volkswagens-for-life

My honda civic has 10.5:1 and is recommended to use 87 octane. Not to throw this off topic, but thats a hell of a lot of compression... especially for 87 octane. One would think there would be benefits to higher octane in such situations, no?

Tom400CFI

There is benefit to higher compression in any situation where you can manage it (not see detonation). More compression translates directly to more tq/displacement.

volkswagens-for-life

I'm sorry I mistyped; one would think there would be benefits to higher octane in such motors that have 10.5:1 but only require 87 octane, right?

Tom400CFI

Who knows? There are WAY too many variables to make a claim such as that. Combustion chamber design, quench, operating temp, cam timing, bore diameter, ignition timing....you can not say that such and such compression needs so and so octane. GM claimed the LT1 (due to it's very accurate timing control) could run 87 octane w/o losing any hp....an improvement over the (late) L98 which could not. The L98 could run low octane, but would have to cut timing to accommodate that fuel. Although the L98 had similar cam timing, same bore/stroke, and less compression, the tight timing control with the LT1 allowed for more compression on the same or even lower octane....as an example.

In general, late model motors may make a bit more power on higher octane fuel than lower, due to more available timing....but the difference would be imperceptible, SOTP. You'd only be able to measure any difference at a track or on a dyno. Any perceived difference would likely be the "placebo effect".

volkswagens-for-life

Way over my head But great information. Thank you Tom

856SPEED

What Tom is saying is there is static and dynamic compression . Dynamic takes into account for valve overlap from the type of camshaft (duration) and other factors while the engine is running rather than just static compression that we are familiar with when talking about compression ratios. There are a lot of variables as mentioned and the deciding factors of octane ratings revolve around cylinder pressure which creates heat in addition to the combustion process. Heat causes detonation.....so

86-Pace-Car

Thanks guys! I will forget about using octane booster.

Sassman

I use this stuff with every tank full. I'm not sure what it does, but my '94, which has no issues, runs noticeably smoother with it.

Tom400CFI

I love this stuff.


What it most likely does, is help you "feel good" about doing something to your car, and therefore you think it runs better. Sorry.

WW7

I knew this was coming.....But with Tom on this one ..Modern fuels have all the additives needed already built in , no need to add anything else unless you get moisture in your tank...WW

THE 383 admiral

It would be Nice if Ethanol was removed from all grades of fuel. Forcing 91 NON ethanol as a standard option.

84XfireAuto

I run only 93 octane in my '84.

If I cant afford 93, I shouldnt be driving a Vette. Thats my opinion at least.
And dont tell me it doesnt make a difference, I get a slight ping under heavy throttle with 87.
The car only needed 87 when new, but at 31 years old, all bets are off.

To the OP, stay away from those Octane Boosters. They are absolutely no good for your engine/fuel system.

whalepirot

I will add that my 406 was running 11.0:1, allowable, per the engine builder, due to the improved heat transfer due to the aluminum heads. I do know, despite my expected horrors, that the car ran just fine on 87 for the final leg of that trip, which included crossing the "Grapevine" on an extended drive. 87 was the only fuel pump working and I HAD to get refueled, but normally iI use 91.

Once, I used 110 racing gasoline.m The engine seemed smoother, but I felt no seat-of-the-pants change (back when $5/gallon was outrageous).

WW7

Your lucky, because (11 to 1) compression is suppose to be the upper limit for aluminum heads on pump gas...Usually anything over that and your likely to have to start mixing fuel.......WW

DGXR

Techron and Sta-Bil are very popular on CF. They are additives.

MavsAK

Sta-bil is garbage.
Techron has been proven to fix the C5s notorious fuel sending unit issues.

I'll run Techron, once in a while through my tank (usually 2 bottles at a time).

Most gasoline, that's name brand anyway aside from BP (for some reason the car runs rougher on that garbage), is good enough.

The only couple of additives that I can recommend is redline's fuel system cleaner, and techron. Anything else, is highly suspect at best. Especially things that claim to raise octane...because they don't. Not even 1 point.

Also what octane you run is dependent on a host of factors. My 89 says in the owners manual to run premium gasoline, when possible. (It also says to accelerate hard with the car every so often too. I'm serious it's right in there....were people that old fogey that they NEED that for advice?)

Even if you are running a car that says you can run 87 with no issues...that's if it's stock. For example if you've bumped the timing up...you've just raised your octane requirement too most likely etc.

You can run 87 in a C4 without problems, on relatively flat ground, and normal acceleration.... but it might not be up to par up hill, or in higher elevations for that matter.

I run 93 in mine, particularly when I'm stopping at an unknown supplier, gas station.

Tom400CFI

They may be popular...but that is proof of nothing. Wearing pants 1/2 way down one's *** has been a popular fashion trend lately...is that a worthy endorsement for wearing pants 1/2 way down our asses?

What does the product REALLY do? What are the products ingredients? What symptoms does our car have that requires the ingredients in the product?
^That makes sense.

"A lot of people use it" or "I use it and have never had a problem" -those are not reasons to pour elixirs of unknown content and purpose into various orifices of our cars. We don't follow that practice with our bodies (I hope)...why do that to your car?




A few of these products have real merit....but do we really need them? Do our bodies need 200% of our daily allowance of a vitamin? What do our cars, really need? BASIC MAINTENANCE AND CARE.

Tom400CFI

Higher elevation lowers the octane requirement.

PLRX

There is an octane booster out there called "TORCO", that crap has been used by many in the San Diego area. Many of them even took their cars to a dyno to find out "TORCO" didn't do a god-damned thing to their octane, performance or horsepower.

The only octane booster I've seen in person, test, and dynos that actually increase your performance is race gas. Race gas WILL NOT improve your MPG.

I've used 5gal of race gas/15 gal of 91 octane in The Ghost, and it helps a bit; 11.3:1 is just a bit different than a stock LT4.

MavsAK

Is that because the car's effectively running richer per stroke of combustion? (due to less air)

I thought it'd be the opposite, given that it takes more throttle to go a given speed.