On a warm and clear Saturday morning, Kurt Busch led the first of two rounds of practice for Sunday's night's Coca-Cola 600 at Charlotte Motor Speedway (FOX, 5:30 p.m. ET).

Busch, the 2004 NASCAR Sprint Cup Series champion and driver of the No. 41 Stewart-Haas Racing Chevrolet, lapped the 1.5-mile Charlotte track at 191.002 miles per hour, tops in the 40-car field.

Second fast was Jimmie Johnson, who leads all active Cup drivers with seven points race victories at Charlotte. Johnson's best lap in the No. 48 Hendrick Motorsports Chevrolet was 190.617 mph.

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Next was a pair of Toyotas, pole-sitter Martin Truex Jr.'s Furniture Row Racing entry and the Joe Gibbs Racing Camry of Carl Edwards. Ricky Stenhouse Jr. completed the top five.

Dale Earnhardt Jr. had to head to the garage shortly after the midpoint of practice after his 's Hendrick Motorsports Chevrolet began smoking heavily. A faulty seal in the power steering box was blamed as the culprit, as Earnhardt ended up 18th in the session.

With 600 long miles ahead on Sunday night, when race conditions will be very different, many teams opted to be conservative in the amount of laps they ran in practice Saturday morning.

The final Happy Hour round will take place at 1 p.m. ET and will be televised live on FS1.

For full results from the first of two Satruday practice sessions, see below.