Octane revelation

[camaroincal]

Well, I've seen many times discussed what octane to use in the 3.8 I always thought 87 was fine but as I was flipping through my Chilton manual it says to use premium gas if the compression is over 9.0/1 our cars compression is 9.4/1 Soooo...no more cheap stuff for me I guess lol. Anybody have any incite on the affects of using the cheap stuff as compared to premium in the 3.8? I have noticed recently in my car when trying to drive smoothly at low rpm's i.e. city driving, the car doesn't drive smoothly until I get over 2500 rpms. Could this be because of the crappy gas? I just changed the plugs and fuel filter and I have the K&N filter so my car is well tuned. Thanks

[SixBanger]

I notice a difference when I run premium gas in my car. It's nothing huge, but I can feel it. I get smoother acceleration. People say its bull**** to put high octane in a V6, but I'm skeptical. I believe it really does do some good for our cars.

[camaroincal]

Yeah I'm pretty sure that what octane you use in your car is determined by the compression and not the number of cylinders. As I understand it if you put the cheap stuff in high performance engines you get pre-detenation robbing you of horse power.

[HAZ-Matt]

The octane rating you use depends on your compression, ignition timing, and cylinder temp.

[Devilboy28]

I have been using 89 octane for a loooong time and switched back to 87 after many months. I swear it feels like my car runs ALOT better on the cheap stuff. Maybe it's just me. I'll switch to the 92/93 octane next tank and see if there is a difference.

[Jared Miller]

<blockquote>quote:</font><hr>Originally posted by SixBanger:
I notice a difference when I run premium gas in my car. It's nothing huge, but I can feel it. I get smoother acceleration.<hr></blockquote>

Yeah, same here... [img]tongue.gif[/img]

[mjparme]

I have been experimenting with different octane gas (87 and 91) for city and highway driving. In the city 87 octane gives me better gas mileage in the city but worse on the highway.

In the city I get 19 mpg on 87 octane but only 26 on the interstate. On 91 I get 15 mpg in the city and 30 mpg on the interstate. Not the results I was expecting but I have quantified it.

[camaroincal]

That's very intersting. I've never heard of the gas mileage varying so much just through using different octanes. I'll also have to experiment. :D

[Darknight]

Octane makes a huge difference in my car, and it's an '88 Old's Delta 88 with Series I 3800 with 318,000 miles on it. Besides giving more power and mileage, it runs smoother.

DK

[myrelease]

I've only had my bird a few months, and I figured that since it's mostly a sunday driver, I'd run 93 in it, get a bit more accelleration out of it. I find that the engine runs rougher on 93 than it does on 87. Thought I was crazy, guess Im not the only one!

[chas]

base timing (besides compression) determines the proper octane. higher octane fuels burn slower. if you engine is setup for 87octane, you should run 87 octane.

there are some exceptions. higher mileage (like 318k) vehicles might have carbon buildup (increases compression) and hot spots (can cause premature ignition) in the cylinders. you might need the higher octane to prevent knocking/rough idle.

i experience mileage variation between different vendors 87 octanes.

[RancidCamaro]

The owner's manual says use 87. The owner's manual was made by the people that made the car, I would think that they know best. I suppose different mods on your car could adjust your compression and timing, however, so that's the only time you should really ever have to switch to a higher octane. Otherwise, 87 is all that's really necessary.

[CamaroKing]

If you use higher octane than the motor was designed for, you may not be burning all of the fuel off, as the engine can't use it that fast. This would actually hamper performance. I know the 4 cylinder motors actually get unburned fuel build-up over time if an unnecessary grade of octane is used. I'd stick with what the car was designed for, and save some cash.

[Darknight]

High octane is one way to get your car to 318k, along with Pennzoil ;) Seriously, the paraffin in Pennzoil keeps a nice coating on all those parts, especialy the bearings and cylinder walls, and the slow burning high octane fuel protects the bearings and wrist pins from the shock of sudden releases of power that lower octane gasses produce.

Car companies recommend 87 for a few reasons. One, so they can list a lower estimated annual fuel cost. Two, because they automatically assume the driver would rather use 87 than the more expensive. Three, they have absolutely no reason to want your vehicle to last longer than the warranty. They are in the business to sell new cars when the old ones wear out.

DK

[camaroincal]

Darknight you hit the nail on the head man. I'm going to side with the Chilton's manual guys on this one. They said if you have a 9.0/1 compression you should use premium fuel. And our cars (3.8) are 9.4/1