Why is Blender 2.8 slower than older versions? I've been designing a car in blender, and getting a good image or animation takes hours. Then I heard 2.8 was out and that it cuts render times down significantly. So I installed it and I found that it was really slow, wireframe mode was buggy and the new engine, Eevee, was better but rendering was worse, nearly impossible.
Is the problem with 2.8 or maybe my computer. 
I've got a Mac mini, 2.3GHz Intel Core i5 with 8GB 1333MHz DDR3 RAM
My mate who has a Apple laptop has worse specs but can smoothly run it.
Eevee is used as a "quick preview" of sorts for your render. That way you don't have to wait for Cycles to sample before you can actually see your render in full detail; Eevee is real-time.

As for your main question, have you tried un-installing Blender altogether, and re-installing the latest version of 2.8? 

If you have, it might be that you have 8GB of RAM and an i5 CPU. These are not the best performance-wise.