E39 M5 Dyno Battle: 409k Miles v. 78k Miles
Does mileage really affect horsepower long-term? The E39 M5’s S62 V8 is more resilient than you think.
If you recall from a couple of months ago, we made a post about the highest mileage E39 M5 in the country and possibly the world. Being one of the best sports sedans of its era and possibly of all time, we are happy it is still alive. Obviously, the centerpiece of this stunning car is the engine. The S62 V8 was silky smooth and produced a stunning 400 HP with very little displacement for its time. However, we do not see these cars on the road often. Most are plagued by maintenance issues and folks just don’t want to put up with fixing a 20-year-old BMW.
However, this one guy had a completely different idea. With that in mind, he managed to keep his M5 well past the 400,000-mile mark. This car was then purchased by YouTuber Alex Palmeri, for a measly $8,000 USD. He then decidedly drove the car back home to his hometown 12 hours away and survived. We have to be honest, we think that was impressive to start. However, Palmeri is far from done with the car, he now has brought it up against another E39 M5 to answer the age-old question. Does mileage affect engine performance over time? Thanks to LegitStreetCars on YouTube, we get to find out.
To start, it is important to note that the M5 that Palmeri will be going up against is a “garage queen” with only 78k miles. However, when they dynoed this car, it only managed to make 207 WHP. This means there was something terribly wrong with this M5. After some substantial diagnosis and tuning, this M5 managed to make an additional 100 or so WHP. This is right around the stock power level it should be making. According to the BMW master-tech who was running the dyno, a healthy S62 should make around 310 WHP on this particular dyno.
For comparison sake, it is safe to state that Palmeri’s engine was replaced and only bears 320k miles, while the other M5 is on the original engine. Palmeri also has an aftermarket ECU tune as well as a muffler and cat delete. However, for the comparison, both cars ran the stock tune. For the first run, Palmeri managed 282 WHP. There were some issues with making power in the higher rpm that the tuner attempts to solve. However, the second and third runs see even more loss of power.
What happens when they throw the ECU tune back on though? 325 WHP instantly on the first run. Tunes do actually work, folks! The other M5 with the same tune managed a healthy 346 WHP. Thus, there is only a 20 WHP loss between these two specific cars even though they have 240,000 miles in gap. We have to say that is damn impressive. So as long as there are no outstanding issues with your S62, you should be making the same power for decades.
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