I use antutu and when I first started running benchmarks it was in the 21k range. After a while it started to run in the 26l to 32k range. I believe one reason is due to using a different browser and running clean master before hand. I get the same behavior when running with a cooled down phone also did that on my f6.
after running antutu on g2 clean master notified me that the phone needed to cool down for five minutes. this is after I rooted, installed overclock kernel and used stweaks to control cpu. set at 2.7 ghz and keep at least two cores running. phone now scores over 35k, about 100 pts behind the htc one m8. stweaks also has adjustments and advice on settings concerning overheating and battery drain.
after running antutu on g2 clean master notified me that the phone needed to cool down for five minutes. this is after I rooted, installed overclock kernel and used stweaks to control cpu. set at 2.7 ghz and keep at least two cores running. phone now scores over 35k, about 100 pts behind the htc one m8. stweaks also has adjustments and advice on settings concerning overheating and battery drain.