[Matt]

Both dealers I went to didn't have any info on this. I imagine it's going to be something like "We recommend premium, but unleaded can be used."

Anyone got any info?

 

[1chrisb]

I know what you mean, but premium(91+ octane) IS unleaded. All gasoline on the mass market is unleaded. You can run regular(89 octane) just fine, at the expense of some power.

 

[Baron164]

To get the full 252hp you need to use 93 octane, 87 octane will give you 243hp, either fuel will work in the car as it will adjust. But to get the most out of the vehicle you'll need to use premium.

Edit - From Manual:
Configuration Transverse mounted I4, cast
aluminum cylinder block and
cylinder heads
Bore x Stroke 87.5 mm bore x 83.1 mm stroke
(3.44 in. x 3.27 in.)
Displacement 1999 cubic centimeters
(122 cubic inches)
Compression ratio 9.3:1
Horsepower 252 hp @ 5500 rpm on 93 octane
243 hp @ 5500 rpm on 87 octane
Torque 270 lb-ft @ 2500 rpm on 93 octane
270 lb-ft @ 2500 rpm on 87 octane
Redline 6500 rpm continuous
6800 rpm 3 second over-rev
Specific output 126 hp/liter
Valvetrain Twin independent variable cam
timing
Ignition Coil-on-plug
Fuel system 150 bar fuel pump
Throttle body 57 mm (2.2 in.)
Pistons Cast aluminum
Crankshaft Cast iron
Connecting rods Forged steel
Turbo Single scroll / 21 psi max boost*
Exhaust system 63 mm (2.5 in.) diameter
* SAE Certified Performance ratings are achieved with 19.5 psi, but up
to 21 psi can be delivered to maximize power depending on fuel quality
and atmospheric conditions.

 

[faST]

To get the full 252hp you need to use 91 octane, 87 octane will give you 242hp, either fuel will work in the car as it will adjust. But to get the most out of the vehicle you'll need to use premium.

Power numbers were made on 93 octane. From the manual:

252 hp @ 5500 rpm on 93 octane
243 hp @ 5500 rpm on 87 octane

 

[goslice]

Not to split hairs but I thought I read in the supplement that using non premium fuel would reduce HP to 243. The interesting part for me was that there was no change to torque. Also, I wonder if using non premium fuel affects the over boost in any way.

 

[ATX Eric]

Just use 91/93. Cost savings are negligible over 87 or 89 over the course of a year.

+ power!!

 

[Baron164]

Well I was close

 

[higgrit]

Just use 91/93. Cost savings are negligible over 87 or 89 over the course of a year.

+ power!!

Precisely. Just to do a quick calculation. Lets say your tank is 12 gallons, and you fill up once a week using 87 octane. For the year to buy 89 will be ~$74 more a year and 91/93 would be ~$124. If you gotta pinch pennies just don't buy another pair of pants and there is your extra money for premium gas

EDIT: Personally I'll run 89 for the most part just going to work and what have you. But anything else premium it is.

 

[Ken Bury]

I wonder if the map will auto adjust to handle 100 octane. The stuff costs twice as much as regular but it's available here at a few places.

 

[ATX Eric]

I wonder if the map will auto adjust to handle 100 octane. The stuff costs twice as much as regular but it's available here at a few places.

Would love to know myself. We keep some 108 laying 'round here. Would be fun to find out what a tank feels like...

 

[Chip]

So i would imagine that if one want to put mid grade in, the hp will be roughly 247 hp. Still not to shabby. I average 8 gallons on a fill up. with gas runing last time i filled up @ 4.01 with 87 octane, came to $32.08. Running 91 would cost 33.68. i dont think an extra $1.60 to $2 is going to break the bank. But it is good to know that if someone had to run regular they could get away with it.

 

[Matt]

Good info guys. And thanks to the person who moved this to the right spot.

 

[oaxa]

I wonder if the map will auto adjust to handle 100 octane. The stuff costs twice as much as regular but it's available here at a few places.

I know the knock sensor pulls timing for lower octanes, I don't think it advances it for higher octane.

 

[cuda6pak]

I'll be running 87 pretty much all the time. A 10hp loss and zero torque is pointless for the extra $.30-.50 per gallon that premium costs over it. I'll throw 93 in there if I'm going for a specific drive through the mountains really pushing it, but for 95% of my DD'ing it will just be a quick run from 1st to 3rd every now and then.

 

[Neverlift]

I wonder if the map will auto adjust to handle 100 octane. The stuff costs twice as much as regular but it's available here at a few places.

You would have a higher effective octane from running a light mix of e85/ regular unleaded 87.... 30/70 or so is about 110 octane w/ DI. You will be able to increase timing manually with a tune. The ECU will not do it for you.

 

[agr964]

Not to split hairs but I thought I read in the supplement that using non premium fuel would reduce HP to 243. The interesting part for me was that there was no change to torque. Also, I wonder if using non premium fuel affects the over boost in any way.

If there is a peak horsepower reduction from running lower octane fuel there MUST also be a torque reduction if peak horsepower is found at the same RPM, which I would imagine it is:

252 HP @ 5500 RPM, yields 241 ft-lbs w/ 93 unleaded
243 HP @ 5500 RPM, yields 232 ft-lbs w/ 87 unleaded

Since: Torque (ft-lbs) = HP / RPM * 5252

About a 4% reduction in torque (at peak power anyway). The torque and resulting howsepower loss may be less (or non-existent) at lower RPMs, but we can't know until more data points or curves are provided.

 

[86azms3]

I would put leaded in it...will give mad power.

 

[86azms3]

I'll be running 87 pretty much all the time. A 10hp loss and zero torque is pointless for the extra $.30-.50 per gallon that premium costs over it. I'll throw 93 in there if I'm going for a specific drive through the mountains really pushing it, but for 95% of my DD'ing it will just be a quick run from 1st to 3rd every now and then.

You should buy a civic or accord or something. Will be a better match for you.

 

[86azms3]

I know the knock sensor pulls timing for lower octanes, I don't think it advances it for higher octane.

Very true. There are plenty of timing maps on an ECU for various circumstances...but all those circumstances timing is being pulled.

You would obviously have to tune to reap the benefits of higher octane unless you are already knocking.

 

[Matt]

I'll be running 87 pretty much all the time. A 10hp loss and zero torque is pointless for the extra $.30-.50 per gallon that premium costs over it. I'll throw 93 in there if I'm going for a specific drive through the mountains really pushing it, but for 95% of my DD'ing it will just be a quick run from 1st to 3rd every now and then.

That's along the lines of what just crept in my mind. I'm thinking 87 during the snowy months, 93 on the weekends, and 87 during the weekday commute.

Is it bad for my engine or fuel system or anything like that to switch constantly like that?