GM Once Tried To Make Diesel Look Cool With A 94 MPG Sports Car That Weighed Less Than A Lotus

General Motors hasn’t always had the best relationship with diesel cars. Back in the 1970s, diesel cars were seen as slow, clattery, smoky, and in the case of GM’s cars, hilariously unreliable. By the 2000s, General Motors wanted to showcase that diesels didn’t suck anymore and it needed a vehicle to prove it. In 2002, GM proved that diesel could be cool by putting a 94 MPG diesel into its mid-engine, Lotus-derived Opel Speedster sports car, then used it to take speed records.

One of the hardest hurdles the world’s automakers have had to leap over is proving that diesel power could do more than just power working vehicles. For most of automotive history, diesel has been the go-to choice for the makers and operators of heavy machinery from high-capacity pickup trucks to warships. Diesel engines are known for making gobs of power at low rotational speeds, sometimes nearly bulletproof reliability, and for fuel consumption that cannot be matched by gasoline engines in the same configurations.

This is why the mighty General Electric diesel-electric locomotives thundering down the rails in your hometown don’t have massive gasoline prime movers, but maybe something like a 188.5-liter, 4,400 HP V12 diesel. It’s also why the big glistening Peterbilt Model 589 going down the Interstate has a 14.9-liter Cummins X15 straight-six. When it comes to moving heavy loads efficiently over very long distances, diesel still wins.

However, for a time, much of the world saw diesel as more than just a hard worker. Many saw diesel as the future of internal combustion. In the 1970s, diesel was seen as a cheat code to the multiple oil crises and economic crunch. But many of the diesels back then were slow, unreliable, and unrefined. The only reason you bought one was to save money. However, after the emergencies passed, automakers continued their development of diesel engines, and they got better with each generation.

By the 1990s and the 2000s, a new future began to open up for diesels. Continued development resulted in diesels that got substantially better fuel economy than their gasoline counterparts, but now they were also refined enough that people were starting to pick up regular passenger cars powered by the engines. By the 2000s, some diesels were so good that you might not have been able to tell a vehicle was a diesel without looking at a badge or tachometer.

There was another element to this as well. The promises of a greener fuel seemed tantalizing. Investments in biodiesel skyrocketed in the early 2000s, and if you were an alternative fuel enthusiast, you might have even heard about running diesels on waste oils. Remember, this was also a time when hybrids were coming into their own and when some automakers briefly got really serious about building modern electric vehicles.

While America didn’t catch the diesel bug like Europe did, everyone was seemingly interested in trying something different than just gasoline.

Over in Europe, governments were convinced that diesels were the greener future and helped spur both diesel development and adoption by sweetening the deal with subsidies and tax incentives that favored diesels. The result was shocking, as in the years right before the revelations of Dieselgate, diesel engines were a dominant force. Most new cars sold in Europe were diesel, with adoption rates as high as 80 percent in regions like France. In other words, diesel was just the default option out there.

Diesel became so infectious that it even spread to America, where about a quarter of Volkswagen of America’s sales were diesels, convincing other automakers to try to advance diesel cars here, too.

This didn’t come entirely out of nowhere. Automakers spent much of the 2000s working to convince the world that diesels were really cool. One effort from General Motors was the Opel Eco-Speedster, a car that set out to prove that diesel was so good it was befitting a sports car and a potential racecar. CarBuzz recently reminded me of this car, and I subsequently fell down a rabbit hole.

Proving Diesel Can Be Fun

The best source about the Opel Eco-Speedster is a 2002 article by Automotive Intelligence. I highly recommend clicking the link because it’s a time machine back to what the Internet looked like just after the turn of the millennium. It’s too perfect, from the cute fonts to the published images that are no larger than what we consider to be thumbnails today.

Anyway, in 2002, then-General Motors brand Opel wanted to kick off its own diesel push. In 2003, Opel and Vauxhall introduced a new 1.3-liter Ecotec common rail four-cylinder diesel engine. While Opel could have just gotten the wheels turning with a press release and a boring show car, it and General Motors decided to showcase just how far diesel engines had come by building what people might have thought was a rolling contradiction. The Opel Eco-Speedster was a mid-engine sports car that was nearly half the weight of a Mazda Miata and went blisteringly quick despite having a tiny diesel engine as motive power.

In 2002, Autoweek spoke with Walter Treser, who was then the director of advanced engineering in Russelsheim. Treser explained that Opel wanted to do something impressive with its new engine. However, they were entering territory already explored by other automakers. They thought about making a car with a top speed of 186 mph and with 78.3 mpg fuel economy. Well, one problem was that Volkswagen had already done the 78.3 mpg thing with its Lupo 3L TDI.

Opel also considered 124 mph and 117 mpg. The fuel economy figure was impressive, but nobody would care about a sports car with a top speed of only 124 mph. So, ultimately, Opel decided to split the difference. Its car would go 155 mph, which still was impressive for a diesel, and get 94 mpg, which is a really big flashy number.

The Better Elise

The vehicle for this effort was the Opel Speedster, the better-looking half-sister of the Lotus Elise. General Motors was looking for a way to improve Opel’s image with a spicy sports car. That’s when it noticed that Lotus, a brand it used to own, was quite popular. Lotus was already working on a successor to the highly successful Elise Series I and GM took a liking to the idea of having an Elise-like car of its own. The two companies struck a deal to develop the two cars in parallel.

Our very own Thomas wrote a great piece on the Speedster:

It’s common conjecture that the Opel Speedster and its British twin, the Vauxhall VX220, are basically Lotus Elises, but that’s only half-right. See, Motor Trend reported that out of the 2,000 parts that make up an Opel Speedster, only 140 were shared with the original Elise. Sure, the extruded and bonded aluminum construction is similar to that of the Elise, but a 1.1-inch wheelbase stretch is only the tip of the iceberg when it comes to changes.

The Speedster gained an airbag and anti-lock brakes, five-lug hubs and rear discs from a Saab 9-3, entirely new baby supercar coachwork with stacked exhaust tips and jewel-like lighting. The dashboard was new, the tires were new, the suspension tuning was unique, and while many of the Speedster’s changes were adopted by the series 2 Elise, compared to the original Elise, it may as well have been from a different planet.

However, the biggest difference is what came under the engine cover. While early Elise models came with the Rover K-series engine, not to be confused with the Honda K-series engine, that wasn’t exactly the most reliable motor in the world. In contrast, standard Opel Speedsters featured the 147-horsepower 2.2-liter Ecotec naturally aspirated four-cylinder engine from an Opel Astra, an engine that America got under the hood of the Chevrolet Cobalt, Pontiac Sunfire, Oldsmobile Alero, Saturn Vue, and a litany of other extraordinarily common GM models. This means that not only are engine parts absurdly cheap, you can get them from your local auto parts store no problem. Cheap oil filters, cheap spark plugs, the works. The Opel Speedster may look and feel exotic, but as far as regular maintenance goes, much of it is no more expensive than it would be on a Mazda Miata.

Crash Diet

The Speedster was the perfect car for Opel to set some records with. It already weighed just 2,215 pounds, and Opel’s team figured they could shave off hundreds of pounds more. But weight was only part of it. Opel’s International Technical Development Center ran some calculations and determined that if they were to hit 155 mph and 94 mpg using a tiny diesel engine, they had to cut the car’s drag coefficient in half.

Engineers first tackled the car’s frontal area. One easy way to cut down on frontal area is to drop the roof, and Opel engineers lowered the roof by 6.5 inches. This also resulted in the windshield getting a steep rake and the interior being nearly impossible to enter. Opel’s engineers gutted the interior to save on weight, leaving behind only a carbon fiber racing seat that was reclined back because there wasn’t enough room for it to stand straight up. Opel admitted that comfort wasn’t really a concern there.

Opel then fixed the ingress problem by throwing away the car’s standard door hinges for bombastic gullwing doors. Engineers also tossed out the car’s standard steering wheel for a removable racing wheel, again to aid in getting someone into that tiny cocoon of a cockpit. All of the extreme changes on the front end resulted in 12.5 percent less frontal area.

But that wasn’t enough. Now the team focused on reducing drag. For that, they extended the vehicle’s tail by 7.2 inches, which had the effect of making the air around the car less turbulent at speed. Engineers also smoothed out and lengthened the car’s body panels and equipped the concept car with smooth wheel covers. The idea was to make the car as long and as smooth as possible to reduce drag. The result? The Eco-Speedster had a coefficient of drag of just 0.20.

The final touch to the concept car was that all of these new panels were made out of super lightweight carbon fiber. The final weight was a remarkable 1,455 pounds (1,322 pounds in its final form). Of course, Opel then fitted its slimmed-down sports car with its newest diesel, from Automotive Intelligence:

This innovative engine is notable for its compact dimensions (length/width/height: 460/500/650 millimeters). In terms of fuel consumption, emissions and refinement it proves to be one of the best diesels of all. Compared with other current engines of similar output, fuel consumption will be down by approx. 10 percent and emissions will be cut by 30 to 40 percent and thus outperform the Euro 4 limits. At 1251 cc, this ECOTEC unit is the world’s smallest four-cylinder diesel, but with regard to output and torque it can compete with substantially larger engines.

The basis for this performance potential is the ultramodern design of the new 1.3 CDTI ECOTEC engine. An alloy cylinder head tops the weight-optimized cast-iron engine block (bore x stroke 69.6 x 82.0 millimeters). There are four valves per cylinder, operated by roller cam followers from two chain-driven overhead camshafts. The latest multi-jet direct injection system with fuel supply by ‘common rail’ at a pressure of 1600 bar is another noteworthy feature.

Fuel supply to the five-hole nozzles is controlled via an ultramodern solenoid valve. The fuel injection system’s response time is less than 20 millionths of a second, ensuring extremely fine metering of the fuel and up to five injections per working cycle. This not only keeps fuel consumption and exhaust emissions extremely low, but also ensures smooth, low-noise operation. Pilot injection helps to reduce the once-notorious diesel-engine knock in the warm-up phase to a hardly identifiable level.

Speedy Diesel

What did the Opel gang do with this car? They decided to set some records. This wasn’t too out of pocket for Opel. In 1972, Opel took a modified Opel GT “Diesel GT” with a 95 HP, 2.1-liter turbocharged diesel to a top speed of 122.7 mph. The car also broke records for speed and distance as it drove 6,213 miles (10,000 km) in just 52 hours at an average speed of 118.6 mph. That stunt generated headlines and put Opel on the map as a serious producer of diesel power. Opel then launched its first diesel car that year, the Rekord 2.1 D.

Opel describes the Eco-Speedster record run:

July 27, 2003 will also go down in Opel’s history as a special day. Because at exactly 12:44 p.m. the record drives with the Opel Eco Speedster on the high-speed track in Rodgau-Dudenhofen came to a successful end. The Eco Speedster set 17 international records for special cars with supercharged diesel engines within 24 hours.

The powertrain was trimmed for high performance for the record drives with the diesel prototype. Power was delivered by an 82 kW/112 hp version of the world’s smallest 1.3-litre four-cylinder diesel engine, which was also offered for the Opel Agila and Opel Corsa at the time (with 51 kW/70 hp). Opel engineers also explored the limits of technology with regard to aerodynamics and weight. The two-seat vehicle based on the production Speedster had a carbon fibre body, weighed in at only 600 kilogrammes and boasted a sensational drag coefficient of Cd = 0.20. The average speed of the Eco Speedster’s fastest lap during the 24 hours was an impressive 256.269 km/h. It reached a top speed of 256.739 km/h over one kilometre with a flying start. The swift Speedster also lived up to the “Eco” in its name: with consumption of 2.54 litres of diesel per 100 kilometres, it also put in a top performance.

That’s a top speed of 159.5 mph and a fuel economy of 94 mpg for our American readers. Other records set by the car include an average speed of 141 mph over 24 hours with an average fuel economy of 31.4 mpg. The best mpg observed during a specific fuel economy run was 111.2 mpg.

So, Opel’s engineers did it. They proved that diesel power was more than worthy of being called sporty. Keep in mind that this was also before Audi’s legendary R10 TDI effort.

It’s said that Opel built three of these experimental prototype cars. Sadly, these cars never went further than a demonstration of diesel technology and aerodynamics. Perhaps if Opel did more than marketing stunts with these cars, they might have been better remembered than they are. As for where these cars are today, it’s hard to tell. One of the three cars was listed for sale for $114,000 in Germany in 2019.

Honestly, this whole story is fascinating because it highlights just how much Europe was addicted to diesel engines. Multiple companies powered sports cars and racecars with powerful diesel engines. Diesel was so popular that the gasoline versions of some cars were the rare units to buy. It was also fascinating to see how quickly Europe dumped diesel after Dieselgate. But I’m still glad Opel did this, because the idea of a car that’s lighter than a Lotus, goes 155 mph, and gets 94 mpg still sounds astonishing.