Ultra 94
 

ok so my car has seen only 87 octane all its life.....my buddy was telling me how he switched to ultra 94 and that it makes a world of a difference and he gets much better milege...... is this fact tru, i know in my manual it also says to use premium gas on a d15b2 lol...??? but anyways I dunno.....what you guys think???

the difference between price per mileage isn't worth it for you unless you have an engine the needs it! With gas prices right now, stick to 87-89. If you want to clean it a bit add some red line gas treatment from crappy tire or some lucas fuel additive.

on that 89 hatch it will do more harm than good

Use what the owner's manual suggests. Don't use 91 or 94 if it only needs 87. Higher octane level is needed to prevent detonation which leads to knocking. Correct me if I am wrong.

over and over again i have read in automotive mags, manuals, guides etc. that a higher octane fuel doesnt do anything beyond what is required. waste of money imo.

its all about your butt dyno..lol

Yes, the higher octane fuel doesn't detonate as easily as lower grade does. The higher octane is necessary in engines that get much hotter than a 1.5L would. If you put 87 into say a Porsche, just the heat in the cylinders would be enough to detonate the air/fuel as it gets compressed, that's where your knocking comes into play

it's heat that causes pre-detonation? I thought it was the compression more then the heat that causes it(or the heat caused by compression ^^)

Attachment 39620

from my 91 civic sedan manual. and if you dont believe me

Attachment 39621

lol would love to hear why that is.

the motor that comes in the sedan and the in the dx hatchback are the same, 1.5l 92hp 10:1 compression ratio, so 91 octane would make sense, I doubt 94 would make any diff to 91, but 94 to 87 would be a decent jump

it does say research octain. which has been discussed many time on honda tech. one guy didnt believe my manual said this thats what the second picture was about. and iv been told even though my manual says this its not true. i dont use 91 that often anymore because of the price.. but iv found i get better mpg with it.

Canadian gas pumps are rated using the Anti-Knock Index which is RON+MON/2. Out of the two tests, RON is easier and generates higher Octane numbers. Your manual indicates 91 RON which would translate into 87 AKI octane.

it takes longer to ignite the AF mixture. Can leave a ton of un-burnt fuel. If you dont know why that's bad, then go research.

higher compression causes more heat..

the D15B2 only has 9.2:1 compression ratio, so 87 will do more than enough

i had the 88 hatch DX for the winter and it does have a little difference for putting 87 and 94 ( i have tried many times), but neither gives more gas mileage thou. i still avg 500km per 40L of gas

right now i am on DOHC ZC in my EG hatch and i still drive the same way i did with the EF, but i get 600km per 37L of gas

the ZC requires 95 RON which is equals to 91 octane here, so 91 RON for D15 will be 87 octane

you sure that 89 has that motor :P? msn autos lists it at 10:1

good info. but iv always got better mpg with 91 on a 3.5h 401 trip.

i had the same engine and of coz i know~

if the compression is 10:1 then it won't be only 92hp

msn autos also says the 1.5L 92hp (97ftlb???????) I4 is mpfi. so i dont think there talking about a d15b2 there.

http://autos.msn.com/research/vip/sp...da&model=Civic

wow some awesome info, thanks guys!

but yeah i knew about the detonation and all and how higher octane minimizes detonation. So then i realized that because this engine is so weak, a higher octane gas would only make things worse because it would put more stress on trying to ignite...correct??