738 lb-ft of torque, capped on purpose, bidding at $25,000

Good morning. Sometime today Washington finalizes a new fuel-economy rule, and a few hours later a 604-horsepower V12 roadster finishes its auction. The scheduling was not our doing.

Both stories are about what a number is worth once the thing behind it changes. A Mercedes that stickered at $185,775 now trades like a used sedan. A federal mpg target is about to drop, sixteen months after the fine for missing it went to zero. And a family garage in Bavaria turned a piece of 1981 paperwork into cars that resell for several times their sticker.

In today's newsletter, we'll get into:

Let’s roll.

This morning's car is a black 2006 Mercedes-Benz SL65 AMG showing 60,000 miles, offered by a dealer in Douglassville, Pennsylvania. Bidding stands at $25,000 with a reserve in place, and the auction closes this afternoon at 1:31 p.m. Eastern.

The spec is the R230 SL with nothing held back: a twin-turbocharged 6.0-liter M275 V12, factory-rated at 604 hp and 738 lb-ft, driving the rear wheels through a five-speed automatic. Black over Charcoal leather with Black Ash trim, an Anthracite Designo Alcantara headliner, heated and ventilated multi-contour seats, Keyless Go, COMAND navigation, Bose audio, and 19-inch two-piece AMG wheels. Active Body Control and the AMG brake package with cross-drilled rotors are standard fare at this level.

The torque number deserves a footnote. It is a limit, not a measurement. The M275 could make more, and AMG capped delivered torque at 738 lb-ft (1,000 Nm) electronically to protect the transmission. That is also why a 2006 SL500 came with a seven-speed automatic while the V12 car kept the older five-speed: the older box was the one rated for the load. Inside the engine it is an unusual design for a 600-hp motor, with one camshaft per bank, three valves per cylinder, two spark plugs per cylinder, and water-to-air intercoolers. Twenty-four plugs and their coil packs are a known service line item.

The listing is candid about condition. The Carfax shows a "minor damage" entry from July 2025, the tires are a mix of Hankook and Nitto, the digital display screens show discoloration, and the seller posted a video walking through the cosmetic flaws. The history adds two more marks. The car has had eight previous owners, and the Pennsylvania title reads "Exempt" in the odometer field. That is normal for a 2006: federal odometer disclosure doesn't apply to model year 2010 and older vehicles. It also means the title doesn't certify the 60,000 miles, so the service records have to.

I own the car this one replaced. My 1999 SL500 is an R129, and the pneumatic HVAC valve block repair I wrote about in Issue #14 was a small, cheap version of a lesson that scales up badly on an R230. On Mercedes flagships of this era, the expensive surprises usually come from the systems around the engine: Active Body Control's pump, accumulators, valve blocks and struts, the hydraulics that fold the hardtop, and the electronics tying them together. A single ABC strut at dealer pricing can run into four figures. Anyone bidding should treat a recent ABC service record as worth real money, and a missing one as a line item.

The base sticker on this car was $185,775. At $25,000, it is trading for about 13 cents on its original dollar and about $41 per horsepower.

My call: This one finishes under $45,000. Eight owners, an accident entry on the Carfax, an odometer-exempt title, and a handful of cosmetic flaws all pull against it, and each gives a careful bidder a reason to stop early. The seller is what pulls the other way. This is a reputable dealer and one of the largest sellers on Bring a Trailer, and I have bought from them before. My low-mileage CL600 came from this dealer, arrived in incredible condition exactly as they described it, and is still my favorite Sunday driver.

On Saturday, President Trump said he had approved new federal fuel-economy standards, and Transportation Secretary Sean Duffy said the final rule lands today. As of Sunday night, the final numbers had not been published.

What the rule is. Corporate Average Fuel Economy, or CAFE, has required each automaker to hit a sales-weighted average fuel economy across everything it sells since 1975, a response to the 1973 oil embargo. The average is the key word: a company can sell thirsty trucks as long as enough efficient cars offset them.

The numbers in play. The Biden-era rule, finalized in 2024, would have taken the fleet target to about 50.4 mpg by model year 2031. The administration's December 2025 proposal set it at about 34.5 mpg. The final rule may or may not keep that figure. Neither number is a window-sticker mpg. CAFE is scored on older laboratory test cycles that read noticeably higher than the label on the glass, so a "50 mpg" fleet was never going to look like 50 mpg to a driver.

The part most coverage skips. The fine for missing the target has been zero since July 4, 2025, when the One Big Beautiful Bill Act reset the maximum CAFE civil penalty to $0, retroactive to the 2022 model year. Separately, the EPA finalized repeal of its vehicle greenhouse-gas standards in February, effective April 20. By this morning, the federal pressure on automakers to hit an mpg number was already mostly gone.

So why does today matter?

Both sides. The administration argues the Biden standards worked as an EV mandate and pushed up prices; NHTSA's own analysis of the proposal estimated about $930 off the average new-vehicle price. Critics point to the same analysis: roughly 100 billion additional gallons of gasoline burned through 2050 and about $185 billion in extra fuel spending. Environmental groups estimate the average owner spends more than $1,400 extra on fuel over a vehicle's life, before accounting for this year's higher pump prices. The midterms are five weeks away, and both sides are selling this as a cost-of-living story.

Watch-number: 34.5. When the text posts today, check whether the 2031 target survived from the proposal, whether the fuel-cost estimate was updated, and whether the rule says anything about the credits automakers already hold.

The Ferrari F40's body was eleven panels of carbon, Kevlar, and Nomex over a tubular steel frame. The Porsche 959, born as a Group B rally car, wore aluminum doors and front lid, a polyurethane nose, and Kevlar-reinforced panels nearly everywhere else. A modern Formula 1 survival cell is carbon fiber, with its flanks lined by a layer of Zylon, a high-toughness synthetic fiber doing the job Kevlar made famous. Three eras, same question: which fiber goes where?

On paper, they look close. Carbon fiber's tensile strength runs about 3.5 to 6.0 GPa. Kevlar sits at about 3.0 to 3.6 GPa. Kevlar is also lighter, around 1.44 g/cm³ against roughly 1.6 to 1.8 for carbon. If strength per kilogram were the only test, it would be a coin flip.

Stiffness decides most of it. Carbon's modulus runs from about 200 GPa to 800 GPa for high-modulus grades. Kevlar's is about 60 to 120 GPa. A chassis, a wing, or a suspension pushrod is designed to limit deflection, and at equal weight carbon deflects a fraction as much. Kevlar also has a weakness carbon doesn't share: its compressive strength is a small fraction of its tensile strength, because the fibers kink under load. Kevlar is a poor choice for anything that gets squeezed.

Failure mode decides the rest. Carbon stretches about 1.5% before it breaks, and it breaks suddenly. Kevlar stretches 2.5% to 4% and fails a strand at a time, absorbing energy as it goes. That sounds like carbon is bad in a crash, and for puncture it is. But in axial crushing, a carbon tube designed to fracture progressively absorbs several times what a steel one does per kilogram. That is why F1 noses and rear impact structures are carbon: they are meant to disintegrate in a controlled way.

The side of the tub is a different problem. There the risk is intrusion: debris, a wheel, or shards of another car's carbon bodywork coming through the wall. The FIA's answer is a bonded anti-intrusion layer of carbon and Zylon, roughly 6 mm thick, so the tougher fiber catches carbon fragments before they reach the driver.

Kevlar is a brand name for aramid, a family of synthetic fibers that also includes Nomex, the heat-resistant version used in racing suits and the F40's honeycomb panels. The same logic runs through the rest of the car. Aramid shows up in fuel-cell bladders, rally underbody protection, helmet shells, tire belts, timing belts, and brake pads, where aramid pulp replaced asbestos. Carbon shows up in tubs, wings, driveshafts, and crash structures.

Workshop realities. Kevlar is miserable to cut, drill, and sand: it fuzzes instead of machining cleanly and needs dedicated tooling. It absorbs moisture and degrades under UV, so exposed parts need a coating. Carbon is electrically conductive, which causes galvanic corrosion where it meets aluminum; a glass-fiber isolation ply at the joint is standard practice. For parts that need both stiffness and toughness, carbon-aramid hybrid weaves put carbon on the outside for rigidity and aramid inside to hold the part together after impact.

RUF Automobile started in 1939 as a service garage in Pfaffenhausen, Bavaria, founded by Alois Ruf Sr. It added a gas station in 1949 and, in 1955, a tour bus he built himself, which sold well enough to start a separate bus company. The instinct from day one was to diversify around the garage.

His son, Alois Ruf Jr., started servicing Porsches out of the shop in 1960 and took over at 24 when his father died in 1974. The first complete RUF car followed in 1977, a 930 Turbo stroked to 3.3 liters. In 1978 came the SCR, a naturally aspirated 911 stroked to 3.2 liters.

The paperwork that made the company. In 1981, Germany's federal motor transport authority recognized RUF as a vehicle manufacturer. The push came partly from Porsche, which did not want liability for cars RUF had re-engineered. The consequences compound to this day: factory-built RUFs carry their own VINs (the W09 prefix), their own manufacturer warranty, and their own type approvals. RUF bought bare bodies-in-white from Porsche and built complete cars around them.

That status paid off in a place nobody planned. From 2000 to 2016, Electronic Arts held exclusive rights to Porsche in video games. Because RUF was legally its own manufacturer, other franchises, including Gran Turismo, used RUFs as stand-ins. A generation of teenagers learned the name from a controller.

The Yellowbird. In 1987 the CTR hit 211 mph in a magazine top-speed shootout, beating the Ferrari F40's claimed figure, and later reached 213 mph. RUF built 29 from bodies bought from Porsche, plus roughly 20 to 30 conversions of customer cars. For decades they traded below F40s and 959s; one sold for about $1.02 million at auction in 2018. Then in March 2025, a 1,040-mile Yellowbird sold for $6.055 million, followed within months by sales at $4.68 million and $4.295 million.

How the business works today. Production is reportedly 30 to 40 cars a year. The revenue sits in several streams:

RUF keeps its capital needs small by partnering on the hardest engineering. Canada's Multimatic co-developed the mid-engine CTR3, Berlin's Vela Performance engineered the CTR Anniversary's chassis and body, and the monocoque itself is built by Gerg, a supplier to endurance-racing programs. Compare that with INEOS (Issue #26), which spent heavily to stand up a new vehicle program from nothing. RUF took 86 years and never needed an outside investor.

The rumor. In August, a German business magazine reported that Porsche was close to folding RUF in as a low-volume sub-brand. RUF denied it outright. Alois Ruf said the company is not for sale and remains family-owned and operated, with no plans for Porsche to acquire it.

That's a wrap. See you Wednesday — same inbox, lower gear.

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