The cars

Three national series run three genuinely different cars, and muddling them up is the first mistake nearly everyone makes. The Cup car is a spec chassis (The current Cup car since 2022, a spec chassis with branded bodywork, built to cut costs and level the field.) wearing branded bodywork: every team buys the same parts from the same suppliers, so nobody can out-build anybody. That's F1 turned on its head, and it's why the racing is so close.

NASCAR Cup Series

A spec chassis with branded bodywork. No team can out-fabricate another, which is F1 in reverse, and it's the reason the racing stays this close.

Next Gen (Gen-7) · since 2022 Daytona 500

Chassis	Steel tube frame with integral safety roll cage, a single spec design every team buys
Length	4,912 mm (193.4 in)
Width	1,996 mm (78.6 in)
Height	1,280 mm (50.4 in)
Wheelbase	2,794 mm (110 in)
Engine	5.86-litre (358 cu in) naturally aspirated V8, front-engined, rear-wheel drive
Power	670 hp baseline; 750 hp at tracks shorter than 1.5 miles from 2026
Gearbox	5-speed sequential Xtrac transaxle (plus reverse)
Suspension	Independent rear suspension, the old solid axle is gone
Wheels	Single centre-locking 18-inch aluminium BBS wheels
Weight	1,451 kg (3,200 lb) minimum without driver and fuel; 1,542 kg (3,400 lb) with
Fuel	Sunoco Green E15, 98 octane
Tyres	Goodyear
Bodywork	Chevrolet, Ford or Toyota, symmetrical (older cars were deliberately skewed for left-turn aero)

Explainer Why the cars are deliberately slower than they could be. These engines are capable of well over 900 hp; NASCAR restricts them to 670–750. Going further would, in NASCAR's own words, cross into 'very short-mileage engines'. The industry put the cost of exceeding 750 hp at $40–50 million. Counter-intuitive if you were raised on F1's power-unit arms race. Here the governing body caps performance to keep costs sane and the field close.

Explainer What changed for 2026. Horsepower rises to 750 at tracks shorter than 1.5 miles, the short tracks and road courses where drivers wanted more throttle to work with. And A-post flaps, previously only required at superspeedways, are now mandated everywhere to reduce the chance of a car getting airborne.

Explainer Why it exists. Next Gen replaced the previous platform to lower team costs, broaden parts availability through single-source suppliers, and make the series more attractive to new manufacturers. That last point is live. The horsepower rise is widely read as groundwork for a Dodge return to Cup, though nothing is confirmed.

NASCAR O'Reilly Auto Parts Series

One rung below Cup, and a completely different car: an older-generation chassis with a composite body, less power and less aero. Cup facts don't carry over.

The second-tier car · since Composite body era, 2018+

Chassis	Steel tube frame, the pre-Next Gen construction Cup left behind
Engine	5.86-litre pushrod V8, restricted below Cup output
Gearbox	4-speed manual H-pattern, drivers here still shift with a clutch
Wheels	15-inch steel wheels with five lug nuts, pit stops look different from Cup
Body	Flange-fit composite panels
Note	This is where Cup's future stars (and a few of its veterans) race on Saturdays

Explainer Why the name keeps changing. This series is named for its title sponsor, so it's been the Busch Series, the Nationwide Series, the Xfinity Series and, from 2026, the O'Reilly Auto Parts Series. Same series, new sponsor. If someone says 'Xfinity', they mean this.

NASCAR Craftsman Truck Series

Pickup-truck silhouettes dropped over a race chassis. The wildest racing of the three national series, and traditionally where careers start.

The race truck · since 1995

Chassis	Steel tube frame, similar generation to the second-tier car
Engine	5.86-litre pushrod V8
Body	Truck silhouette, Chevrolet Silverado, Ford F-150, Toyota Tundra, and from 2026, Ram
Aero	Tall, blunt bodies punch a huge hole in the air, the draft is enormous, so the packs run close
Note	Ram's 2026 entry is the first new manufacturer in a NASCAR national series in years

Explainer Why Ram matters. Ram returns to the Truck Series in 2026, the first manufacturer expansion in years, governed by NASCAR's new-OEM testing rules (limited tests, teams and vehicles, completed by March 1). It's widely read as Dodge testing the water for a Cup return. Watch this space.

Specifications from the Next Gen technical documentation as summarised on Wikipedia, plus NASCAR's 2026 technical bulletins. The rules move about a fair bit, so these figures get re-checked whenever the rulebook does.