91 vs 94

[Gruber]

https://fueleconomy.gov/feg/bymodel/2020_Honda_Civic.shtml

you are welcome

And what is this supposed to be and related to what? As I said above, EPA calculates mileage and cost of gas based on the fuel that is recommended by the manufacturer. For some civics Honda recommends premium fuel.
Keep looking.

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[Gruber]

Here's a Car and Driver article where they compared regular to premium.
https://www.caranddriver.com/features/a28565486/honda-cr-v-vs-bmw-m5-ford-f-150-dodge-charger/

It does make wonder if a vehicle's computer can adjust timing & boost in both negative & positive directions. If the system can adjust for lower octane can it also adjust for higher octane, within reason? I don't know how tightly the octane number is controlled. If it varies +/- 1%, does a vehicle's computer make adjustments in either direction in order to optimize fuel economy, emissions, or power?

If 91 octane is used in a basic 1.5L Civic will the computer increase the boost in order to help optimize efficiency? If so, it's probably so small it's not worth the cost of using premium gasoline, but is there any boost gain at all?

Well, that's the point that I'm making. If hatchback sports ere indeed tuned identically to non-sport, but premium fuel gives them a power bonus, than you can't at the same time say that regular 1.5t doesn't get any bonus from premium. Yet some people do say it. You can't have it both ways. Or rather it has to work both ways.

The car can't measure or sense fuel octane any other way than by monitoring the knock sensor, misfires and maybe some other data. The only way the PCM can adjust timing is to retard it until all these data are in range, and then keep trying to advance it, until something starts to go out of limits.

So at any time the car is running the PCM is constantly trying to advance timing until it gives an undesirable sensor response. That's how it finds optimal timing continuously, just as the wideband O2 sensor keeps finding the optimal fuel flow continuously.

So of course it will increase the boost. Actually it will not so much increase the boost, as it will refrain from limiting the boost as it may have been forced to do on regular gas, when reacting to increasing knock events.

 

[mega_milk]

Why does Honda say use premium on sport instead of going by the engine?

Both 2.0 and 1.5 come in sport and non-sport models.

If the engines are the same, why would the model with sport require premium? Why would premium be required in a sport 2.0, but not the non-sport 1.5? Doesn't make sense.

 

[zspeed]

Why does Honda say use premium on sport instead of going by the engine?

Both 2.0 and 1.5 come in sport and non-sport models.

If the engines are the same, why would the model with sport require premium? Why would premium be required in a sport 2.0, but not the non-sport 1.5? Doesn't make sense.

Because it is the “SPORT” model.

 

[Gruber]

Why does Honda say use premium on sport instead of going by the engine?

Both 2.0 and 1.5 come in sport and non-sport models.

If the engines are the same, why would the model with sport require premium? Why would premium be required in a sport 2.0, but not the non-sport 1.5? Doesn't make sense.

Honda does not recommend premium for the 2.0 N/A Sport sedan models which are specified to the exact same max hp as non-sport. Only for the 1.5T Sport models, which are hatchbacks, specified to a bit higher max hp.

 

[jakdotdot]

Accordingly, no text or review, or car description or specification in the entire internet ever classified any civic as a premium-required car.

Not him, but..

Required Fuel - Premium Unleaded

pulled from,

https://owners.honda.com/vehicles/information/2006/Civic-Si-Coupe/specs

 

[Vic_L]

Why does Honda say use premium on sport instead of going by the engine?

Both 2.0 and 1.5 come in sport and non-sport models.

If the engines are the same, why would the model with sport require premium? Why would premium be required in a sport 2.0, but not the non-sport 1.5? Doesn't make sense.

The 2.0L 'Sport' trim level found on the Civic Sedan / Coupe is not the same 'Sport' trim found in the Hatchback. It is literally a "sport" aesthetic with the Sedan / Coupe models.

Canadian spec Civic Sedans (as an example):

Compared to the Hatchbacks:

EDIT: Similar in the US it looks like (with additional in-between trims)
Civic Sedan by the way.

 

[mega_milk]

Thanks for the responses. The LX hatch still has the same engine with the same boost pressure. Do you think it has a way different tune and can't take advantage of premium gas? I think there is a little bit of marketing going on because premium gas is more expensive.

If I had a hatch I would definitely try premium in it to see how it feels. It might help with the fuel dilution as well.

 

[Gruber]

Not him, but..

Required Fuel - Premium Unleaded

pulled from,

https://owners.honda.com/vehicles/information/2006/Civic-Si-Coupe/specs

Yeah, that's a 2006 Si. I meant current civics, where manufacturer's recommendations are unclear to some people. Here Honda and everybody else clearly says premium required.

 

[BriteBlue]

I'm glad my 1.5L is designed for 87 octane. By me Mobil is $2.24 regular & $3.12 premium. FWIW Mobil is the cheapest regular (other than Costco) & is the same price as non-TopTier gasoline. Costco TopTier is $2.19 reg & $2.85 prem.

 

[Vic_L]

Thanks for the responses. The LX hatch still has the same engine with the same boost pressure. Do you think it has a way different tune and can't take advantage of premium gas? I think there is a little bit of marketing going on because premium gas is more expensive.

If I had a hatch I would definitely try premium in it to see how it feels. It might help with the fuel dilution as well.

That's actually a good question.
I think the engine would be the same, but the ECU tune/flash is different, and the different exhaust system (?)

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