Stock 360 that LIKES 93 octane?

[RED-85-Z51]

Gas station was out of low and mid the other day so I filled up the wag with 93octane and WOW the thing has come alive.

Idles smoother, starts easier hot and cold, runs a little cooler it seems, and overall the engine feels just a hair smoother when running.

I know all about how high test gas is for high compression engines, for controlling spark knock. I havent detected any spark knock on this thing, but again I have no idea where it's timed...

But wow this engine hasnt run this smooth since Ive had it...in fact Ill say it is the best idling, smoothest revving Carbed engine Ive ever driven.

For the small increase in fuel cost per fill up, Im not opposed to using 93...but it's odd that a low compression engine would run better with high octane fuel...

Maybe the low grade has more alky?

[jaber]

I have been told by several engine builders that the older engines run better on the higher octane fuel and have always run that or mid when money was a little tight.

[RED-85-Z51]

I had a 1967 Thunderbird with the 390Big Block that was sporting some impressive compression, around 10.75:1 as I recall and that thing absolutely could not be run on anything under 93. If I put in low it would nearly ping at idle.

That engine ran best on 93octane + a full can of "outlaw" octane booster...got expensive though. I think I was only getting 7-8mph tops out of that car with the 3spd C6 trans.

[rixcj]

Last week,I put 89 octane (vs. 87 octane) in my jeep, for the first time. I don't know why, just a compulsion, I guess.

It does seem to run better.

Perhaps I'll try 93 octane, next time.

Rich

[JeepNOFEAR]

I only use 93, if I use 87 then the jeep sputters and runs rough. I also get better mpg. There is also a local gas station that sells 100% gasoline, no ethonal, and that helps also.

[yankeedog]

mine doesnt like that bilge water either

[fsjman1978]

When I bought my 74 the previous owner told me he ran nothing but 92 or higher. I have tryed to stick with that. I tryed to run 89 once when gas prices were over $4.00 a gallon but ran really rough and sputtered alot.

[Serious Johnson]

If it runs better on higher octane, then it was pinging before, whether you could hear it or not. Lots of things can cause that -- spark timing, egr malfunction, high operating temperature...

S.J.

[KyooMac]

The gas station next to my shop sells racing fuel, in the winter I fill my 82 waggy with half race/ half 89. I know it's overkill, but it works great when it's cold.

[bushwood44]

You could back off the timming and run low grade but would lose a little power.

[RED-85-Z51]

Another point. After my drive to work, the last 8 minutes of which is 65mph straight, I pull into work and park, Id have ot idle for a minute otherwise the engine would want to diesel.

not on 93, shuts right off clean after pulling off the highway and parkingm not even a hint of wanting to run-on.

[Ghinmi]

Mine runs the same on 87, 93, or 110. I've made passes back to back with 87 vs 110 it runs nearly identical times either way.

On the other hand, my bone stock '86 Monte runs like junk and gets bad mileage with 87 and I actually save $$ on gas by running 93.

[Charlie_B]

If a motor is tuned correctly for a certain octane and everything is in good working order, putting higher octane in shouldnt make a difference. If it does, it was pinging before the higher octane fuel was added. The "desieling" comment justifies that theory IMHO.

Like stated above, run a little less timing, and I bet you dont see the difference in between grades of gas. Unless you dont mind paying a little more for gas.

This is all assuming that you are comparing different grades from the same supplier. Some stations use the same supplier, but some are much different around my area.

I usually try to tune on a lower grade gas than I would run normally. That way you factor in a slight margin of safety for those hotter/colder days or get a batch of bad gas.

my .02