Filled up 1st time with HPR(Full Tank) in my 2007 f250 6.0. I noticed it running smoother and idling quieter later in the day once the diesel got flushed thru with HPR. Next day starting was so much smoother and quieter just on a cold start. I do notice a small gain in power and real light smell from exhaust compared to the overwhelming smell from D2. still cant confirm MPG gains as my driving is sometimes aggressive, but overall i like this fuel.