I second pennywern's opinion. MEX (E20) or Elite (E6) highways can be a mess sometimes. My advice is to check traffic conditions before you take Grab. 10AM should be fine leaving KUL but I'd rather take train + cab. 28 mins from KUL T1 to KL Sentral plus a cab ride to your hotel. Grab is a bit harder to find or it'll be really expensive if you arrive KL Sentral between 1630 and 1930 weekdays (especially if it's raining) tho but you aren't arriving at those time.