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FYI Premium in R18's

28018 Views 86 Replies 54 Participants Last post by  FD7683
I am not trying to stir up the nest here, but I do want to share. I have been on the Honda Forums since 2006. With the 8th Gen Ridgeline, CRV, 8th Gen Civics and Si, and the 8th Gen Accord. There are literally thousands of posts on Fuel use. Will be considering seriously trading my 09 Coupe for the CRZ early next year.

I did try to switch to 93 on the Ridge with no perceived difference in performance or mpg's. I also did try 87 on my two 06 Si's and had a definite perception of deteriorated performance (no knocks though). I tried 93 on my two 08 Accord V6, again with no perceived changes or mpg's.

Now, I have switched to 93 on both my 09 Civic EX-L coupe and my 2010 Civic EX-L Sedan the last two tanks. I can truthfully say: I perceived a smoother running engine, lesser press on the accelerator to reach my normal speeds, I gained 1-2 more mpg, and very happy overall with the improvement in performance of both vehicles. Worth the extra two bucks for a tank of gas.

I've read most arguments, Pro and Cons, of switching grade of fuel. I am not claiming anything one way or the other. I only want to share this. The Honda manuals on all the above vehicles (except the Si's) does say "recommend 87 Octane OR HIGHER". I understand that to mean, "at minimum, use 87 Octane fuel" I am never satisfied with "minimums". But, that's just me.
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In the FA5 I ran 93

But in anything elses I drive 89 does the job. In my brothers 91 Civic Si we found a 5 MPG gain using 89 than using anything else
I found a bump in mpg and a bit more smoothness by running 89 in my LX
wow, you can't even get 93 in CA . . . well, at least not commonly.

I've ran 91 in the R18 before and noted better mileage, I've also ran it with a good amount of octane boost that probably put it at 93+, haha. seems to get me better mileage, but idk, I havent really done it enough to know for sure.
I run 95RON on an R18 and get around 28 mpg

I think my engine was badly broken in :(
Many many years ago I put Sunoco 98 Octane in my Prelude Si (which was in mint condition mechanically). I am fully aware of octane ratings and compression, so in theory it should have done nothing or made it worse. It ran like a bat out of hell on the stuff. I paid a whopping $3 !THREE DOLLARS! per gallon for it back then. If Sunoco still offers 98 and 104 octane gasoline, I will give it a try. I am no chemist, but from that experience, I assume there are some more variables to fuel than just octane rating. My new civic LX is the first car I have owned since 1996 that does not require premium gas so I will explore this more in time. Back then (97ish) I lived in Colorado and the fuel there was watered down with something or other "it is greener fuel" type of thing. It did something to the octane rating where regular was 84 and premium was 90, but cost a lot more. All I noticed was I used more of it. When driving back to Maryland and hitting up a gas station in Kansas with normal fuel, I felt an instant boost of power (so it could not have been coming down from a higher altitude/thin air because I was already down in the plains before I refueled).
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Yeah I ran premium 93 in my LX today
and it was def smoother acceleration......

Would anyone like to dyno? lol
I've been running 93pump in my auto R18 for over 10,000 miles now and it has been much better since using 87. The car runs smoother and still gets great gas mileage when i'm not reving it out in every gear ;) haha
I'm going to dyno it sometime in november with my fujita cai, p2r tbs and si axleback. wish me luck.
Moved to Civic Coupe & Sedan
On my 08 lx coupe, i ran 93 only... With only a few tanks of 87 to test it out, mpg went down rpms went up and te motor was more hesitant too.

Now my 10 lx sedan ran only regular and it was noticeably slower then my coupe.

I remember a dyno test showing the r18 motor had some knocks with 87, and a 10.5 compression ration is pretty high. They say the motor can get away with 87 because of the oil squirters cooling things down.

With that said if you can afford premium, use it. :shrug:
I've been running 93pump in my auto R18 for over 10,000 miles now and it has been much better since using 87. The car runs smoother and still gets great gas mileage when i'm not reving it out in every gear ;) haha
I'm going to dyno it sometime in november with my fujita cai, p2r tbs and si axleback. wish me luck.
Good luck man post up ASAP! lol
I did try to switch to 93 on the Ridge with no perceived difference in performance or mpg's. I also did try 87 on my two 06 Si's and had a definite perception of deteriorated performance (no knocks though). I tried 93 on my two 08 Accord V6, again with no perceived changes or mpg's.

Now, I have switched to 93 on both my 09 Civic EX-L coupe and my 2010 Civic EX-L Sedan the last two tanks. I can truthfully say: I perceived a smoother running engine, lesser press on the accelerator to reach my normal speeds, I gained 1-2 more mpg, and very happy overall with the improvement in performance of both vehicles. Worth the extra two bucks for a tank of gas.
Well, yeah of course using gas with a lower than recommended octane rating will hurt performance.

As for a a higher than recommended octane giving smoother running and better MPG, I call BS. Some newer engines can detect a higher octane fuel and adjust the spark timing to be more aggressive, but even then the difference is pretty much imperceptible.

Other factors like temperature and humidity are much more likely to cause changes in your engine's performance and your MPGs.
^^ agree.

The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites.

What is difference in the fuel grades, is the amount additives in the fuel. For example the premium will have more fuel additives than the regular grade gas. Also depends on where do you get your gas?

Back to the octane thing. So really if you guys are putting a higher octane in your r18, you are really just wasting money and actually possibly polluting more, by not fully igniting all the fuel in the cylinder.

But 10.5 is alot higher than older civics, id would try the mid grade gas and see if you can get the same results.

Also a note shell and now chevron/texaco i believe use the same amount additives across the fuel grades.

And for the guy with the older civic, and older cars in general, People will find their old cars run better on premium gas, b/c they have gunk build up and the compression has risen in the cylinders.
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Yay someone brought some sense to this thread!
What about the knock that was reported on the dyno test?
What about the knock that was reported on the dyno test?
:yeahthat:
I wanna know what this is about..
What about the knock that was reported on the dyno test?
What dyno test? Link?
On a hot humid day going from cheap brand gas to higher quality higher octane gas will probably make a difference. The key is combustion chamber temprature. Oil injectors cool down the piston to a degree and that's impressive on a budget car. But combustion chamber temps can get hot- hot day and even more so for those with short ram "cold" intakes which such in hot air. Also load on engine. Full throttle at low rpm really heat up an engine. It's better to run higher rpms which allow for tons more air to be sucked in. Most lawnmowers work on this principle - set throttle to wide open or it will bog down and over heat.

I vary what I buy based on weather and my guess on how heavy my foot will be.
My R18 used to drive alot better with 91 octane fuel.
With the 87 octane it pinged at times, mostly in the hot summer weather.

I just used regular gas to save money however, its just a civic.
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