Tlo154

Any recommendations on which fuel and/or additive may be better for the older original engines like my Rocket 350 in my 76 Cutlass Supreme?

oldcutlass

I've been running the ethanol in my old car for years, there is no non ethanol here where I live. No Issues.

Fun71

Same here. My area has "oxygenated" fuel (10% ethanol) and my car has been running fine on it for the past 15 years.

jensenracing77

If it is stock, a 350 engine from a 76 Cutlass will run on most anything you find at the pump and be safe.

MDchanic

+1 to all.

Not much to add, other than that the ethanol fuel will run slightly leaner with stock jetting, so if you're really obsessive, you might get a small improvement from a stock engine by going slightly larger on jets / smaller on rods.

Or you may completely screw it up.

- Eric

Lady72nRob71

If there is a choice for 15% ethanol for a lower price, I would avoid it. 10% is bad enough but we do not have much choice.
Just keep an eye on your rubber fuel lines for hardening and leakage more often. Having a spare fuel pump on hand may be a good idea also if the car sits for long periods of time as the fuel will seep back to the tank and rubber diaphragm will dry out and eventually crack. I have experienced more failures like this with ethanol gas than without but not sure it is a 100% correlation...

1970cs

No issues so far, but I finally put some anti-ethanol additive in my tank last week as a safe guard.

Pat

popeye1978

When manufactured, did your '76 run leaded or unleaded?

Something to be careful about -- and for which you might have to do more research -- is that in the '60s gas was sold at a certain octane as measured by MON or RON while today it is sold as measured by AKI (= MON + RON / 2). I don't know when the changeover actually occurred for good, but worth looking into as your Cutlass may have been manufactured during that gray area

Also, be aware of where you buy your gas -- depending on your area, generic or supermarket gas stations will probably get their gas from the same distributor as the local big chains like Sunoco or Shell, but the chemicals they add (for their marketing purposes) will be different ... from discussions with co-workers, all of us think our cars run better with gas from a good chain than from the local supermarket chain (same octane).

All told, my '67 Mustang runs better with 93 from Sunoco than 87 Regular, turns-out (when I did my own research two years ago) that 87 today would've been "sub-regular" when the car was manufactured

RocketDevo

I read an article stating that Shell gasoline has more energy per unit that most all other brands, due to the fact they do not "water it down" as much as others companies. Most fuels have various additives, Ethanol being a large component, which is not as volatile as petroleum. As a previous member replied the Octane level of todays fuels is much lower than what you could buy in the day. I would not use to low an octane number, such as 87, these cars were not made for that low. In another article about detonation, they stated on a scale of 1-10 you basically do not hear detonation till a level of 7, so it can still be occurring without you audibly aware. Hope this helps.

Fun71

The OP is talking about a low compression, smog era 1976 350 engine (catalytic converter, EGR, etc.) that was designed to run on 87 octane unleaded fuel, not a 60s era high compression, high output engine.

oldcutlass

I agree, the op's should run on 87 with no issues. In 76 there was still regular leaded, unleaded, and if I remember right gasohol was introduced around that time. The op's was designed to run on unleaded.

Olds442redberet

My car requires high octane fuel to run properly. I have no issues with running 92 octane unleaded.
The mechanics put 87 octane in her after the rebuild and had a heck of a time getting her to run decently. I ran half a tank of 92 octane through it and we were able to finally set the timing, vacuum, and adjust the carb properly. I have not had any issues since.

jfb

I only have 1 thing to say for Chicago shell gas only and maybe it applies there also,shell gasoline goes flat quick and the octane rating is ok. bp gas is decent though. I use now 93 plus race gas additive for unleaded because lead is no longer really needed with newer heads. I use straight race gas at the track by the way I am over 11 to 1 on the street with a long cam.

RocketDevo

The OP wanted a recommendation on fuel, and I gave my opinion. I did not talk about Lead as I know the engines were changed for this. I mention about the energy per unit, of gas which I believe the OP was wondering about. I know his motor is not a high compression 60"s motor, but 87 octane in 1976 was at the bottom of what petroleum companies offered. 87 Octane now is not what 87 Octane was in 1976. I further mention about Detonation which is one of the main issues you have with todays fuels.

MDchanic

No, 87 octane now was called 91 octane in 1976.
The "RON+MON/2" or AKI octane rating number was required to be displayed in the US starting around 1980 or '81. Before that, the RON (Research Octane Number) was used on pumps, which is about 4-5 points higher than the AKI.

Detonation will occur in engines where the actual dynamic compression ratio (as determined both by the static compression ratio and the valve timing) is too high for the octane used. You will not get detonation with 87 octane fuel in any engine with a 7.5-8.0:1 actual static compression ratio, as found in all stock US cars in the late 1970s.

- Eric

RocketDevo

MDchanic if you read what the Op asked, he wanted a recommendation. I gave an opinion that's it. I mention about detonation it is only a component of what is being talked about. I am not sure if you are trying to say 87 now was 91 then? The bottom line, all things being equal, gas today is not the same as back then! What I am saying, If you set your car's timing, if it is completely stock to the specs GM stated. It will not run with todays gas as it did back in 1976.

MDchanic

The only reasonably accurate recommendation is that his car will run fine on low-octane unleaded gas, and needs nothing more, unless he wants to fine-tune his mixture, or needs a stabilizer for long-term storage.

Your opinion is fine, but as his low-compression engine will not detonate on 87 octane US gasoline, your repeated mentions of detonation are irrelevant and confusing.

What I said, and will repeat, is that the gasoline that is labeled 87 octane today in the US would have been labeled 91 octane in 1976.

It is true that US gasoline is not the same as it was then, for several reasons:

• You could buy leaded gasoline at regular gas stations in the US in 1976, as well as unleaded.
• By 1976, true high-octane leaded gasoline was getting hard to find. The best that was usually available was mid-grade.
  Unleaded was available in the equivalent of our current 87 octane only - there was no such thing as Unleaded Premium.
• US gas is now extensively mixed with alcohol compounds, which introduce additional oxygen molecules into the gas, at the expense of carbon molecules, which gives a given volume of modern gasoline less energy than it would have had in 1976, and renders the calibration of carburetors jetted for the older gasoline inaccurate, causing them to run slightly lean.

If you set the timing of a 1976 American car, such as the OP's, exactly to factory specs, it would be timed exactly as intended by the factory.
It would run slightly differently because the alcohol in the fuel would cause it to run leaner (unless you used non-alcohol gasoline), but its operation would be otherwise unaffected.

- Eric

popeye1978

Eric, I'm confused -- in 1976, if you bought "Regular Unleaded," what octane was it (we'll assume the octane is by RON as you previously stated AKI wasn't required until the early '80s) ?

Denys

MDchanic

"Regular Unleaded" until somewhere in the mid-eighties (if I recall correctly) was about 90-92 RON or 87-89 AKI.

"Unleaded" used to be synonymous with "Not Premium," and there were several years in the early eighties between when they stopped selling leaded in gas stations and when they started making real unleaded Premium, when you essentially couldn't buy Premium gasoline in the US.

- Eric

Koda

If you can find non-ethanol, I'd run it.

If you can't, I'd run Marine Grade Stabil (it's blue) which is the normal fuel stabilizer and and is a corrosion inhibitor and an agent to prevent fuel separation.

KDV

Mine's not a daily driver, so I'm running Sunoco 110.

The Ohio Valley is a dumping ground for sh**ty pump gas.

Ozzie

Around me non-ethanol fuel is still being sold by Pure Oil stations, some independents, and some marine stations. I prefer it, but the price difference is about +40 to +60 cents per gallon, and when I go away from home I have difficulty locating anything but "contains up to 10% ethanol".

Leadfoot

In my mind, the potential performance issues can be minimized by tuning. As Eric pointed out, the octane rating is really not an issue once you understand how to compare 1970's ratings with 2014 ratings. Performance alone shouldn't be much of a concern.

The bigger issue to me is that the ubiquitous ethanol and other modern fuel additives can wreak havoc with the rubber and other soft components used in our older cars' fuel systems. I've seen modern pump gas turn old fuel hoses to mush, so a good fuel conditioner can be cheap prevention. A systematic upgrade of rubber fuel system components is to me the most sensible approach.

I'm still on the fence about issues of modern unleaded fuels in engines with unhardened valve seats... but I think (assuming that it's a '76 engine) the OP's '76 should not have that issue anyway.