Fuel for Civic VX

[GasSavers_BIBI]

The question is mostly for VX owner, but in same time to everyone.

I do run Supreme fuel in my VX since I own it (91-92 octane). Where I live, there are lost of hill to climb and since I don't want to downshift, I put supreme fuel so the car run better (especially at low rpm because VX does run often below 2000rpm). Also, since I'm crussing 60mph (100km/h) on highway, I'm telling myself that I have a better FE with supreme fuel.

I would like to have your thoughts on this.

[jadziasman]

This might not be a great idea for two reasons:

1) Premium costs more - sometimes much more than regular 87 octane. Kind of defeats the purpose of buying a car that gets good fuel economy.

2) Higher octane fuel is more difficult to ignite than regular gas and it is formulated to be more uniform - it contains fewer volatile components that burn at lower temperatures. High performance engines run hotter than econoboxes so it is more critical for the high output engines burn gasoline that won't pre-ignite or detonate. So, if you decide to drive your VX like someone delivering pizzas in 10 minutes or less, you might need premium. If you drive like your grandma (that's my driving style) you don't get any benefit from premium at all. That's the short answer.

My VX's have not run on anything but 87 octane except when my current VX's engine was overheating due to a clogged radiator. I put in mid grade 89 octane just in case the engine was reaching the point of irregular combustion with the 87. I did not need to use 89 octane for more than one tank full and only as a precaution - I replaced that radiator quickly! No blown head gaskets for me thanks.

[GasSavers_BIBI]

Sold, no more SUPREME in the VX, I wonder if my MPG will suffer, don't really think, will tell, but since I don't plan to use my car for the next week, will wait.

[thisisntjared]

whats the compression of the vx motor again? you understand what higher octane does right?

EDIT: nevermind I am glad you understand now.

[GasSavers_BIBI]

Not 100%, its give a better detonation, and ?

[jadziasman]

D15Z1 (VX) 9.3 to 1.

D16Z6 (EX) 9.2 to 1.

Both are VTEC. Not high compression as you can see.

[thisisntjared]

the compression is my point. it does not make the higher octane fuels volatile enough to make the best use of higher octane fuel. jadziasman gave the perfect explanation before i responded

only motors with higher compression (or forced induction) can really make the best use of a higheroctane.

[GasSavers_BIBI]

My arguments (that I gave to myself...) was that when I was accelering at 1700-1800 rpm to climb a hill, it was better for the motor with high otcane fuel, and I thought I had a greater MPG to, but I never REALLY do any test. By swithing to 87 octane, I will see if the last arguments stand or not, I doubt it tho. Thanks for the fast reply.

[Sigifrith]

I plan on running a tankful of Shell Premium thru my VX. I've read that it contains 10% more of chemicals to clean the engine. After that, it's back to the cheap stuff.

[Rick Rae]

Originally Posted by Sigifrith

I plan on running a tankful of Shell Premium thru my VX. I've read that it contains 10% more of chemicals to clean the engine. After that, it's back to the cheap stuff.

For what it's worth, I'm in the middle of a very informal "experiment" on that at this very moment. If you glean any useful data please consider sharing it!

Rick