87 octain or 91
 

i got a 77 dodge aspenR/T superpack,,318 4bbl,,have an argument with a friend on which fuel to put in which should i?????????im thinking 91 and go for the octain but he thinks since its unleaded fuel 87 is fine,just curiouse the pros and cons of both

Pinging or continues to run after you turn the motor off. If it does neither I would run the cheaper lower octane gas.

I don't know for sure, but I'll share my experience, fwiw. I've been told that I should use 87 in my '68 Polara 318 2bbl, but when I do, I get some pinging, but no run-on when shutting down the engine. With 91, I don't, so I use it. In addition, at least where I live in Canada, ethanol is added to gas. I understand that ethanol isn't good for the gaskets and seals in old engines. A few distributors offer 91 (or higher) without added ethanol. I use that. One is Shell "V-Power". If I am mistaken about any of the foregoing, please advise.

well i got a full tank of high test in the tank and is parked for the winter now .so i guess ill see what happens come spring ,,and yes i put stabil in ,ive only had her for 3 months and have been taking my time making her nice so its not even legal for the road yet ,,(no plates) but i did drive it to a near by lube shop and did a flush and put new oil in for the winter and did the tran while i was there to,,all clean all new filters as well k,n

300$ later

If it doesn't ping, run the low octane.

If it pings, try mid grade. If it still pings, run premium.

I run pump gas premium from 76 (Circle K) or Chevron and have no issues at all.

If you run too high of a fuel, you'll lose power, gas mileage, ect.

Would you happen to know anything about ethanol in gas as I mentioned above -- good, bad, otherwise?

Ethanol isn't that great for these cars... they want lead (which obviously isn't around anymore).

You may need to do some fine tuning on the carb for the higher Ethanol content, or find somewhere that sells GOOD gas.

Thanks for your view supporting that ethanol isn't good for old cars. That's why, as I mentioned above, I'm using high octane gas without ethanol. As you say, there may be a compromise on power and fuel economy and higher cost, but it got rid of the slight pinging I was getting with 87, and no ethanol to potentially damage gaskets and seals. If there was a mid-octane available without ethanol, I would've tried it, but it isn't.

77 is a no lead low compression motor, if it is stock.. Regular is just fine. I had a 77 Volare 318, it got what ever was the cheapest... Ethanol may require more octane depending- I would try a mixture 10 gal reg and 5 gal of Hi test to dilute the 10% ethanol used in today's fuels. There is a marine grade of stabil to deal with the ethanol..
I think the 10% mix is pure BS. They mix it and we get 10-15 % less gas mileage !! Where is the savings in that, and all the political BS subsidies to the corn industries

I always try to run the highest octane i can find. There's still one or two gas stations around here that sell 92 or 93

I'm on the coast in Florida and there are a few marina that sell no ethanol gas, but it's over $5.00 a gallon.

For what it's worth, I asked my mechanic about the lead/no lead and ethanol issues and he said that the older engines like mine ('69 - 318) are broken in well enough and probably have enough buildup on the valves that it isn't an issue. He only sees a problem when he's rebuilding an engine and puts in all new valves.
Michael

Perhaps so, but like I mentioned above, I heard that ethanol isn't good for gaskets/seals. Did your mechanic also leave you with the impression that this isn't an issue? If I could get absolute confirmation, I'd try switching from ethanol-free 91 to 87 with ethanol to save a few $.

mine has a performance cam old school 318 Streetmaster intake with a 4bll carter carb and hooker headers

scotty -

Agree with the consensus. The higher octane gas is to combat detonation/pre-ignition. If you're not getting the usual symptoms, don't sweat it.

If you're unsure with a given engine that may be high compression. I'd start with the higher octane fuel and work down until you get pinging, then go back up. The difference isn't that much with today's prices.

Humm, we have a few guys sell race fuel around here, but haven't seen no-Et-OH gas.

Archer

Shell ("V-Power") does, at least in my region of Canada, or so they claim and it's posted right at the pump. I think "PetroCanada" does too. They even offer a 94 octane.

68 polara,
I have no definitive proof for you but I can tell you this. I have always used the cheapest gas I can find in my old stock low compression motors, so no need for high test. Never a problem with the ethonal here. What motor do you have, 318? I am running three of those with no trouble. I might suggest your timing could be backed off a bit to correct that pinging. This is how I time my motors. Turn up the advance untill it pings under hard excelertion, then back it down. High mileage motors do not seem to like factory settings, as they have worn a bit and need to be tuned to need and not spec. Those spec.s make a good starting point. Don't forget that older motors can get carboned up and can cause hot spots that also cause ping. What kind of mileage is on your motor?
There is no problem with using the higher grade, just seems to me to be throwing money away. It is, after all ,your money and if it makes you feel better go for it.

As far as ethenal, I have read that it will eat away some rubber parts, ie. seals, pump diaphrams, fuel lines. Keep an eye out for leaks. When you need to replace these parts get the newer stuff made for this gas and no problem. These things need replacing now and then any way.

Thanks very much for your advice. My car is now in storage for the winter, a fair distance away from me, but I will save your reply and address it in the spring. It is a 318 2bbl with 76K miles on it. Cheers!

91km on it but motor was re built about 5k ago but thats befor i bought it so whats really been done under there is hard to say for sure unless i rip it apart ,and im not going to do that just cause im curious ,,,,i think from what im reading ill jut run reg fuel,,i just want the best for the car that i can get ,including all fluids ,,i dont want it to die

my dad has a 70 something 340 in his 77 roadrunner... he runs 87 in it all the time. Its got a purple shaft, edelbrock intake and holley projection (tbi) no pinging or detonation. so run 87. im sure you'll be fine.