The R10's predecessor, the R8 Le Mans Prototype, was an open-cockpit design based on experience gained with the Audi R8R. The closed-cockpit R8C sibling was less successful, and Audi maintained an open-cockpit design philosophy until 2011, when the R18 TDI was unveiled with a closed cockpit. The R8 dominated the LMP900 class from its introduction in 2000, scoring 63 victories from 79 races. Weight and air restrictor penalties steadily reduced its advantage: by the 2005 24 Hours of Le Mans the R8 was required to carry 50 kg (110 lb) extra ballast and ran smaller air restrictors. The 2005 Le Mans Endurance Series finale at Istanbul marked the end of the R8's European racing activities. The R10 carried over the R8's carbon fibre monocoque and aluminium honeycomb, with the plastic bodywork replaced by a carbon-fibre composite construction to handle the increased weight of the V12 engine. Like the R8, the R10 was designed for serviceability: not only the rear bodywork but also the front crash structure were removable.
Audi was not the first to campaign a diesel at Le Mans. French brothers Jean and Jacques Delettrez entered the 1949 24 Hours of Le Mans with a car bodied by Delage powered by a 4.4 L inline-6 producing 70 PS (51 kW), retiring after completing 1,660 km after running the starter motor battery dry. After a valve failure in 1951, the Delettrez brothers were the last diesel entrants until privateers Taurus Sports Racing entered a Lola B2K/10 powered by a 4,921 cc V10 TDI from a Volkswagen Touareg at the 2004 24 Hours of Le Mans. The first diesel race-car victory was a BMW 320d winning the 1998 24 Hours of Nürburgring.
The concept for a diesel-powered Audi prototype originated in January 2002 when Ulrich Baretsky, head of Engine Technology at Audi Sport, met with Automobile Club de l'Ouest officials Daniel Poissoneaux and Daniel Perdrix in Ingolstadt. Baretsky observed that 50% of European cars were diesel-powered and proposed the idea to Wolfgang Hatz, head of Engine Development at Audi. Hatz supported it, citing the potential for technology transfer — such as FSI technology already used in the R8 LMP's engines — between motorsport and road cars. Wolfgang Ullrich, head of Audi Motorsport, saw additional value in introducing Audi's diesel range to the United States market and in challenging the "dirty oil-burner" stereotype of diesel engines. Then-chairman Martin Winterkorn said at the car's Paris presentation: "The Le Mans project will help our technicians to extract even more from TDI technology." At the 2004 24 Hours of Le Mans, Baretsky met with Ferdinand Piëch, then-chairman of the Volkswagen supervisory board, who gave the project formal approval.
The engine block presented a unique challenge. Head of Audi Diesel Engine Development Richard Bauder suggested cast iron, as used in Audi's road diesel engines, but Baretsky rejected this on weight grounds in favour of an aluminium-silicon alloy block. Wolfgang Appel, director of Vehicle Technology at Audi, compared the task to the Apollo program. The Bosch Motronic MS14 ECU was bespoke — Bosch had not previously written software for an engine of this power. A Bosch common rail fuel injection system with piezoelectric injectors delivered fuel at over 1,600 bar (23,206 psi); combined with a Garrett turbocharger on each bank (limited to 2.94 bar / 42.6 psi), the engine produced over 650 PS (478 kW; 641 hp) between 3,000 and 5,000 rpm and 1,100 N·m (811 lb·ft) of torque. By the time of the December 2005 unveiling the engine had completed around 1,000 hours on the dyno.
Dow Automotive developed a specialised diesel particulate filter (DPF) consisting of a chemically treated ceramic honeycomb with high porosity and reduced weight. The filters were so efficient that exhaust was practically transparent and around 5 dB quieter than the R8 at 105 dB. Allan McNish noted that above 161 km/h the sound of wind was louder than the engine, making downshifting by ear difficult. The DPFs were mounted at the end of the exhaust pipes, which somewhat disturbed the weight distribution. After the 2006 race, Baretsky reportedly wiped the inside of the No. 8's exhaust pipes in parc fermé; team director of Joest Racing Ralf Jüttner noted the napkins were "as pristine-white as before."
The engine's high torque meant a 5-speed gearbox sufficed in place of the R8's 6-speed. Xtrac supplied a 5-speed pneumatically-actuated sequential unit with a ZF Sachs ceramic clutch; Megaline supplied the gearbox control system. Despite far superior torque, the new gearbox was lighter than the R8's, being a thin-walled aluminium casting versus the R8's Ricardo magnesium case. Bosch supplied the Acceleration Slip Regulation unit. The R10's fuel efficiency was among the highest of any racing engine of its era: 41.05 L/100 km (5.73 mpg-US) at the 2006 Le Mans and 45.56 L/100 km (5.16 mpg-US) in 2008, compared with approximately 75 L/100 km (3.14 mpg-US) for a 2007 Formula One car.
Joest Racing handled the R10's Le Mans campaign while Champion Racing partnered at Sebring. The R10 replaced the R8 in the American Le Mans Series following Sebring and was not reintroduced until the fifth round, the 2006 Utah Grand Prix. Joest used Sebring as a testing ground for Le Mans preparations.
At the 2006 24 Hours of Le Mans, piezoelectric injector problems emerged during qualifying. To manage the issue, Audi limited how far each engine ran in qualifying. Despite this, Rinaldo Capello put the No. 7 R10 on pole with a 3:30.466; the sister No. 8 qualified alongside with Marco Werner setting a 3:30.584, over 2 seconds faster than the nearest petrol-hybrid Pescarolo-Judd C60s. In the race the No. 7 lost twenty minutes in the fourth hour replacing an injector, then suffered turbo failure, effectively eliminating it from overall contention. The No. 8 ran cleanly, with only an unscheduled stop for a gear cluster change. The No. 8 took the overall win, covering a record 380 laps at 215.4 km/h (133.8 mph), four laps ahead of the No. 17 Pescarolo-Judd; the No. 7 finished third. Tom Kristensen set the fastest lap at 3:31.211 and the record for longest LMP1 stint, covering 16 laps on a single 90 L tank. Emanuele Pirro extended his consecutive podium finishes to eight. The R10's victory was the first for a diesel in a major event since a Cummins Special qualified on pole at the 1953 Indianapolis 500, and the first diesel win at Le Mans outright.
Following the Le Mans win, the R10 appeared in the UK for an exhibition at the 2006 Goodwood Festival of Speed, where McNish raced the car against a Harrier Jump Jet over a standing-start 1 km stretch at RAF Wittering. The R10 was first to reach 241 km/h (150 mph) before the Harrier overtook it and became airborne.
Champion Racing assumed the R10's ALMS campaign as Audi Sport North America. Frank Biela and Emanuele Pirro drove the No. 1 R10, with McNish and Capello in the No. 2. Capello broke the Sebring lap record in pre-season testing with a 1:47.308. At Sebring, the No. 2 led every lap to give Kristensen a then-record fourth overall win at the event, before suffering cooling problems. Audi won all remaining rounds to become the first manufacturer to win every LMP1 race of an American Le Mans Series season.
Minor refinements were made for 2007: lighter particulate filters, more precise suspension, an improved Bosch ECU, and revised Michelin tyres. The power band was improved for driveability and fuel economy. Lucas Luhr and Mike Rockenfeller joined from Porsche.
Audi entered three cars at the 75th 24 Hours of Le Mans, all run by Joest Racing. The No. 1 was driven by Biela, Pirro, and Werner; the No. 2 by Capello, McNish, and Kristensen; the No. 3 by Luhr, Alexandre Prémat, and Rockenfeller. Kristensen had suffered a severe crash at the opening round of the 2007 DTM season in April and was replaced for test days by Mattias Ekström, who swapped to the No. 3 to match his stature with the No. 2 crew. After Kristensen was cleared to race following a test at Brands Hatch, Ekström returned to Sweden.
The No. 8 Peugeot 908 HDi FAP of Sébastien Bourdais, Pedro Lamy, and Stephane Sarrazin topped testing with a 3:26.707, over a second and a half quicker than the second-placed R10. Sarrazin took provisional pole in dry qualifying with a 3:26.344; wet conditions the following day left this time unbeaten, giving the No. 8 Peugeot pole. The No. 2 R10 of Capello, McNish, and Kristensen lined up alongside on the front row.
Bourdais led but ran wide on the first lap at the Dunlop chicane, handing the lead to Capello. Rockenfeller crashed the No. 3 into an Armco barrier near Tertre Rouge in the opening hours, destroying the rear assembly; after attempting to repair it, he retired. In the seventh hour a safety car was deployed after Werner's No. 1 R10 made contact with Jan Magnussen's Chevrolet Corvette C6.R. An improperly fastened wheel nut from a pit stop caused Capello's left rear wheel to detach, sending him into the barriers at the Indianapolis curve; Capello was uninjured but retired. The No. 1 R10, with Pirro now leading, held a four-lap advantage over the second-placed No. 7 Peugeot 908 HDi FAP of Marc Gené. Rain fell in the final hours; Werner, now driving the No. 1, ran wide at the Mulsanne Straight chicane but suffered no damage. Biela took the chequered flag, giving Audi a fourth consecutive Le Mans win: 5,029 km (3,125 mi) at 209.15 km/h (129.96 mph), achieved despite more than two and a half hours under the safety car. The R10 also recorded the highest top speed since the Jaguar XJR9 at 351 km/h (218 mph), compared to the XJR9's 389 km/h (242 mph) at the 1989 24 Hours of Le Mans. Pirro extended his consecutive podium finishes to nine.
Audi entered the Le Mans Series for the first time in 2008, with Joest Racing fielding two cars against Peugeot's two-car entry. Peugeot won the first three races of the season before Le Mans. At the 2008 24 Hours of Le Mans, the No. 2 R10 of Capello, McNish, and Kristensen took the win on lap 381, beating the No. 7 Peugeot by just over four minutes. The Peugeot 908 HDi FAP qualified in the 3:18 range while Audi struggled to get below 3:23; in the race the Peugeot was up to 3.5 seconds a lap faster, but superior Audi pit work and the R10's advantage in wet conditions secured the win. Peugeot won the final Le Mans Series round at the Nürburgring; a win by Capello and McNish at Silverstone gave Audi the Constructors Championship, while Mike Rockenfeller and Alexandre Prémat earned the Drivers and Teams Championships in the No. 2. In the ALMS, Porsche ended Audi's seven-race Sebring winning streak; Audi rebounded with wins in the next two events. Allan McNish overtook Christian Klien in the Peugeot on the penultimate lap to win Petit Le Mans.
In 2009 Audi replaced the R10 with the R15 TDI for factory efforts. Colin Kolles announced that his privately entered R10s would contest the 2009 24 Hours of Le Mans with factory servicing assistance. The R10 best finished 7th overall, a few laps behind the highest petrol finisher, a Lola-Aston Martin in 4th. In 2010 Kolles fielded two R10s in their final Le Mans appearance; unlike the factory diesel LMP1 cars these were not subject to the new restrictor regulations that removed approximately 60 bhp from diesel prototypes. Both cars qualified at 3:30 but failed to finish due to gearbox strain from torque loading.
The 380 laps completed by the R10 at the 2006 Le Mans set a new record for laps completed, though it did not surpass the distance record set by Helmut Marko and Gijs van Lennep at the 1971 24 Hours of Le Mans; that record was later broken by the R10's successor, the R15. Together with the R8, the R10 remains one of Audi's most successful Le Mans prototypes, entering 48 races and winning 36. The R10 won the 2006 Autosport Pioneering and Innovation Award, presented by Jean Alesi and Eddie Jordan to Wolfgang Ullrich. Regulatory changes by the ACO prior to the 2011 season closed out Audi's open-cockpit lineage: turbodiesel engine capacity was reduced from 5.5 L (335.6 cu in) to 3.7 L (225.8 cu in), and fuel tank capacity from 81 L (21.4 US gal) to 63 L (16.6 US gal). In a 2014 Motor Sport magazine special, Capello described the R10's front fascia as "the most beautiful front end we had in the last 10 years at Audi Sport."
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