and puts more miles behind its wheels.

Once the engine starts to be more problematic, you're likely to consider whether you should get a new or used vehicle instead of continuing to pour money into your existing car. If the vehicle is still in decent shape overall, however, you might consider rebuilding the existing engine.

A mechanic may suggest an engine rebuild if the trouble is serious enough that the shop has to take apart the engine to replace a faulty component. Kelley Blue Book, an automobile valuation company, says a more complete rebuild will replace this part as well as any other components that are worn down. This work reduces the chance that another part will fail in the near future, leading to another expensive repair job.

The Car Care Council says rebuilding typically results in a more efficient and up-to-date engine. Original components are replaced with newer parts that either meet or exceed the performance of the old ones.

The organization says there are a number of benefits to rebuilt engines. Upgrading the components of the engine will result in improved gas mileage and lower levels of emissions. This option is also environmentally friendly, since it conserves the energy that would otherwise be required to discard your old car or build a new engine.

Though rebuilding an engine is more expensive than the typical repair job, the Car Care Council says it is economical in the long run. Depending on the type of vehicle, the organization says an engine rebuild can cost between $2,250 and $4,000 - about 10 to 20 percent of purchasing a comparable vehicle.

Rebuilding an engine will also extend the life of your vehicle, allowing you to drive it for several more years if the chassis and other essential components are sound. The work typically comes with a warranty covering at least one year or 12,000 miles. Other warranties might extend for three years and unlimited miles.

An engine rebuild is not the best solution for all engine trouble. In many cases, a more minor repair is sufficient to resolve an issue. In other cases, however, more extensive work might be necessary.

The main drawback to a rebuilt engine is that it contains a mix of both old and new parts. Greg's Engine & Machine, a repair shop in Copley, Ohio, says the older components may shorten the engine's life expectancy even if the newer parts are more efficient and reliable.

Kelley Blue Book says that if an engine is significantly worn out or damaged, you'll want to consider what's known as a remanufactured engine. This process does a more extensive job of replacing old parts, updating everything from the seals to the gaskets to the pistons.

If you decide to get extensive work done on your engine, seek out a reputable company for the job. Kelley Blue Book recommends looking for a company that is part of the Automobile Engine Rebuilders Association, a trade group specializing in restoring engines.

Drivers who use a rebuilt or remanufactured engine should be especially observant of its maintenance needs. Greg's Engine & Machine says these engines should not be subject to heavy stresses such as towing or long trips for the first 500 miles. You should also get the oil changed after this interval before resuming regular oil changes every 3,000 miles or three months.

A rebuilt or remanufactured engine can breathe new life into a car. The Car Care Council says that with proper maintenance, it might last as long as a new engine.

However, each driver's situation will be unique. While a revitalized engine might do wonders for some vehicles, it won't be of much help for cars where components such as the brakes and wheels are also in need of expensive repair or replacement.

Mike Allen, writing for Popular Mechanics, says you should find out how much it will cost to rebuild or remanufacture the engine. If you think the money would be better spent on a down payment toward a new or used vehicle, this might be the best option for you.