Fuel Grade

[MyFirstHonda]

What fuel grade are you running in your Si? 91 is recommended but 87 is acceptable.

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[Two Step Performance]

We recommend 93/91, whatever the best available is. If you are considering power modifications, you will find premium is required.

 

[TypeRD]

I always run the recommended fuel grade. Pinching a couple of dimes at the pump (to fill up on a grade that is lower than the manufacturer’s recommendation) is a risk that could cost you more money down the road in repairs. At the end of the day, you only end up paying $2 or $3 dollars more to fill up the tank. It’s part of the cost of owning a fun, performance vehicle versus a boring econobox.

 

[Dopenutz]

Run 91 minimum. Ive seen what 87 does to these engines with time and they usually fail prematurely and thats on stock power.

 

[V3N0M_VZL4]

here 93, please do not cheap gasoline this will cost you more in repairs, check the gas lid or the owners manual for more details

 

[MyFirstHonda]

here 93, please do not cheap gasoline this will cost you more in repairs, check the gas lid or the owners manual for more details

I checked the gas lid before I made the post. Either grade is acceptable. Just curious what everyone else uses.

 

[CivicR38]

I'd never just put 87 in a turbo charged car.....just not worth it in the long run. A full fill with 93 costs me like 30 bucks, an extra 10 bucks a week to preserve the engine and performance....worth it....

 

[NoelPR]

For those that say: "But but the ECU is programmed to retard ignition to allow lower grade fuel"

Let me tell you something.

When you realize that knocks need to occur in order for the ECU to dial back timing then you will understand that using the recommended grade is the way to go.

 

[Integra23]

I like to cut my fuel with water to save money and I figure it performs similar to adding a meth kit.

 

[ayau]

For those that say: "But but the ECU is programmed to retard ignition to allow lower grade fuel"

Let me tell you something.

When you realize that knocks need to occur in order for the ECU to dial back timing then you will understand that using the recommended grade is the way to go.

eh kind of. Modern knock strategy will pull timing across the entire load range and will stay that way for an indefinite period until higher octane is put in. It’s not like it’s constantly retarding it only after it detects knock.

 

[TypeRD]

I think the point is to use the recommended fuel grade whenever possible. Sure, one can choose to use the minimum fuel grade (safely) in a pinch. Not all filling stations carry 91+ octane, so it’s a nice convenience feature that the ECU can adjust for lower octane.

For instance, the owner’s manual for my ‘09 Si said to use 91+ octane or risk engine damage. There were times I pulled into the filling station only to have to get right back in my car and search for 91+ octane. It wasn’t a big deal and didn’t happen often, but it definitely would’ve been nice to be able to put 87 or 89 in it (on those rare occasions) and be on my way.

 

[MyFirstHonda]

I think the point is to use the recommended fuel grade whenever possible. Sure, one can choose to use the minimum fuel grade (safely) in a pinch.

I agree.

 

[NoelPR]

eh kind of. Modern knock strategy will pull timing across the entire load range and will stay that way for an indefinite period until higher octane is put in. It’s not like it’s constantly retarding it only after it detects knock.

And how it knows it has higher octane fuel?

There isn’t such thing as octane sensor.

The ECU has to keep testing by advancing timing and listening. In other words you are exposing the engine to unnecessary knocks all the time by using lower grade fuel.

 

[ayau]

And how it knows it has higher octane fuel?

There isn’t such thing as octane sensor.

The ECU has to keep testing by advancing timing and listening. In other words you are exposing the engine to unnecessary knocks all the time by using lower grade fuel.

nobody knows the actual knock strategy unless you're a honda engineer that works on the ecu knock strategy. we're just all speculating how often the ecu attempts to advance the timing. for all we know, the ignition may need a restart after it has detected the first knock before it starts advancing again. the best you can do is log the ecu knock sensor and make some assumptions on the knock strategy algorithm.

the fact that honda has stated minimum is 87 means their ecu strategy accounts for the 87, and there won't be longterm negative effects.

i'm not suggesting you should put 87 only. just stating that these engines aren't going to blow up if an owner only puts 87.

on the other hand, if the owners manual stated that putting 87 would potentially damage the engine, then that's a different story. i believe the STI manual said something along those lines if i remember correctly.

 

[aspitfyr]

Factory, 91+.
If you’re tuned, follow the tune guidelines.

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