Originally posted by Redcivic
Amen, mantis. I ran 87 octane in my old D16Z6 for 195k. Read your manual again, sure you can put 91-93 octane but 87 is just fine. Now some cars like my Maxima's for example, need a minimum of 90-91 octane. Ask my wife, she did'nt take my word for it and learned the hard way. She bought gas at a racetrack gas station because it was cheap. She filled up her SE with 87 octane and went back home. Later that day she went to the car, started it, and it died. It kept doing it. I was at it for two hours that night trying to figure out WTF was wrong and then finally she says, "well, I filled up with regular today because it was cheap, would that have hurt something?" So, I run to the zone and get some octane booster slap in there, and what do you know, she purrs like a kitten. But in general, most inline 4 honda motors can use 87 just fine for normal operation.
Compression ratios alone do not dictate which octane of gas to run, timing has also a lot to do with it. Stock timing curves for a D16Z6 are fairly aggressive, they also run very lean in the midrange RPMs in order to get good mileage (15.5 to 1 under light cruise). You can safely run a D16Z6 with regular and the timing bumped back a few degrees, but it's not going to run close to the way it can. I do agree that you should run the lowest octane gas that your car can handle without pinging - running premium in cars designed for regular usually carbons up the engine quite a bit.