PREMIUM GAS ? OR REGULAR ?

[GarageGuy]

I assumed higher octane was better. Been using non ethanol premium. Anybody ? '70 1600 Fair Lady

[jrusso07]

i run non-ethanol but it's only 90 octane. I have run 93 and 95 premium with some Marvel Mystery Oil mixed in to prevent damage to metal and rubber parts. I do notice a difference but it's not enough to make me spend money on octane booster

[Gregs672000]

Depends on compression ratio and somewhat on how much ignition advance you're running, air temps and altitude. Octane refers to the ability of the fuel to resist exploding before its supposed to and in an erratic manner due to heat and pressure. An uncontrolled burn causes problems for the engine that sounds like rattle, or worse a loud knock. If the car runs fine on 87 run that. It's my understanding that 87 octane fuel actually has more explosive energy than 92. However, the engine will produce less power if the burn is erratic and can damage itself if severe.

My engine is at least 11 to 1 compression. I have it tuned to run on 92 pump, but it does feel much better (smoother, a bit more willing at low rpms under a high load) with an ounce of Boostaine which turns 92 into 96 in 11 gallons... just experienced this on a drive the other day. Cooler temps will reduce octane requirements, and you may have experienced a smoother running, more powerful engine at night or in cooler weather (I do). If I'm going to be seeing air temps higher than 80 degrees I will add the Boostaine for sure, especially if I'm gonna drive/pass at high speed.

Again, if the engine doesn't need it there's no sense in using higher octane fuel... it just costs more. BTW, I've never experienced any issues with ethanol fuel in my engines, but that's just me...
Hope this helps.

[david premo]

So in order to produce a fuel that will not have issues with pre-ignition octane values are increased to slow down the burning and reduce pre-ignition. Today they have gone to ethanol blended fuels that have extremely bad consequences for older carbureted engines as it will eat the float bowls and other fuel related components. So as the saying goes a picture is worth a thousand words, so I’m attaching a few photos of what it does to the carburetors from sitting in the float bowls. Fuel in a tank is stable for about a month, that said the number one thing that causes fuel to turn in the tank is oxygen. So I highly recommend that when you head home after driving for the day or several days, fill the tank up before you park your car and it will significantly slow down the process as there is minimal oxygen in your tank. Additionally one of the big problems with ethanol in gasoline is it absorbs water naturally and turns it into a corrosive product which eats holes in both aluminum and steel components. In a pure fuel, ethanol free as the fuel ages it turns but without any of the corrosive effects. If you go to Home Depot or Lowe’s they sell pure fuel for carbureted engines like generators, mowers and chainsaws as many of these products have far worse effects from these fuels with ethanol in them.
Dave

[Gregs672000]

Good pics of ugly stuff, clearly causing problems so no dispute here... I just don't know why I've never experienced or observed any problems in my own vehicle, be it in the tank, lines (all original) or carb internals, and I've been into them many times and in multiple set ups (80s era Mikuni, later SK Racing carbs, newer OER version, pre-2000s Dellorto, and now Jenvey throttle bodies). I've stored my car "poorly" at times over the years for months at a time, but it's remained fine. Guess I'm just lucky, or my car loves me! I do recall having to replace one check ball plate on the Mikuni when I first got them due to corrosion but they had been on a shelf for several years... that's it! These days I do make a habit of adding fuel stabilizer at the end of the driving season and topping off the tank, so maybe that's kept me trouble free... fires right up every year.

[Daryl Smith]

Irrelephant

[Daryl Smith]

Irrelephant

[redroadster]

Yeah 98 octane is recommended
Thats what it ran on in the 60s with leaded

[ARowe84]

I run 91 octane in California for years on my stock 1600. No issues. -Andy

[redroadster]

I wish they stop the ethanol additive , for the Corn sweat problem , 1 stalk of corn can sweat out 53 gal. of water ,with the close cover method they use now ,I believe it's why we are so humid now

[Nded]

Recreational boating is big around here (Largo FL), so lots of options. Half the stations have Ethonol Free 89 or 90. 1 mile from my office is a specialty fuel supplier called McMullen Booth. They have E-Free 93 at the pump, and an assortment of higher octanes in 5 gallon cans. Put in 5 gallons of E-Free 102, then top it off with E-Free 93, and you've essentially got 98 Octane. Does running 98 Octane make a difference in a stock 1600?

AND they have leaded gas for sale too (mainly for the racing community). I've never tried the leaded fuel in any of my 1960's vehicles ('65 Morgan +4, '66 Fairlady 1600). Should I give one a tankful?

[Gregs672000]

Only if the engine was re-tuned to take any advantage of a higher octane fuel beyond what it was designed for... octane need is based mostly on compression ratio and ignition timing. Higher octane does not equate to a more "powerful" fuel... it has to do with the fuels ability to resist exploding before desired.

[vorpal]

As Greg has said, if the car is not running higher compression or forced induction, the higher octane does not do anything. All it does is decrease the combustion window of the fuel.

[vorpal]

As Greg has said, if the car is not running higher compression or forced induction, the higher octane does not do anything. All it does is decrease the combustion temperature window of the fuel.

[rwmann]

Timing advance …