Corvair Forum

I have a '65 Corsa Turbo. The owners manual suggests using premium gas - of course that was back in 1965 when gas was leaded.

The Shell station I use has the usual Regular (85 octane), Plus (89 octane) and V-Power (93 octane) gas and all these selections contain 10% Ethanol (something which wasn't available in 1965).

However, they also have a Regular (85 octane) product available which does not have Ethanol alcohol in it.

So, for those who have an opinion, which modern day gas would be better for an old turbocharged corvair - the 93 octane + 10% Ethanol gas or the 85 octane alcohol-free gas ?

Alec

I wonder if the octane rating is post the ethanol mix-in? It's all junk these days. On old motorcycles (air cooled) there seems to be an advisement to use a bit of two stroke oil or similar (marvel mystery) in with the gas to lessen the damage that ethanol is known for. As far as octane the 1970s high octane is known to be similar to our modern mid/unleaded grade. In my corvair I have an ampco oiler that I keep full with marvel and I run the cheapest gas I can find but it's an 80hp and not turbo. Ethanol laced fuel is usually higher in octane because ethanol itself is harder to burn than gasoline. Running that non-ethanol 85 may be a bomb. That's a good fuel to start bonfires with though. (This all comes from my limited knowledge of gasoline.) Some of this information may not be correct.


Sent from my iPhone using Tapatalk

You still need premium fuel regardless of the Ethanol. Realize that in 1965, premium should have been 97 or 100 Octane. There were some Super Premiums that were 100+.

85 octane will not have the correct burn rate and will cause knocking.

Here is a good read by Hemmings:

https://blog.hemmings.com/index.php/201 ... ced-fuels/


Sent from my iPhone using Corvair Forum mobile app

SyntheticBlnkerFluid wrote:You still need premium fuel regardless of the Ethanol. Realize that in 1965, premium should have been 97 or 100 Octane. There were some Super Premiums that were 100+.

85 octane will not have the correct burn rate and will cause knocking.

Here is a good read by Hemmings:

https://blog.hemmings.com/index.php/201 ... ced-fuels/


Sent from my iPhone using Corvair Forum mobile app

Lol oops I had it backwards. Sorry.


Sent from my iPhone using Tapatalk

There are so many opinions on today's fuels.

First - today's octane ratings are NOT calculated the same as back in 1965. Go to https://en.wikipedia.org/wiki/Octane_rating
and read. So in the old days the 100 octane fuel would be about 93 today (U.S.A./Canada rating now - Europe is different).

Second - Ethanol has a higher octane rating, so it actually helps prevent detonation. Yes it's air/fuel ratio has to be denser, but remember most fuels have less than 15% ethanol so don't get overly concerned about running a richer mixture with today's fuels. Traditionally folks have run richer mixtures to keep cylinder/piston temperatures down - fine for racing but it can ruin a daily driver engine over the long haul.

Today's fuels boil/evaporate at a lower temperature due to the removal of "lead" additives and yes ethanol aggravates this, but the main problem is today's gasoline is refined to boost octane without "lead" and that is the major factor in today's more volatile gasoline. An electric fuel pump gets around most of the "hot start" or dry carburetor issues.

Finally - in spite of all the talk - most Corvairs run just fine on today's premium gasoline. Ask around. One problem is letting a car sit a long time between drives. Being old I know gasoline goes bad, always has even before ethanol, if you let a car sit for months without a fuel additive for storage.

BTW - Known Corvair turbo expert Steve Goodman advises using a good fuel pressure regulator and setting it to 2.5lbs at sea level (lower at higher altitudes).

Hello Alec, To Answer your question in a nutshell 85 -89 Octane should work well in your stock format Corvair engine, I deal with science of Gasoline every day and have seen big changes to the products in the last 30 years. Because the engine manufacturers have to continually improve their technology every year, they just can't meet all of the emission standards imposed on the them, so they have reached out to the fuel producers to help them.That is why they have been adding ethanol to their products, it's cheaper to manufacture than octane (Trimethylpentane) and actually has a higher rating. The down side to Ethanol is it has a short life span and is very hard on fuel pump diaphragms and the neoprene needle and seat in your carbs. The reason they removed lead from fuel is it is not compatible with the catalytic systems of modern vehicles, and it added to smog. Some mechanics and engine builders believed that lead added to upper cylinder lubrication (not true). It also was added as a octane stabilizer. To summarize use a good name brand fuel, I use 89 octane with Ethanol in all my old cars and I have six Corvairs and three VW bugs and a 49 Ford pickup (all stock). Here are some tips for you guys. Any modern day gasoline only has a shelf life of 30 days, then it starts to stale. Seasonal fuel stabilizers are crap. Try and run your fuel out at the end of the season before storage, and in the spring add fresh fuel. Over the counter fuel injection cleaners are a myth too. The same products are already in most modern day fuel, just in a lower concentration. Finally I have been adding Stihl two stroke engine oil to all my old car's fuel for years, and it works great as a upper cylinder lubrication. No plug fouling and it seems to extend the fuel system rubber parts from Ethanol damage. It also keeps the combustion chambers cleaner at low engine speeds. I add 3/4 of a pint of oil to a full tank in my Corvairs it seems to be a good ratio and it burns clean - no smoke or foul odor from the tail pipe. One side note to your octane selection if you have a turbocharged Corvair or you live in hot climates than you should always select the highest octane fuel you can buy.

Hope that helps Jim

acarlson wrote:which modern day gas would be better for an old turbocharged corvair - the 93 octane + 10% Ethanol gas or the 85 octane alcohol-free gas?

Define 'better'?

If driving cheaply is your goal, the answer is obvious. If you aim to drive on boost at all, you need as much octane as you can get to avoid detonation reliably. Then again that's warm weather advice, generally speaking when it gets as cold as it is right now (30's) you can drive as hard as you want and you have the opposite problem- the engine never warms up enough for detonation to be much of a problem.

The answer I like is best is put 87 in it and listen for pings. If it doesn't give you issues and you can't hear the rattle can, you're probably fine. But once the outside temps creep above about 65 come spring time, that all goes out the window.

You have to understand, this engine is pretty prone to detonation with it's bathtub combustion chambers and Neanderthal style ignition system. There are no safeguards in place to keep you from melting the thing into a pile of aluminum should heavy detonation occur, so you need to be on your tuning game. Know what AFR's are safe, and what timing advance gives the best performance. Without knowing those things, you're doomed to owning a 180 engine with a useless turbo system.

I wouldn't even try to go the cheap route. 91 or higher octane is all you should be putting in a turbo motor.

Yeah premium $.60+ more expensive, but I'd rather pay that than damaging the motor.

My dads '64 110 (which is also a high compression engine) is only happy with 93. Anything lower and it pings.


Sent from my iPhone using Corvair Forum mobile app

my dad use to fill his mostly with premium (with ethanol) and a gallon or 2 of aircraft grade fuel (think it's like 5-10 bucks a gallon?). granted that side ofnmy family are in the aircraft industry in some form or another and has connections with our local airport, so they could get the gas that isn't legal to use in aircraft due to age (strict regulations and all) however was still perfectly fine. an idea maybe?

personally i would suggest just get the premium. of course you could try the ethanol-free gas and add in octane booster maybe? and judge how the car performs in both situations.

the main thing to remember is ethanol will eat through the mechanical pump's diaphram pretty quick so if you still have one i'd recommend either swap to an electric pump, or keep an extra mechanical pump or 2 in your trunk as well as tools needed to do a quick replacement. i've personally experienced beoling stranded due to the diaphram being too far gone finally and causing a slight air leak in the fuel line.

just a few thoughts of my own on the matter, i'm by far still a novice. however, on my 1967 monza 110 (non-turbo) premium ethanol gas works just fine. sometimes i mix a bit of octane booster in but it hasn't been really necessary, the difference i notice is minimal.

Sent from my SM-G920V using Corvair Forum mobile app

OlCorvairguy,

Thank you for your insight on gasoline. As far as pinging is concerned, I wonder about those who are running a Megasquirt or something similar with knock sensors. Anyone out there want to comment?

I have Megajolt does that count? :p

No knock sensing, but crank trigger and mapped advance helps a whole lot in avoiding knock related problems.

Ethanol free 85 has me curious. I haven't seen that around here. I bet my 80hp would love that. I would still say higher octane for the turbo to be on the safe side. We also have to understand that the turbo on that vair is a very different system then a more modern car. A little vw turbo these days makes peak boost at very low rpm as do most cars. If a corvair were engineered today that turbo would be much smaller and would kick in way sooner.


Sent from my iPhone using Tapatalk

My Corsa has an electric fuel pump - not sure about rubber diaphrams in that.

lostboy wrote:Ethanol free 85 has me curious. I haven't seen that around here.

Yep - but it's not cheap. About the same price per gallon as Premium. I have friends who claim they get much better mileage with it vs gas laced with ethanol. Looks like I'm going to stick with the higher octane fuel for my turbo. This has been a great discussion though - THANKS everyone for your feedback !

Alec

acarlson wrote:My Corsa has an electric fuel pump - not sure about rubber diaphrams in that.

lostboy wrote:Ethanol free 85 has me curious. I haven't seen that around here.

Yep - but it's not cheap. About the same price per gallon as Premium. I have friends who claim they get much better mileage with it vs gas laced with ethanol. Looks like I'm going to stick with the higher octane fuel for my turbo. This has been a great discussion though - THANKS everyone for your feedback !

Alec

I believe it. You usually give up mpg on ethanol.


Sent from my iPhone using Tapatalk

E85, or Flex Fuel, should never be used in cars that are not specifically designed for it. It is typically only found in the MidWest and is usually 50 - 85% ethanol. Tests with a fleet of flex fuel Ford cars found E85 averaged about 6% less MPG, but was cheaper than gasoline. Bottom line, gasoline with ethanol added at 10% or less has a negligible impact on MPG, in spite of folks perceptions.

Ethanol is NOT CORROSIVE, but Denatured (unfit to drink) ethanol can be mildly corrosive (varies with refiner) to meet the Denatured requirements.

Most ethanol blends available in the greater U.S.A do not exceed 10% ethanol. Most if not all electric fuel pumps are rated for ethanol blended fuels (15% or less).

One issue is that you have to make sure the rubber fuel lines are rated for ethanol blended fuels (some of the cheapo FLAPS stuff is NOT). I used Gates Barricade flexible fuel lines that work great for years.

You guys interested in the ethanol story should watch "Pump" on Netflix, although I don't know how accurate it is.


Sent from my iPhone using Tapatalk