I am an new member to this forum. I have a '66 Coupe that ran out of gas after the sending unit failed. I got a gallon of gas from road side assistance that wouldn't take me too far soI was only able to put 91 octane in the tank so I shouldn't have filled it up I guess. Anyhow it's knocking now and I was wondering if there is a good additive that I can put into this tank only. I usually use Ultra 94 from Sunoco and it runs fine.

The car has a high performance 4-barrell 8 cylinder in it now.

Any thoughts?

Thanks!

 

If you only put a gallon of the 91 in than I would fill it with the full octane stuff you normally run. If that doesn't do it any octane boost addtive should work, just make sure you add it to a full tank of gas. You must have a high compression motor or lots of advance for it to be nocking with 91??? BTW welcome to the forum

 

Thanks for the advice. One more thing for today. I only drive this once a week or so and I got in last night and the battery was dead. The glove compartment was left open (light inside) so maybe that's what drained the battery over a few days. Anyhow, it boosted fine and I drove it for 20 minutes or so. When I put it in my garage I was able to turned it on and off a few times no problem but it was dead again this morning. Any ideas?

 

running a battery dead will literly kill it. Either you have a drain some where or you need a new battery. I would put a one amp trickle charger on the battery, should take a couple of days to charge up. Then see if it holds a charge. if not than have the battery tested.