Updated

Tonight, 43 NASCAR Sprint Cup Series drivers square off during the longest race of the year, the Coca-Cola 600 at Charlotte Motor Speedway. This is arguably the toughest test of man and machine all season long, with hot weather and high humidity added to the grueling distance.

This race can be a heartbreaker, as Dale Earnhardt Jr. found out last year, when he ran out of gas while leading with less than half a lap to go.

Here are five favorites to win:

1. TONY STEWART — The three-time and defending NASCAR Sprint Cup champion loves hot, greasy weather, so tonight should play into his wheelhouse. He nearly won this race in 2008, only to cut a tire in the closing laps. Stewart won the Sprint All-Star Race at Charlotte in 2009 and his crew chief, Steve Addington, led Kurt Busch to victory in this race two years ago. Stewart was sixth in Happy Hour and will be tough tonight.

2. JIMMIE JOHNSON — There’s a reason they call Charlotte Motor Speedway, “The House That Jimmie Built.” Johnson has won six points races and three All-Star events here and is almost always the man to beat at Charlotte. Johnson has won two straight races, triumphing at Darlington two weeks ago and winning the All-Star race here last week. Johnson’s No. 48 Hendrick Motorsports Chevrolet had the best 10-lap average in Happy Hour.

3. MATT KENSETH — A past 600 winner, Kenseth and his Roush Fenway Racing team excel whenever they race at 1.5-mile tracks. Second in points, Kenseth isn’t always the fastest car out there, but he is very smooth and consistent and rarely makes a mistake. Kenseth was seventh in Happy Hour and third last week in the All-Star race.

4. BRAD KESELOWSKI — Another driver to keep an eye out for is Brad Keselowski, last week’s runner-up to Johnson in the All-Star race. Keselowski was fastest of all during Happy Hour on Saturday and is very confident in his Penske Racing team. Plus, he’d like nothing better than to give car owner Roger Penske a second victory on Memorial Day weekend to go with yesterday’s NASCAR Nationwide Series victory.

5. CARL EDWARDS — Even though he’s riding a 44-race winless streak, Edwards is about set to break out. The 2011 All-Star winner has been fast all weekend and was second in Happy Hour on Saturday. Like his teammate Kenseth, Edwards will have a fast car tonight.

Tom Jensen is the Editor in Chief of SPEED.com, Senior NASCAR Editor at RACER and a contributing Editor for TruckSeries.com. You can follow him online at twitter.com/tomjensen100.