I just signed a new lease on a new Civic hatchback Sport Touring.

[jayy_swish]

Yeah, I went ahead and did some research once I had a minute. Sue me for not looking this up since I started driving... Just going off what everyone has told me for my entire life.

Higher octane provides more compression. More power if your engine / map can handle it. Mostly has to do with knock. Doesn't matter much day to day for our cars. However, if the manual and gas cap both recommend premium, why would you not? At that point it Honda is telling you they have designed the car to be run on 91 or better (Sport, ST, CTR). So even though I may have been off in terms of benefits, I would think we should probably use our cars how Honda designed them right?

My remaining question, though, is how does it affect the leftovers. Like the teensy tiny amounts that don't combust, and build up on your engine over time. Wouldn't this be *ever so slightly* reduced if the gas is compressing more and therefore combusting more, providing more force inside the cylinder?

Well Honda designed these cars to run on 87 stock (minus the Si and type r), but they do include fuel maps for higher octane fuels... hence premium fuel recommended. Most people buy Honda’s for 2 reasons. Cheap and reliable. That’s why they’re optimized to run on 87 to keep ownership costs low and the yearly fuel costs on the sticker when you first buy the car low (the fuel sticker that tells you how much you’d save annually). That being said I use premium fuel because I am tuned and now run a E40 blend now also.

The left over gets slipped past the piston rings and into the crankcase mixing with oil on the cylinder walls and creates blow by, which is why I recommend oil catch cans as they filter that out. Stock systems take that blow by and route it back into the intake to be re-burned the next combustion cycle and that’s what gunks engines, but this happens with all fuel grades not just lower grades fuel. All the fuels have the same amount of energy, it’s the advanced timing that adds the horsepower not the fuel itself. Premiums fuel’s benefit is that it allows the engine to do advance timing because of its higher resistance to pre-ignition. So it all burns the same regardless of 87, 89, 91/93 it’s just a matter of what time is the spark plug going to spark to ignite the air/fuel mix. As the image shows the left is what would happen with premium fuel 91/93 octane, the right is what happens with a lower grade fuel 87 or 89 octane. Both burn the same it’s just a matter of timing.

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[disgraced.fk8]

Well Honda designed these cars to run on 87 stock (minus the Si and type r), but they do include fuel maps for higher octane fuels... hence premium fuel recommended. Most people buy Honda’s for 2 reasons. Cheap and reliable. That’s why they’re optimized to run on 87 to keep ownership costs low and the yearly fuel costs on the sticker when you first buy the car low (the fuel sticker that tells you how much you’d save annually). That being said I use premium fuel because I am tuned and now run a E40 blend now also.

The left over gets slipped past the piston rings and into the crankcase mixing with oil on the cylinder walls and creates blow by, which is why I recommend oil catch cans as they filter that out. Stock systems take that blow by and route it back into the intake to be re-burned the next combustion cycle and that’s what gunks engines, but this happens with all fuel grades not just lower grades fuel. All the fuels have the same amount of energy, it’s the advanced timing that adds the horsepower not the fuel itself. Premiums fuel’s benefit is that it allows the engine to do advance timing because of its higher resistance to pre-ignition. So it all burns the same regardless of 87, 89, 91/93 it’s just a matter of what time is the spark plug going to spark to ignite the air/fuel mix. As the image shows the left is what would happen with premium fuel 91/93 octane, the right is what happens with a lower grade fuel 87 or 89 octane. Both burn the same it’s just a matter of timing.

I appreciate you not being an ass about this to me after having every right to. Honestly, I had something happen at work that really had me fired up and still was when I wrote that reply. Definitely was not thinking clearly. Then I looked back and was like wow, that was 100% uncalled for... However; this is not an acceptable reason, so I do sincerely apologize. Not cool on my part. You're just trying to drop some knowledge on a fool.

Lots of good info beyond what I know, and I definitely appreciate it. Never thought about the connection between the "estimated savings" and the fuel trim either... I just knew it'd be way better on gas than my Crown Victoria I do have a pretty solid understanding of octane rating now though which is nice, so I don't look like an idiot next time too!

It's funny though, I find it hard to call these 10th gens "cheap" just because they're so damn well built. I had a normal Sport before the Sport Touring and it was still extremely nice. Now with the Touring, with the ivory leather seats, people tell me it seems like it seems like a Lexus or an Audi. Actually the cop thought it was a Lexus during an accident report! For me, I guess I think in terms of longevity with Hondas. And obviously reliable! Especially Civics and Accords, those things run forever even when you mistreat them. We treat these babies right, we're looking at an easy 200-300k miles if you ask me.