Should I put premium gas in my 91 Honda Civic?

[SirGillroyJenkinstheThird]

Not a troll thread, my car's an older Civic and the manual says use premium gas. But I don't know if that's just some bullshit or what.

[sepht]

Does it have a turbo, high compression pistons, or a supercharger? If not you don't need high octane fuel for it to keep the engine from knocking.

[nutsack]

It probably pretty high compression. What engine do you have? Vtec?

It won't blow up using a fuel rated too low but the ecu will tweak the timing until there's no knock, leading to less power.

[Pabst]

If the manual says to use it, I would. If the ecu is set up for premium gas and you're putting in regular it won't run as well, and gas mileage will probably suffer also. Does it list an octane rating?

[The Cheshire Cat]

Unless you have a forced induction motor, there is no actual need to use anything over an 89 in your tank. Of course, this all varies from place to place. Some places carry a 85/89/91 while other are 87/89/93.... Best option for you, especially on such an older car is to run right in the middle.


I'll wait for someone else to mention burn types and combustion and all that other great stuff before I even attempt to jump in. By the way, if I followed the manual for EVERYTHING I'VE EVER DONE. I'd be missing a few fingers and there would be quite a few motors that didn't run right because of it.

[Pabst]

Originally Posted by The Cheshire Cat

Unless you have a forced induction motor, there is no actual need to use anything over an 89 in your tank.

That could not be more false.

[Gun Lover]

Originally Posted by The Cheshire Cat

Unless you have a forced induction motor, there is no actual need to use anything over an 89 in your tank.

No.

My N/A Honda with 11:1 compression knocks with anything other 92/93 octane.

[Pabst]

Originally Posted by Gun Lover

My N/A Honda with 11:1 compression knocks with anything other 92/93 octane.

+1 my mustang's compression is only 10:1 but I still have to run 93 or I get knock since the timing is upped.

[chilldo]

LOL no

[Vargus]

If the manual says to use premium, use it.

Really, it's not that big a deal anymore. 10 cents was a lot way back when but it's only like a buck or two more to fill up now. If your car is set up for it, you won't ping and you'll likely get another mile or two to the gallon.

And yes, it does affect fuel economy. Your ECM will see pinging going on with regular and will compensate by retarding your timing which reduces power. Ergo you need more gas to get where you are going.

[MediumD]

Originally Posted by Vargus

And yes, it does affect fuel economy. Your ECM will see pinging going on with regular and will compensate by retarding your timing which reduces power. Ergo you need more gas to get where you are going.

If you're WOT constantly, yes. Otherwise the effect isn't statistically significant..

Also, probably not on a 91 Civic. I don't even show it having a knock sensor.

[rider]

+1 on not having a knock sensor, I can't imagine that a '91 would use one. If you're that concerned about using a lower octane make a det can at home depot for 10 bucks and listen for det with lower octanes.

[The Cheshire Cat]

[SirGillroyJenkinstheThird]

Originally Posted by The Cheshire Cat

nooooo

[ArmsMerchant]

Originally Posted by Pabst

If the manual says to use it, I would

Amen.

[Vargus]

Originally Posted by MediumD

If you're WOT constantly, yes. Otherwise the effect isn't statistically significant..

Also, probably not on a 91 Civic. I don't even show it having a knock sensor.

Honda has done lean burns at cruising for quite some time. High octane will make sure things don't ping since the ECM clearly can't compensate.

[nutsack]

Depends on the engine. B16 was introduced around 1989 or something and definitely has a knock sensor, at least one variant of the D16 has one.

[MediumD]

Originally Posted by Vargus

Honda has done lean burns at cruising for quite some time. High octane will make sure things don't ping since the ECM clearly can't compensate.

Engine load at cruise should be low enough to not ping at almost any mixture I'd say.

If you wanna know, run it nice and low on gas and put 3/4 of a tank of regular. If it causes knock issues, pour a gallon of toluene in that tank and use premium from then on...

[Jive Talka]

From a complete car novice:

What are the differences between low/middle/premium and what effect, if any, would it have on a car?

[MediumD]

Originally Posted by Jive Talka

From a complete car novice:

What are the differences between low/middle/premium and what effect, if any, would it have on a car?

All cars suck in air, mix it with fuel, and squeeze it. Some squeeze it harder than others. Most cars squeeze the air to 1/9th (give or take 20%) the volume it started at. But squeezing it heats it up, and if squeezed too much, the mixture can explode before it's supposed to - it can explode when the piston it still trying to squeeze it. Which is bad. Higher octane fuels can resist exploding better than lower octane fuels, so the harder the engine squeezes the air/fuel mixture, the higher octane fuel it needs to avoid premature explosions.

[SirGillroyJenkinstheThird]

Man the answers here are so mixed.


Think I'll just use the middle grade.

[tibinstein]

Japan only has 100 RON fuel, use use 95 or 98 if you have a jap car.

[MediumD]

It doesn't really matter what Japan has. They made the vehicle to USDM specs to run on US available fuels. Speaking of which, we don't even have 95 or 98, because we use R+M/2 to rate knock resistance in our long chain organic aromatic hydrocarbon based fractional distillate fuels (since gas or petrol would be unacceptable to say.) Those would roughly convert to our ~89 and ~91 midgrade and premium ratings.

[nutsack]

Originally Posted by MediumD

our long chain organic aromatic hydrocarbon based fractional distillate fuels

[tibinstein]

Originally Posted by MediumD

It doesn't really matter what Japan has. They made the vehicle to USDM specs to run on US available fuels. Speaking of which, we don't even have 95 or 98, because we use R+M/2 to rate knock resistance in our long chain organic aromatic hydrocarbon based fractional distillate fuels (since gas or petrol would be unacceptable to say.) Those would roughly convert to our ~89 and ~91 midgrade and premium ratings.

I was thinking JDM import for some reason

[reggie_love]

I always fill up with premium. The price is not that big of a deal for me, especially in a city/state where gas is already expensive. It's worth the extra dollar or two to know that I'm not doing something contrary to the manual, subjecting my old yet sensitive engine to detonation, or running along with retarded timing.

On the other hand, I'm not a commuter. I think if I had a piece of shit economy car that I never drove aggressively but had to fill up frequently, I might downgrade to regular.

Plus (or whatever mid-grade is called where you're from) is usually the least economical at most gas stations. It can cost less to get half a tank of regular and half a tank of premium, though I don't know enough about fuels to say whether doing that is appropriate or produces a more favorable octane rating.