Octane and Compression

[gtxdude]

So we're taking the 65 Dart out West in Sept on Route 66, have a mild 318 with 9:2 compression (around there). I've been told that around New Mexico with elevation to switch to lower octane gas till California. Any thoughts on that? Have 600 Eddy on Performer intake. Thanks

 

[Dana67Dart]

I don't think that sounds right.


Regardless of altitude...
If the car does not ping on 85 octane ( just a number) but you put 90 octane (just a number) in it, the result will be that it will not ping.

Now on the other hand if the car doesn't ping on 90 octane (just a number) but you put 85 octane (just a number) in it the result will be that it might ping etc.


Now as for altitude, there is less oxygen in the air and a lower octane will not ping just as good as a higher octane at sea level.

I would just use the highest octane I can buy that does not ping. Heck if you could get 104 octane it would never ping regardless of altitude or load or temprature

 

[RustyRatRod]

Man some of yall like to worry. That's just somethin I wouldn't be concerned with until I got there.

 

[gtxdude]

Man some of yall like to worry. That's just somethin I wouldn't be concerned with until I got there.

Oh come on, I had nothing else to talk about

 

[RustyRatRod]

Oh come on, I had nothing else to talk about

lol I can relate.

 

[Bodyperson]

Oh come on, I had nothing else to talk about

You can lose power with too much octane. Runs too cool. Always cracks me up when the Dude says he blew up his lawn tractor cause he put racing fuel in it.

 

[oldmopardude]

your bigger issue is when you get to new mexico and Arizona, the fuel will be loaded with methanol. your engine wont like it much.

 

[65 Cuda 340]

Man some of yall like to worry. That's just somethin I wouldn't be concerned with until I got there.

Says the guy who spent a bunch of time trying to convert his slant six single point ignition to dual point.

 

[RustyRatRod]

Says the guy who spent a bunch of time trying to convert his slant six single point ignition to dual point.

Yeah well.......lol

 

[Phreakish]

It's not just less oxygen, it's less pressure.
Lower octane would probably be fine, but why risk a new variable on a road trip? Stick with what works.

 

[oldmopardude]

you will see a lot of 85 octane there as well,

 

[Dana67Dart]

My stock 67 dart 273 low compression runs fine on 85 "regular" here at 5100 feet

On the other hand my 2006 grand caravan 3.3L minivan pings on 85 but runs fine on 87.

 

[Dana67Dart]

BTW. You can get alcohol free gas. There is a website that listed the stations by city and state. It has made a world of hot summer drivability for my 67 dart.

Ethanol-free gas stations in the U.S. and Canada

You can also Google "alcohol free gas near me"

 

[toolmanmike]

Buy yourself a couple bottles of octane booster and carry it in the trunk. If you are forced to buy some weak gas along the way, pour some juice in and rock on.