Which Octane/Which Engine?
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
87 octane. 89 if 87 isn't available.
The only reason to run a higher octane - well, the only TWO reasons to run - is that a) the company puts the better detergent package in the higher octane gas (and you can handle this by using an add in detergent every so often, like Seafoam or Techron), and b) your wallet is too heavy and you need to lighten it.
(That's for the Magnums; us with the older LAs can add a few degrees of advance to make the engine run a bit more potently, but it'll create preignition, so we'll run 89 octane to 93 octane to counter that.)
IF you're getting pinging on 87 on a 94-96, it's carboned up - time to check the plenum gasket and do some cleaning if possible.
RwP
The only reason to run a higher octane - well, the only TWO reasons to run - is that a) the company puts the better detergent package in the higher octane gas (and you can handle this by using an add in detergent every so often, like Seafoam or Techron), and b) your wallet is too heavy and you need to lighten it.
(That's for the Magnums; us with the older LAs can add a few degrees of advance to make the engine run a bit more potently, but it'll create preignition, so we'll run 89 octane to 93 octane to counter that.)
IF you're getting pinging on 87 on a 94-96, it's carboned up - time to check the plenum gasket and do some cleaning if possible.
RwP
Professional
Joined: Feb 2015
Posts: 119
Likes: 3
I use mostly use 87 octane (which is factory recommended) but I notice a slight ping when accelerating from a stop sign sometimes. If I opt for premium (91/92 octane), the slight ping is eliminated. This is a 1996 3.9L 4X4 five-speed with a 3.55 ratio ring and pinion and 290,000 miles on the odometer. I usually am too cheap to fill up with premium, but I guess I could try half/half (no mid-grade available where I am).
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
I'd also send a few of the larger bottles of Techron through the fuel system.
Possibly a steam clean - ala Seafoam's usual method, even if it's with something like Berryman's Chemtool B12 (which is what I used decades ago, and is still available!)
You can also go a temp range colder on the plugs and see if that helps any.
The slight ping is probably due to carbon buildup in the heads; not much, but enough to raise the compression JUST enough to ping at times.
RwP
Possibly a steam clean - ala Seafoam's usual method, even if it's with something like Berryman's Chemtool B12 (which is what I used decades ago, and is still available!)
You can also go a temp range colder on the plugs and see if that helps any.
The slight ping is probably due to carbon buildup in the heads; not much, but enough to raise the compression JUST enough to ping at times.
RwP
