Non-ethanol vs octane

[76Caddy]

A Circle K convenience store just opened directly across the street from where I buy fuel and they have Non-ethanol.  I have been buying premium fuel for years to get the 93 octane.  Yesterday I got the Brougham out and it needed fuel, so I thought I would go and put non-ethanol in it, however the non-ethanol is 89 octane.  Question: which is better?  I know the non-ethanol is better for the fuel system but my cars run better on the higher octane.

Tim

[TJ Hopland]

In theory the 76's should be fine on 89.    What are the typical ratings in your area?   67 was a high compression motor so that may ping on 89.   What do you mean by they run better?  Hot starts?  Cold starts?  Pinging?  Hesitation?

[jdemerson]

Tim,

The compression ratio on the 1976 500-inch Brougham was 8.25 to 1. On the Seville it was 8.0 to 1. There should be no problem running 89 octane ethanol-free gasoline in those models. I'm skeptical that either would run better on higher octane. Have you experienced any pinging under load when using 89 octane?  You shouldn't...

My vote is a strong one for ethanol-free gas, unless one really needs higher octane (as with a 1968-1970 472 or 500).

John Emerson
1952 Cadillac Sedan 6219X

[35-709]

Agree, 89 ethanol free worked fine in my '73, in my mid '70s - 9.5-1 - 350 Chevy, and currently in my 1968 Bonneville, my 472 powered '35 Cadillac, and '67 460 Ford powered Speedster.

[76Caddy]

Thanks for the advice.  The Brougham did ping a little when I used lower octane but that was several years ago before I switched to the 93 octane.  I am going to use the the non-ethanol in both the '76's now that I can buy it and see how they do.

Tim

[impalamansgarage]

My 71 CDV has 8.5:1 compression and the brochure states that if you cannot find unleaded gasoline (ha ha ha...) then run leaded gasoline with at least 91 octane. It does not specifically say however what octane "unleaded" gas should be used. I ran 87 in it once and the engine did not like it. It pinged.

Anyway, I plan to stop using the E10 gasoline and just run pure gas from now on. My carb is a mess and I am going
through the whole fuel system right now.

So here's the issue. The closest 93 octane pure gas around here it about 45 miles away.

Can I put 87 octane pure gas in it and then just pour a bottle of octane booster into the tank?

[35-709]

I run 89 non-ethanol in my '71 472 without issue.  Are your choices only 87 non-eth. or 93?  If 89 or 90 is available and closer that should do well.  I am running 10 degrees BTDC for timing (factory is 8 for '71s). Being able to use non-ethanol is important enough to me that if I had to run 87 non-eth., I would set the timing back to 8 degrees, or even 6, to eliminate the pinging.  The last little bit of performance would not be as important to me as being able to run non-eth., my car is a cruiser and that 472 has plenty of power.

[TJ Hopland]

I would just run the E10 premium as long as you are able to drive it regularly and after you get things sorted out.   IF its going to sit for month(s) then I would make the 45 mile trek to get the good stuff.    That's how I did it for the almost 20 years and what I have done for a few tanks this summer.   Last week it was $0.90 more per gallon for the non ethanol stuff.  I knew it was going to be gone in about 4 days so I saved myself the $25.           

[GregoryAlan]

I use non-oxy gas in my old engines as well as all my lawn equipment!
Ethanol works fine until it causes a problem, if it causes a problem. My carb guy rebuild my Dodge carb and told me DO NOT RUN ETHANOL. The rubber will not survive. Take that advice as you will, it might work just fine for years and it might not...

If all you have for tools is your ear than the true test of gas that will/will not work in your engine is does it ping?

If you experience pre-ignition you might need a octane booster. [I guess you could back off your timing]
Over the counter boost doesn't really work well for my needs. I use a lead additive that works better for my needs.
Be aware lead will foul your cat and sensors if equipped to run unleaded gas...

http://www.overkillgarage.com/octane-supreme.html

[David Greenburg]

I would avoid the ethanol.  If the car seems unhappy on the lower octane, you can always add an octane booster.

[TJ Hopland]

Octane booster was the last question posed.  I have never heard good thing about most of them so I have never used them.  Sounds like some of you have?   Maybe let him know which brand and what mix ratio to use?

[EAM 17806]

Thanks for the advice.  The Brougham did ping a little when I used lower octane but that was several years ago before I switched to the 93 octane.  I am going to use the the non-ethanol in both the '76's now that I can buy it and see how they do.

Tim

I have been using 87 octane top tier gasoline in my 76 deville since 1977 and it couldn't run better.  I presume the owners manual suggests 87 octane after evaluating the old wording for what gas to use.  Just make sure the timing is where it belongs and you should be to be ok. This engine is a 500 cu (8.2 ltr) as were all 75-76 devilles, and I guess the Eldorados were too.  EAM

[TJ Hopland]

The 71-73 engines I have been into had a lot more carbon build up than 74-76's did.  I'm not sure if that had anything due to the design of the heads and huge piston dishes compared to the later ones or if the ones I saw just happened to be the ones that were only driven to church on Sundays.   

Carbon build up will cause pinging because it easily gets heated and stays hot so when the incoming air fuel mix comes in contact with it it can ignite it and often does ignite it.  The lower the octane the easier it is to ignite.  Higher octane won't ignite as easily so sometimes that is enough to keep the carbon from igniting the incoming fuel mix. 

The resistance to ignition is also why higher compression needs higher octane.  Compression makes heat.  More compression makes more heat and in a 10:1 motor that amount of heat is close enough to where lower octane fuel will ignite that it sometimes does so they tell you to run higher to give you some margin.  Some diesel engines are only in the 15:1 range and only use compression for ignition but diesel fuel needs a lot of heat to ignite. 

[David Greenburg]

I don’t know whether an octane booster would be beneficial for the lower compression ‘71 and newer engines, but I have definitely found them beneficial in my older (‘59-‘61) engines. 91 octane is the highest available to me, and until recently I lived up a pretty steep hill.  Without the booster, my old cars would knock going up that hill; with it, they would not.  When my ‘61 arrived from Dan, with a partial tank of presumably higher-octane, ethanol free Canadian gas, it managed the hill fine.  But as soon as I had to fill it with the local 91 octane corn juice, it would knock.  As for specific recommendations, all are not created equal.  The cheap stuff sold in gas stations etc. didn’t help. The better stuff, usually labeled for off-road use, works better; brands like 108 Turbo Boost, 104, and Lucas.

[fishnjim]

If you're not storing it for long periods(months) between trips, ethanol should be OK, if all the fuel system is converted for it.
Low compression does not require high octane.   I think they used to stencil "use premium gas" or something on the gauges back then.   

[76Caddy]

I was going to wait until I had checked mileage again before posting but I am switching back to premium 93 in both '76's as well as the John Deere lawn tractor.  I'm one of those ocd people who writes down every time I get fuel the date, mileage, number of gallons, price etc...  After 2 full tanks of non-ethanol in the Seville, it went from 15 mpg to 11 mpg.  After 1 tank in in the Brougham it went from 12 mpg to 10 mpg.  I could cut my yard twice on a tank before switching to non-ethanol but now I'm about half-way thru through the 2nd cutting when I have to fill up.
And FYI...everything is tuned up and running great.  I'm just wondering if maybe its the brand of non-ethanol Circle K is selling, all I know is my stuff don't like it and when I need fuel the next time, I going back where I had been getting fuel.

Tim

[TJ Hopland]

Most regions tend to end up all using the same base 'gas' from the same refinery.  Its the additives to get the desired octane, oxygenates, and other secret blends of herbs and spices that differs from brand to brand.  Just like any other product some brands use higher quality 'fillers' than others.    Sometimes some brands will truck their own stuff in and if you happen to live between 2 major refineries you could end up with product from either.

I don't remember what the base gas is.   Is a high grade and they 'water it down' to get regular?    Or is it all regular and they boost it up to make it better?   

[Dan LeBlanc]

I have been using 87 octane top tier gasoline in my 76 deville since 1977 and it couldn't run better.  I presume the owners manual suggests 87 octane after evaluating the old wording for what gas to use.  Just make sure the timing is where it belongs and you should be to be ok. This engine is a 500 cu (8.2 ltr) as were all 75-76 devilles, and I guess the Eldorados were too.  EAM

How can you have run Top Tier gasoline since 1977 when the Top Tier designation was only introduced in 2004?

[Dan LeBlanc]

I don’t know whether an octane booster would be beneficial for the lower compression ‘71 and newer engines, but I have definitely found them beneficial in my older (‘59-‘61) engines. 91 octane is the highest available to me, and until recently I lived up a pretty steep hill.  Without the booster, my old cars would knock going up that hill; with it, they would not.  When my ‘61 arrived from Dan, with a partial tank of presumably higher-octane, ethanol free Canadian gas, it managed the hill fine.  But as soon as I had to fill it with the local 91 octane corn juice, it would knock.  As for specific recommendations, all are not created equal.  The cheap stuff sold in gas stations etc. didn’t help. The better stuff, usually labeled for off-road use, works better; brands like 108 Turbo Boost, 104, and Lucas.

Yes, that was Atlantic Canadian 91 octane. 91 octane fuel around here is all ethanol free by legislation.

[Dan LeBlanc]

The way octane boosters are labeled are a bit misleading. When a bottle says it will boost octane by up to 4 points, it won't take 87 and boost it up to 91, it will boost it to 87.4.

There is a bevvy of discussions about this on Bob is the Oil Guy forums.