What octane fuel do you use?

Snax · Post by **Snax** » Fri Aug 24, 2007 9:59 pm

I'm a newb and noticed in the Road & Track review at the intro of these cars that they cited the recommended fuel as 91 octane. That seems unnecessary to me, so what's the real world on this with a good running motor?

I'm tempted to split the difference on my first fill with 89.

neonsport · Post by **neonsport** » Fri Aug 24, 2007 10:37 pm

The engine in my Tercel runs great, but every 3AC I've had (7 or 8 ) has pinged like crazy off the line if I don't run premium or feather it off the line. While I'm a conservative driver, I don't like having to do all the management with my ears and right foot.

brianp · Post by **brianp** » Sat Aug 25, 2007 7:43 am

I usually fill with Regular, unless the engine has been pinging alot recently.

shogun · Post by **shogun** » Sat Aug 25, 2007 12:56 pm

i use 95 octane, which is premium gas around here, but when i race i use 106 octane, te car feels great with that gas

Snax · Post by **Snax** » Sun Aug 26, 2007 9:32 am

I filled it with 89 and it seems to do just fine on it, so that's likely what I will stick with.

GTSSportCoupe · Post by **GTSSportCoupe** » Sun Aug 26, 2007 9:55 am

I've found it all depends on how you have your ignition timing set. 5 degrees advanced = gutless motor but 87 octane. 10 degrees advanced = more responsive motor but 89-91 octane. 15 degrees advanced = quite peppy compared to stock motor but 94 octane.

You pay for power...haha!

Typrus · Post by **Typrus** » Sun Aug 26, 2007 3:59 pm

89.
I had it timed (base) about 27 degrees advanced once... That was after I reset my cam timing to where it belonged and snugged the belt down past tension strength (old Toy tech gave me that trick) but didn't change the dist. Cam change=dizzy change.
It pinged like a monster off the line unless I feathered it... BUT GOOD GOD did it have power above 3500RPM... It was great! Best drive into town I ever had (fixed the timing once I got to school.. heh)

Around here its 85, 87, 91. All 10% Ethanol. (shrug) works for me.
Doesn't ping on 85, but it gets worse fuel economy. Worse enough to offset the cost. I'd imagine that if I advanced it some more and went premium I'd get another offset-type improvement.

I'm tempted to try an E85 conversion... We have a pump in Fort Collins and its currently $2.019/gallon for E85 compared to ~$2.799/gallon midgrade. Thing is I'd need a Weber 38/38 (you have to richen it up quite a bit for E85) or a beefy 32/36. Worse fuel economy is also a factor. Most people get 5-15% worse. Thats still from low-mid 30's to low-hi 20's. Though, a more than 50 cent/gallon savings would likely offset it. Problem would be I'd be confined to visiting cities within a tanks range and that had E85 pumps.

takza · Post by **takza** » Mon Aug 27, 2007 4:57 am

I use various kinds of 87 octane that have a good chance of containing ethanol. I use advanced ignit...can't say how advanced due to slightly loose pulley key. Get no ping above ~1500 rpm in 5th. Decent power. EGR doesn't work. Recently found O2 is not cycling...so no function there. Still get 32 mpg mixed though...last summer 33-34. Using ozone air bleed to compensate for the O2 lack. Use a Condensator which is supposed to reduce emissions/increase mpg. Use V-power plugs and have Valvoline Synpower additive in engine...plus moly in trans. After installing the Condensator...and after running some windshield washer fluid into the intake (slowly as in a few ounces each 100 miles) as a carbon cleaner...I see much less oil use.

Typrus · Post by **Typrus** » Mon Aug 27, 2007 10:31 am

How do you set up a water injection or water/meth injection?
"Steam-cleans" the rings out?

takza · Post by **takza** » Tue Aug 28, 2007 4:58 am

I just drilled a small hole in the 1/2" return line to the intake from the Condensator...with one of those plastic vac connxs stuck in the large tube...acts as a venturi and the vac pulls some...use a model airplane fuel valve...attached to a 20 oz or so glass jar. This way it has a foot or so to mix into the PCV flow.

I'd recommend that if anyone messes with water injection...that some MMOil or ATF or whatever be used as a top oil in the gas....cause if you don't watch closely...it's way too easy to let too much water in. The valve you use is critical...hard to find one that meters down as much as needed....then you can have issues with plugging or flow rate vs viscosity...water or wind fluid vs light oil.

Not sure that the windshield fluid is needed (contains methanol) ...water might do OK. I only ran maybe 20 oz or so of mostly windshield fluid thru this winter...must be the Condensator that keeps it clean?

Not sure clean rings = better mpg either...can't hurt?

Another method would be to make a good PCV jar and then use a dish soap bottle to slowly squirt maybe a pint or so of water into the carb to clean the rings.

Post by **Petros** » Tue Sep 04, 2007 10:19 pm

I use the highest octane pump gas I can find, but I am running about 11.2:1 CR and advanced timing. I did this, along with a few other tweaks to improve the power output. I ran regular (low octane) gas for a while at first, but burned valves and wasted several head gaskets. Since I get a little better MPG with the high test gas, my overall cost is about the same but w/o the head gasket issues.

Neu · Post by **Neu** » Wed Dec 12, 2007 3:39 pm

I use Shell V-Power, which is either 91 or 92, I can't remember. But right now it's a mixed tank, and it's running fine. Timing is advanced 5 degrees.