Back in the 1990s, Mobil 1 held an unusual endurance test to emphasize the importance of regular maintenance. The subject was a BMW 3 Series E30 with an M20 engine. After a break-in period of just over 1,000 miles on public roads, this 325 spent the next four years in a lab. It literally stayed there day and night.
When the test ended, the car had traveled an impressive 1,000,000.5 miles (1,609,344.8 kilometers). The 3 Series ran on Mobil 1’s Super Plus unleaded gasoline and used the company’s fully synthetic oil. The inline six-cylinder received an oil change every 7,500 miles (12,070 km) according to BMW’s recommended maintenance schedule.
The first 50,000 miles (80,467 km) were part of a durability cycle at a constant speed of 55 mph (89 km/h). The rest simulated highway driving, repeatedly going from 40 to 85 miles per hour (65 to 137 km/h) and back again until the odometer reached one million miles. During the four-year test, Mobil 1 closely followed BMW’s maintenance requirements.
Finally, the 2.5 liter naturally aspirated engine was removed and subjected to a thorough inspection. The six-cylinder was found to be in near perfect condition with minimal signs of wear. Despite the seven-digit mileage, most components were still within factory tolerances.
Whether the result proves the durability of the M20, the fluids of Mobil 1, or a combination of both is up for debate. One could argue that a million miles on a “treadmill” is not the same as driving in the real world in different weather and road conditions. Heat cycles also take their toll on engines, but that wasn’t the case here as the car was only stopped for maintenance.
Still, it was a fascinating long-term experiment and an effective marketing measure. It also highlights the value of regular maintenance. Fast forward to 2025, and the 35-year-old BMW 325is is still going strong, now with a new owner who will hopefully add even more miles to an already well-used car.
