I happened to be at a Honda dealership yesterday. I saw this chart which suggested 5W-20 for Accords 6th-generation onwards (previous generations to use 5W-30).

I was slightly taken aback cause I know the manuals for my 99 Accord asked for 5W-30 (or 10W-30). The parts guy said 30 would be too heavy an oil and I would lose some mileage, even though it wouldn't hurt the car mechanically.

Is that correct?

 

check out bobistheoilguy.com lots of discussions on this stuff, many people have differing opinions about it.... I personally usually run 10w-30

 

You might see a very slight gain going to 5W20 depending on your daily driving routine. 5W30 is just fine, stick with it if you've been using it. The 20 weight oils are excellent but if your car is running fine leave well enough alone.