For some reason Asobo coded FUEL to use FPS / GPU cycles as an internal timer. It seems its performance was coded / optimized using 60 FPS. If you have a modern graphics card that's hoofing out 250+ FPS, you'll notice odd stuff, like mystery trucks skating down the road super-fast, teleporting, etc ... some vehicles will perform amazingly crappy (eg: Barracuda truck due to delayed turn-response and recovery).
When you cap the FPS back down to 60, all of this resolves itself. Suddenly mystery trucks, dopplers, and mavericks obey speed limits. Vehicles have great response times (Barracuda's turn response/delay is great, and a viable vehicle to use now), etc, etc.
Coding a game to rely on some arbitrary timer the computer controls is a classic problem that's been plauging gaming since the 80's (when old games were programmed to use CPU cycles as timers... and then CPU's got faster so those old games go bonkers with screens moving so fast you can't do anything).
"How do I fix this?" Edit
Basically, FUEL needs it's FPS capped. You can do that easily by turning on Vsync (Vertical Sync) which will cap FPS to your monitor's refresh rate.
Oh, right ... FUEL doesn't have a Vsync option built into it. *sigh*
To work around that, you're going to have to open your graphics card's control panel, and find a way to switch on Vsync for FUEL. Maybe there's a global FPS limiter built into your gfx card's control panel. Nvidia's Control Panel lets you setup a global profile for games, then lets you pick from a list of software installed to tweak override profiles per game. In that, I just selected FUEL from the drop down, and turned both Vsync and Triple Buffering on (Triple Buffering makes Vsync work better... at least according to Nvidia's cheat sheet popup text when I moused over the option).
My monitor has a refresh rate of 60hz, so Vsync capping FPS to that means FUEL will be limited to 60 FPS. I know some monitors these days have higher refresh rates. Using Bandicam's built-in FPS limiter and playing around, it seems on up to 100 FPS allows things to still perform half-way decent. So, if you have a monitor with like a 90+ refresh rate (do they make such a thing?) then Vsync'ing that should still be ok.
Going over 100 FPS will start to see performance degradation in FUEL. The sweet spot seems to be ~60FPS (or maybe it's just FUEL's FPS capped to your monitor's refresh rate ... this needs more testing).
Overall, a lower FPS seems to do FUEL better (which sounds stupid in our age of wanting to push for greater FPS). If you have a program that can limit FPS, you can mess around to find the sweet spot you like. By messing around with Bandicam's, I noticed screen tearing with 60 FPS (without Vsync on). 90 FPS was decent. But, overall, just turning Vsync on resolved all of this. (For me, anyways. Your mileage may vary.)