What octane do you run in your K5?

[1-ton]

In the state of Nevada I run mid-grade. After doing some data logging with TunerPro on my OBDI/TBI engine I found that with regular octane fuel, and stock 0-degree timing my knock counts where a just little on the high side. With mid-grade fuel my knock counts where right on the money.

 

[wazzabie]

I'm still not clear. For the 78 350 to be in spec with the emissions decal should I be running today's 91 octane?

 

[Bent77]

I'm still not clear. For the 78 350 to be in spec with the emissions decal should I be running today's 91 octane?

If the engine is factory, you should be able to run 87. It depends on how your timing is set, so listen for pinging

Some run better on different octane

 

[eodcoduto]

Daily driver, stock ‘91 V2500 suburban and it gets 87.

 

[campfire]

I'm going with about 40.....


Cetane that is! In the red flavor, you know cuz it's farm use! Also some filtered waste oil depending on if I have any.

Came here for this answer. Wasn't disappointed!

 

[campfire]

I'm still not clear. For the 78 350 to be in spec with the emissions decal should I be running today's 91 octane?

No. Octane has been commonly measured using 2 different scales (RON and MON). In the US, the numbers on today's pumps are typically an average of the two methods ((R+M)/2). Older specs were written in RON, which measures higher than (R+M)/2 does (link1 link2).

91 RON = 87 (R+M)/2

So today's 87 octane is exactly what GM called for (aside from the Ethanol, which is a whole 'nuther discussion ). American gas stations just are using a different scale than back when that sticker was printed.

 

[ramack]

85

 

[4X4ForDad]

Ah, the good old Chevron White Pump! Yep 101-104 LEADED Premium. Sorry to see that go. VP is what I use now...Mega $$$. My diesel (cucv) Runs ok on B20 bio-diesel IF that is my only choice. Here in CA I'm seeing more "blend" diesel at stations...sad.

 

[ktmoutfront]

I put in 5 gallons of acetone in the Jimmy once in Baja Sur. It did not like it, but it got us to a Petrol station. Took two 1/2 tanks to really clean it out.

 

[Babaganoosh]

I put in 5 gallons of acetone in the Jimmy once in Baja Sur. It did not like it, but it got us to a Petrol station. Took two 1/2 tanks to really clean it out.

Put a big bottle of rubbing alcohol and 2 gallons of gas in my truck back in the day to pass emissions. The tail pipe was burning the guys eyes.