Hi guys. Has anyone here at Moparts ever tried running 90 octane recreational gas in there 9.5 to 10.0 compression 440 motors? I was wondering if the engine would knock on that low of octane rating. My 440 375hp engine seems to run fine on 93 octane Super Shell, but that's 10% ethanol, and that's what I'm trying to get away from. Thanks.

Maybe you can find something here: https://www.pure-gas.org/index.jsp?stateprov=MI

Thank you, but I've seen that site before. I already know where the gas stations are in my area that carry Rec Gas. What I'm asking is: Has anyone here at Moparts tried running a 440cu 375hp engine with 9.5-to 10.0 compression on 90 octane ethanol free gas.

Well, I can tell you two things. 1) Rec fuel is all I run in my 2016 Challenger 392, & it works great. 2) I would not run ANY fuel with ethanol in it in old muscle.

Try it & see.

I actually run EF90 in my Hellcat on the street w/black key. Track days I mix with 93. I would really like to pick up a drum of Sunoco GTX to mix. Maybe next year.

Thank you for that info, but I don't have a modern day computerized Hellcat engine. I'm talking a old school motors with 10 to 1 compression in a 60's muscle car. I suppose I'll just have to go buy 5 gallons and try it. I just hate wasting $20 bucks if it won't run right and possibly harming my engine.

The ethanol free is 91 here and I have no trouble running it in my G2 11.5 to 1 aluminum head 426 Hemi.

Thank you for letting me know that. Our ethanol free Rec Gas here where I live at is only 90 octane, but I guess 1 octane point won't make much of a difference, I hope.

You're welcome. It'll help but it will still have have some problems with heat soak sometimes and carbs will go dry after sitting for more than 3 days without running and need to refill when cranking with mechanical pump. It you run an electric pump no problem. If it doesn't fire right up hot don't give it any more gas just hold the pedal down as if it's flooded and it'll start.

Is your 440 a real 10 to 1 engine ? has it been rebuilt with pistons that are way down the deck height, the only way to know if the rec gas will work is to try it.

I've race Mopars since 1964, I build my own motors and have torn down a bunch of early,1967 up to 1971, 440 magnum (HP) motors, none of them where any where close to having the piston deck heights and combustion chamber volume where they should be to make the advertised compression ratio, they all had true lower compression
On your deal I would try it to see if you can notice a difference or not
Please let us know what you find, that will help others on here
I have not heard the term "recreational gas" , maybe it is not sold here in central OR
I run my S/P bracket car on E85, the station that sells it also sells all kinds of race gas from their pumps
Non ethanol gas will make more power and go further down the road(better mileage) than the E10 or E15 will with the same amount of fuel

Hey OP, my RB is 10-1, I run 90 with no knock ever.
Track days I'll dump some 100 in.

Thank you, that is the info I was hoping to hear. I'm going to try some and see how it runs in my 440. I appreciate you guys input. Thanks.

i have a 520 ci wedge that has a true 10.2 comp. the rec gas in this area is 89 octane ,no prob.at all

Thanks bonefish, That's very helpful info.

Does the 520 wedge have aluminum heads?

Yes, I was wondering the same thing.

Roger dodger .... alum heads and a super efficient exhaust system

There is no lead free fuel in these parts.92 octane with 10% corn. At 6 lbs of boost I'm just under 13:1 with no issues.That is the limit before more octane is needed.