jayy_swish
Senior Member
- First Name
- Jay
- Joined
- Mar 10, 2020
- Threads
- 18
- Messages
- 1,291
- Reaction score
- 890
- Location
- Los Angeles
- Vehicle(s)
- 2019 Honda Civic Sport Touring
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.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?
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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