Ok, just kidding, oil does matter, but for a Honda J-Series Engine, it really doesn't matter what you use within reason as long as you change it at 6-7500 miles and take care of the car. I present my 220k under valve cover pics. Looking back at my maintenance log I've used: Mobil1 5W30 10W30 5W20 0W20 Penz Plat 5W20 Valvoline MaxLife 5W20 5W30 Milesyn SRX5W20 - Current Oil Filters Supertech ST3950 ST3593A Bosch 3323 STP2808 Purolator L10193 and PL10193 Wix 51334 And my current Partsmaster 61334 The only oil I did not like was Mobil 'Supersyn' Which I ran 1 time and the car developed a leak. I have no clue why, but I swapped it back out for Penz Platinum and the leak went away. I had the covers off to do the first valve adjustment the car has seen. All the exhausts were tight and all the intakes were loose as you'd expect, but there was still a bit of play on the exhausts (the ones you'd worry about) so they still probably weren't in danger of doing something they shouldn't have. Car still runs like a champ and will get 30+mpg on the highway if you drive it like a sane person, granted, these days I just use it for my 12 mile commute. Take care of your machine and they will take care of you.