What fuel octane do you use?

[1 Wild R/T]

First I agree with Chryco Psycho if you don't have hardened seats & you actually use your car for more than a show pony you need lead....

Second I'm my Challenger vert between milled closed chamber 915 (iron) heads & my piston/cam selection I have a static C/R of 9.7 & a dynamic compression ratio of 7.36:1 
I run 91 & on hot days when planning to climb a long grade like the Grapevine or La Questa I might dump in some octane booster just for peace of mind....

[bandt]

In Ontario we have 87, 89, 91, and 94 at some stations. Ethanol is always a concern. I have a 340 with iron heads. I use at least 91. Does anyone really notice any performance change? Higher octane just reduces detonation. My car I guess does run better on higher octane fuel I wouldn't say it makes any more power. No matter what fuel you use the specs of the engine don't change only the flash point does. 

[1 Wild R/T]

In Ontario we have 87, 89, 91, and 94 at some stations. Ethanol is always a concern. I have a 430 with iron heads. I use at least 91. Does anyone really notice any performance change? Higher octane just reduces detonation. My car I guess does run better on higher octane fuel I wouldn't say it makes any more power. No matter what fuel you use the specs of the engine don't change only the flash point does. 

In it's getting into detonation/ping then your risking damaging your engine, hopefully your brain tells you to get out of the gas... Hence you are leaving performance on the table....

Oh, BTW if you aren't getting off the gas that noise your hear is a explosion trying to shove the piston back down the hole before it reaches the top.. So yeah I think it hurts performance....


Oh, since that was your first post, I guess I should welcome you to the forum.....   

[Shane Kelley]

Both my 340's are 11.1  I run 93 most of the time. The Road Runner with the automatic transmission will ping with anything less. Never ran anything less in the Cuda. In Ohio they sell 100 octane at Sunoco right there at the pump. I usually take a bunch of cans when I travel there and bring it back. That's what I use for winter storage in the cars. I doesn't sour like most pump fuels. Doesn't stink the garage up when you fire the cars up to move them around in the buildings either. 6.99 a gallon.

These motors can detonate without you hearing it. It's called "silent detonation". You don't hear it but it's chewing on your motor. Either eating on your pistons or beating up your bearings or both. You can pull a plug and look at it with the naked eye and you won't see it. You need a little hand held microscope to see it. It will look like little specks of solder on your plug. That is detonation.

Here's the one I use from Amazon. They are cheap and will allow you to really read your plugs.

[bandt]

In Ontario we have 87, 89, 91, and 94 at some stations. Ethanol is always a concern. I have a 430 with iron heads. I use at least 91. Does anyone really notice any performance change? Higher octane just reduces detonation. My car I guess does run better on higher octane fuel I wouldn't say it makes any more power. No matter what fuel you use the specs of the engine don't change only the flash point does. 

In it's getting into detonation/ping then your risking damaging your engine, hopefully your brain tells you to get out of the gas... Hence you are leaving performance on the table....

Oh, BTW if you aren't getting off the gas that noise your hear is a explosion trying to shove the piston back down the hole before it reaches the top.. So yeah I think it hurts performance....


Oh, since that was your first post, I guess I should welcome you to the forum.....   

Thanks.
Maybe my post was badly worded. I'm not having any pinging issues. I was more talking about guys putting in higher grade fuel because they think it makes more power. If two 340's are identicle in every way including timing with no detonation issues with any octane and you put 87 in one and 94 in the other the only difference would be the cost of the fuel. Some guys swear there engine makes more power on the higher octane.

[1 Wild R/T]

In Ontario we have 87, 89, 91, and 94 at some stations. Ethanol is always a concern. I have a 430 with iron heads. I use at least 91. Does anyone really notice any performance change? Higher octane just reduces detonation. My car I guess does run better on higher octane fuel I wouldn't say it makes any more power. No matter what fuel you use the specs of the engine don't change only the flash point does. 

In it's getting into detonation/ping then your risking damaging your engine, hopefully your brain tells you to get out of the gas... Hence you are leaving performance on the table....

Oh, BTW if you aren't getting off the gas that noise your hear is a explosion trying to shove the piston back down the hole before it reaches the top.. So yeah I think it hurts performance....


Oh, since that was your first post, I guess I should welcome you to the forum.....   

Thanks.
Maybe my post was badly worded. I'm not having any pinging issues. I was more talking about guys putting in higher grade fuel because they think it makes more power. If two 340's are identicle in every way including timing with no detonation issues with any octane and you put 87 in one and 94 in the other the only difference would be the cost of the fuel. Some guys swear there engine makes more power on the higher octane.

In that case   

[HP_Cuda]

Always the highest I can find.

That would be 91 unless I make a special trip over to grab 100 octane ethanol free gas. There is a station on the way to my office which carries all the Torco fuel lines.

[MOPAR MITCH]

Here in the midwest area (Chicago-area, Milwaukee-area, Indianapolis-area, Detroit area, St Louis area, etc) I run premium no-lead 92-93... just fine for typical "driving -- street, highway, etc).  But, if I'm doing some aggressive driving -- track activity... HPDE, HSAX,. AX, etc -- then I occasionally add some 104 Octane boost, or better yet, if there is ~95-100 un-leaded premium, the engine seems to really like that fuel.  Caution, I've found -- NOT to switch to some leaded gas, such as ~100-103-105-110... the car will NOT run on that fuel.. really crappy... hesitates, stalls, black smoke, etc.... probably requires re-jetting which I'm not doing for a single day at the track.

'70 Challenger T/A; 340-6-pack, stock grind hyd cam, Hooker 1-3/4" headers w/ 2.5" pipes and Flowmasters, Mopar Performance Chrome box ignition, 10.5:1 TRW pistons, mildly ported standard x-heads/match ported intake; beefed 727 ~2400 BM Holeshot, 3.23 rear 8-3/4 rear.   Car cruises the hwy at ~3400 rpm (~70 mph); engine revs to easy 6-6500 when on track, averaging ~4000-6000 rpms for lapping sessions).

Next engine may be a ~408-416!... within next 1-2 years.

[chargerdon]

Here in NC the gas comes in 87-89-93.  In my 66 Charger wth HP383, and a 224 duration cam, i run 89...   i had the static timing set at at factory 12 BTDC.   At that setting there was no pinging using regular (87 octane 10% ethanol) gas.  Then read an article that says that the unleaded 10% ethanol gas we buy today has a slower flame front than the old leaded gasoline so that we should run 2-4 degrees More than what the engine called for back in 1966.   So, upped the timing to 16 and the engine does run a whole lot better..especially off the line, BUT it would ping on 87 badly, lightly ping on 89, but with a cheap octane booster in each tankful runs good with no pinging.  So 89 it is with 16 BTDC.

On my 74 Challenger with built 360 (Mopar Purple 508 cam 248@50 overlap 9.75 static compression) to get decent (not great) idle had to advance static timing to between 20-22 BTDC anything less and the idle is really really rough.  At that setting it will idle at 800-1000 rpm while in gear (904 torqueflite) REQUIRES 93 Octane to not ping, and to start easy.   So 93 it is for it....   Ticks me off because 93 octane costs $.60 a gallon more than 87 at most stations, and it only gets 10-12 mpg unless i baby the hell of of it...and whats the fun in that?

[CudaMoparRay]

Both my 340's are 11.1  I run 93 most of the time. The Road Runner with the automatic transmission will ping with anything less. Never ran anything less in the Cuda. In Ohio they sell 100 octane at Sunoco right there at the pump. I usually take a bunch of cans when I travel there and bring it back. That's what I use for winter storage in the cars. I doesn't sour like most pump fuels. Doesn't stink the garage up when you fire the cars up to move them around in the buildings either. 6.99 a gallon.

These motors can detonate without you hearing it. It's called "silent detonation". You don't hear it but it's chewing on your motor. Either eating on your pistons or beating up your bearings or both. You can pull a plug and look at it with the naked eye and you won't see it. You need a little hand held microscope to see it. It will look like little specks of solder on your plug. That is detonation.

Here's the one I use from Amazon. They are cheap and will allow you to really read your plugs.

Great idea, I already have a professional microscope from my Microbiology days that I can use on low power to see the spark plugs with

[RUNCHARGER]

My understanding is higher octane fuel does not make more power by itself. What happens though is if your engine detonates you are damaging it, if you back off your timing so it doesn't detonate then you are losing power.

[Chryco Psycho]

Welcome @bandt   
Glad you made it here at last 
the best fuel to run is the lowest octane where it will not detonate , more octane is not helping if it is running right
Having said that if you use higher octane fuel & you can tune more performance out of the engine then it will help
As wild said poor fuel Will hurt perfromance

[Chryco Psycho]

The other factor that come into play are Use / powerband / cam design
I ran my 440 Duster for 9 seasons  , it had real 11:5 compression with milled closed chamber iron heads & a 312* ad duration cam  & ran fine on Sonoco Gold 94 octane to a point , if you dumped the clutch at 1200 rpm & opened the throttle it was like there was a bag of marbles in the engine  , It would ping like crazy but give it a chance , stay out of the throttle until it hit the powerband around 3400 rpm & it was happy , or dump the clutch @ 4000 & no problem it was not finished pulling @ 7200 rpm where I shifted it ! I did run it on AV gas too !!

[cudabob496]

I add Torco booster and then add Redline leaded substitute since I still have stock heads on the Hemi.

91 is the highest unless I go to the high Octane gas station.

I've read you really don't need the lead additive.

& you believe everything you read ? Without lead the exhaust valves will weld to the seat & tear away material every time they open , you either need stellite seats or some kind of additive , I have seen valves recessed over 1/4" deep into the head .

No, but when I read it more than once, and hear it from different racers, I tend to believe it.

[cudabob496]

The statement below is pretty much what I have seen over the last 20 years. If you are just a street car,
that rarely gets up to 6000 rpm, and doesn't stay there long, I think you are wasting your money, and poisoning
yourself with lead additives. Machinists I know that have torn down engines have not observed damage to soft valve seats,
in street cars, with unleaded gas. As another site I just visited said, the "potential for damage is overblown"

Again, using leaded products is quite dangerous to ones health, and the people around you!!

"While concern over valve seat recession in older vehicles has been raised as an argument
against the complete conversion to unleaded fuel, the actual incidence of valve seat recession in
countries around the world is small even in vehicles with "soft" valve seats.2
Only vehicles which travel consistently a very high loads and speeds appear to be at all vulnerable in actual use. And
even for these vehicles, additives other than lead have been shown to protect valve seats."