Auto part stocks have remained surprisingly resilient amid the S&P 500, a proxy for the broader stock market, tracking sharply lower into correction territory – down roughly 10% from its Sept. 21 high of 2,940.91. A round of better-than-expected third quarter (Q3) earnings and a perception that auto part stocks are less reliant on strong economic growth compared with other sectors, such as technology, may help explain their relative outperformance. The $130 billion-per-year aftermarket auto parts business provides these companies with mild cyclical fluctuations and slow trend consolidation.

Investors may also be impressed with how auto part companies are offering more servicing options to commercial customers, which helps combat increased competition from large online retailers such as Amazon.com, Inc. (AMZN) and Walmart Inc. (WMT) that can't provide the same level of technical expertise. "The battle of the titans between Walmart and Amazon.com Inc. is only just starting," MoffettNathanson analyst Greg Melich, told CNBC. "The smart companies are doing what they should do, which is lean into the more service-oriented part of the business on the commercial side," he added.

Investors who want exposure to this outperforming industry should consider adding one of these three auto part stocks to their portfolio.

O'Reilly Automotive, Inc. (ORLY)

O'Reilly Automotive, founded in 1957, is a leading aftermarket automotive parts, tools and accessories retailer that targets do-it-yourself (DIY) and professional customers. The company, with a market capitalization of $26.92 billion, sells both branded and private-label products throughout its 5,147 stores across 47 states. Missouri-based O'Reilly Automotive reported earnings per share (EPS) of $4.5 in Q3 – surpassing analyst expectations of $4.4 per share. Comparable store sales also increased by 3.9% over the period. As of Nov. 21, 2018, the company's stock has returned an impressive 39.71%, outperforming the specialty retail industry average by nearly 33%.

The April 26 earnings gap is the standout event on O'Reilly Automotive's chart in 2018. Since that time, the price has steadily advanced before consolidating during September and October. The stock recommenced its upward direction in early November but fell 5.13% during Tuesday's broad market sell-off to close below the 50-day simple moving average (SMA). Investors who wish to buy should look for an entry price at $330 – an area where the price finds support from an uptrend line connecting the April and October swing lows and a downward-sloping trendline above last month's consolidation.

Chart depicting the share price of  O'Reilly Automotive, Inc. (ORLY)

Advance Auto Parts, Inc. (AAP)

Headquartered in Roanoke, Virginia, Advance Auto Parts sells automotive replacement parts, accessories and maintenance items to DIY customers through its 5,372 retail locations. The auto specialty retailer beat the Street's top- and bottom-line Q3 projections and gave guidance of full-year revenue between $9.55 billion and $9.6 billion. Trading at $171.53 with a market cap of $12.5 billion and offering a 0.14% dividend yield, the stock is up a staggering 72.24% year to date (YTD) as of Nov. 21, 2018.

Advance Auto Parts' stock price has trended higher since late April apart from a period of consolidation during September and October. Those who wish to buy the stock should look for an entry point at the $167 level, where price is likely to encounter support from a multi-month uptrend line. Traders should consider waiting for the stochastic oscillator to give an oversold reading near 20 before purchasing.

Chart depicting the share price of Advance Auto Parts, Inc. (AAP)

AutoZone, Inc. (AZO)

With a market cap of $20.27 billion, AutoZone sells and distributes automotive replacement parts and accessories. The company, founded in 1979, has over 6,000 retail stores operating throughout the United States, Mexico and Brazil. AutoZone is positioned to increase its digital foothold in 2019 by forming a partnership with Walmart to create a specialty auto parts store on Walmart.com. Although the company's share price has not performed as well as the first two stocks discussed, its YTD return of 11.49% outshines the S&P 500 by over 12% during the same period as of Nov. 21, 2018.

A 200-point ascending triangle, which is a bullish chart pattern, has formed on AutoZone's chart throughout 2018. The share price broke above the pattern's upper trendline in early November but has since retraced back below this level. Investors should consider opening a position in the stock on pullbacks to the $750 area, where the price should find solid support from an uptrend line that joins the May and October swing lows.

Chart depicting the share price of AutoZone, Inc. (AZO)