As we've already seen, consumers have a lot of options when it comes to oil, and as you know, mineral or synthetic is one of the first decisions that must be made.
Crude-based oils, because of their natural origins deep within the earth, contain sulfur and other undesirable or harmful contaminants. A lot of these pollutants are removed from the oil during the refining process, but it's impossible to completely purify a mineral-based oil; it's simply too expensive and, thus, impractical, to design and invest in machinery that will filter the oil to a completely pure form. As we mentioned earlier, the remaining contaminants are one of the causes of motor oil deposits.
Synthetic oils, though much more expensive than their mineral-based counterparts, offer some advantages. Since they're not derived from fossil fuels, they don't deplete non-renewable natural resources. And because they're designed by chemists, they can be custom-blended to meet specific automotive needs, no matter how demanding. So if you decide to invest in synthetic oil, weigh the costs and benefits carefully. But while lab-engineered oil might be cleaner than crude-based, it's not still perfect.
Synthetic oil manufacturers want you to believe that their products are a miracle salve for every engine on the road. Synthetics do offer a lot of benefits over mineral oil, hence the much higher prices, so it's tempting to think you can make the investment but stretch a bit farther between oil changes. Bad idea, says Mike Allen of Popular Mechanics. Your engine might be a bit healthier if you're running synthetic, but gunk will still build up and cause problems. Stick to the manufacturer's recommended change interval, usually 3,000 to 5,000 miles (4,828 to 8,047 kilometers) [source: Allen].