NOW FOR THE BENCH RACING
(Or My Professional Analysis, however you want to look at it)
The M3’s tires were in fact a year and a half old, while the Mustang had new tires. Even though we used the same tires, differing ages can greatly affect their performance, even if the tread isn’t worn down. This is why most magazine tests are often highly erroneous and useless since many of them compare cars with tires of varying ages, at differing times of the day, and some magazines even use different drivers! Anyone who tracks their car knows that lap times can vary by over a second from the early morning to the heat of the afternoon and even more so when you introduce variables of the drivers testing the cars.
The proper way to test and compare cars is to practice on an old set of tires, then mount a new set for the comparison test. Every tire has a couple laps of ‘magic’ before they fall off a noteworthy amount and remain fairly consistent for most of their life. MotorTrend’s Best Drivers Car competition with Randy Pobst has the best test procedure of any other magazine competition.
Since we are aware of this, we tried to eliminate as many of these variables as possible. We used the same driver on the same day, and went a step further with the same tire, despite the M3 having older tires. To take this into account, we had data from when the M3s tires were brand new on a day with similar weather conditions and were able to overlay and compare them. Compared to the new tire baseline run, the M3’s lost just over half a second from cornering. Taking the difference in tire into consideration, our M3 on brand new stickers would have turned a 1:33.2 to 1:33.3, still about 0.3 seconds slower than the Mustang GT. Now the Performance Package with its larger brakes and a 3.73 final drive (from the sluggish 3.31 of our base Mustang) will make the Mustang noticeably faster. Probably in the order of half a second or more. The GT350 would be a couple seconds faster yet and the GT350R a few more seconds on top of that.
At the end of the day, from this analysis, our 465hp M3 turned essentially the same lap time as a base 2016 Mustang GT. Both cars generate nearly identical lateral cornering Gs, minimum cornering speeds, and are almost identical in a straight line for accelerating and braking. Today the Mustang won by nearly 9 tenths of a second, but with proper analysis and comparisons of similar tire conditions, we know that you can throw a blanket over either of them.
With improper testing due to ignorance of the impact of weather and tire degradation, we could have introduced another second of difference if we ran the Mustang at 9am and the M3 at 3pm in the heat of the day. Unfortunately this is how some magazines operate and thus their results should be taken with a grain of salt.