Hi, Before I start - I note immediately that I am not imagining things. I have a 4cyl 2005 Honda Accord Auto. I recently posted how I changed oil to 10W-40 (Castrol Syntec) due to the fact that I got some for free and that I was worried about using this thick oil in an engine that recommends 5W-20. Ok, here is the thing; the engine "pulls" much faster and better with 10-40. Also, it shifts into the next gear slightly "later" with this oil making the car feel faster of the mark. I drove a friend's Accord with 5W-20 back to back (also 05 4 cyl) and difference is amasing. Any comments? I do intend to switch to 5-30 after the next oil change or even back to 5-20 but I just might put 10W-30 (instead of 10-40). Comments?