Gas octane ratings.... mix ??

[Moxie26]

In past readings, I've seen octane ratings being reported around 70 in the Model T days.... With today's today's gas at 87 octane, that may be reflected as premium in modern terms for the Model T.. just questioning with modern cars. ....If regular is mixed with premium, does it really raise the octane rating of the gas in the tank?.. and by how much compared with the volume of premium added to the mix?.. answer from The Forum will help a past group chat. Thanks .

[Daisy Mae]

Mixing different grades will raise (or lower) the octane rating depending on your reason/target. The end result will simply be the average of each octane level relative to the quantity of each mixed. Generically a 50/50 mix reg/prem will equal a mid-grade.
The question is, why go to the bother??

[DanTreace]

70 rating may be a bit high for typical gasoline for autos in the 1920s. About 60 octane would be more in line.

Notes from a 1980 paper on fuels for autos and aircraft in the early years. The number mentioned are from 1914.

Although octane number ratings were still more than a decade away, estimated octane numbers would be 45-55 for American fuel and around 70-75 for Rumanian, Dutch East Indian and California gasolines. In Europe, batches of aviation fuel were selected for engine performance on a trial-and-error basis and the only known method of remedying unsatisfactory quality was to add coal tar benzole up to the limit (ca 20%) dictated by the need to avoid solidification in cold weather.7
Thus, until well into the First World War, motor spirit for both ground vehicles and aircraft was merely a low gravity, straight run distillate with aircraft stocks being selected from crude sources known to provide superior engine performance. By 1917, however, the overall demand for gasoline became so great that it was necessary to augment supplies by increasing the back-end boiling range. America entered the war at this stage and became the main Allied source of gasoline whose typical quality was 60 ON or less


Now with modern cars, most run on reg 87 fuel grades, only higher compression or turbo motors need premium to 91 octane or so. On my F-150 tow vehicle, mostly 87 but the manual says for tow haul use 89 for more boost. So most times am running mix of 87 and 89. But since all motor fuels have 10% ethanol, that lowers performance and milage so......use what your vehicle needs for how you run it!

[Charlie B in N.J.]

Watch the show Engine Masters. Season 6 Episode 2. Titled Does Octane Make Power? The guys test 87, 91, 110 and 116 octane fuel and the results are amazing. The increase in HP produces over that range was less than 5. Leads me to think that even if mixing different octane rated fuels increases octane the results in power would not be noticeable. Engine Masters can be seen on You Tube. It was one of the very best automotive shows on TV no contest. It was a spin off of the Roadkill shows on the Motortrend channel and in their infinite wisdom Motortrend cancelled the entire series a few months back.

[TRDxB2]

The reason for a low octane rating for a Model T as their low-compression engines (approx. 4:1) were designed for 40–60 octane fuel. Today's 87 octane is well above what would be considered "premium". Model T or Modern car engine, putting a higher octane fuel than recommended is pointless. Remember too that once started a Model T would run on kerosene. Its low octane rating, generally ranging between 20-50 back in the day.

Great article about Model T fuel https://modeltfordfix.com/what-kind-of- ... el-t-ford/

[TXGOAT2]

Octane rating does not indicate the level of available power in the gasoline itself. Octane rating is a measure of how the fuel mixture behaves during the actual combustion process in the engine cylinders. Lower octane rated gasoline may "detonate" "ping" or "knock" during combustion, usually when the engine is under load. The very low compression pressures in the Model T engine, even at full throttle at sea level, will come nowhere near creating detonation when using modern gasoline blends. There is no need to use "high octane" or "premium" gasoline in a Model T unless it is to take advantage of a superior additive package. The measure of fuel value of a gasoline is expressed in BTU units. Higher BTU fuels have more potential power per unit of volume, which the engine may or may not be equipped to realize. For instance, ethanol has about one half the BTU content of typical gasoline, but it has a high octane rating. For best power and economy, use a non-ethanol gasoline, or the lowest ethanol blend you can obtain, which is typically 10% ethanol, or E-10. The lowest octane rated fuel you can buy in the USA is more than sufficient for use in a Model T, including those with high compression heads. As for power, an E-10 blend might reduce your engine output by 3 to 5 % compared to a straight gasoline blend of equivalent BTU content. Higher ethanol blends will reduce power further. High octane gasoline is designed for high compression engines, especially those operating under heavy load. Many modern high performance engines can operate on "regular" gasoline will no ill effect other than somewhat reduced power at higher throttle levels.
The best commercially available gasoline for a Model T is regular grade Tier One gasoline, preferably ethanol-free, but any gasoline up to E-10 is fine. A T will run fine on higher ethanol blends, but power output will be reduced, and common issues related to ethanol will be increased. A Model T can be made to run fairly well on straight ethanol, but maximum power and fuel mileage will be substantially reduced.

[TXGOAT2]

Kerosene has a VERY low octane rating, but a high BTU content. Diesel is also a low octane, high BTU fuel.

[TXGOAT2]

There is no harm in mixing gasolines, but no reason to do so.

[Mark Gregush]

Lots of fuel sold back than was a 50/50 mix of kerosene and gas from the information I have come across.

[Mike Silbert]

When you buy mid octane grade fuel at the pump what happens is that the pump mixes the fuel from the low and high octane tanks underground.
That is done is to save installing another tank and hauling another truck out to deliver the mid grade fuel.
So to the original question the answer is that the manufacturers, distributors, and stations mix it so it will work for you.

But I ask why?
Todays fuel and additives and detergents are far superior to what you got back in the day except the alcohol and oxygenators added today.
We can debate about the effects of those for days.
The fuel you buy at the pump is the same everywhere since ALL the stations use the fuel from the pipelines that crisscross the country.
At the depot when they load it into the tankers and add their particular additive package it becomes a particular brand and goes to the different stations.
The octane only matters if the engine and vehicle can take advantage of it.
Since the Model T is not considered a High Performance vehicle what are you getting by spending more?
There is some validity to different additives and amount of alcohol differences in gas at the pump.
Personally I run standard pump gas 87 octane with different amounts of alcohol.
It also has the oxygenators in it that are required to be there most of the year.
Alcohol free gas is not anywhere near me without buying race gas in 5 gallon buckets at somewhere near $25/gallon.
I would prefer alcohol free it if were readily available.
My tank is sealed with a liner and I don't really have any issues, at least not yet.
The best solution is to keep the gas fresh by driving the car...

Here is what the "experts" say about the issue.
https://www.eia.gov/energyexplained/gas ... -depth.php
https://www.eia.gov/energyexplained/gas ... s-from.php
https://www.caranddriver.com/features/a ... e-charger/
https://www.sunoco.com/pit-stop/post/ma ... ctane-fuel

[TXGOAT2]

Gasoline quality was very low for several years due to exploding demand and to WWI. People were buying thousands of cars and demanding gasoline in greater volumes than refineries could produce it. There was far more kerosene than the shrinking kerosene market could consume, and less gasoline than the market was demanding. The amount of gasoline in a barrel of crude oil varies a lot, with some crude containing very little gasoline and other crude having a high gasoline content. The advent of catalytic cracking, a refining process that converts kerosene and related fractions of crude oil into gasoline, made good quality gasoline available in vast quantities. Later on, the development of tetra-ethyl lead anti-knock compound made high octane gasoline widely available at low cost, and made higher compression engines and great leaps in horse power and fuel efficiency practical. Compression ratios were raised substantially and engines were constructed to operate reliably at higher crankshaft speeds. The 177 cubic inch Model T engine developed about 20 HP at 1600 RPM, or about 1/10 HP per cubic inch of displacement. The similar, slightly higher displacement 200 CID Model A engine with a better design Ricardo combustion chamber made 40 HP at about 1800 RPM at about 5:1 compression. By the late 1930s, typical auto engines were making about 4/10 HP per cubic inch of displacement at 6:1 to 7:5 compression, and post WWII engines were making about 1/2 HP per cubic inch, and the early 1950's OHV engines did better than that with compression ratios moving to 8:1 and higher. The catalytic cracking process and the addition of "Ethyl Fluid" made it possible to make enormous amounts of high octane gasoline from substantially less crude oil than had been possible in the 1920s.

[tmodeldriver]

I just use the corn free gas from WAWA. The T Model seems to like it just fine. If it sits in the tank for a few months it doesn't spoil.

[TXGOAT2]

Burning food for fuel is absolutely absurd!

[TXGOAT2]

"On my F-150 tow vehicle.... towing..."

I'd put 93 octane in that vehicle when towing, especially when towing in hot weather or at low altitudes. For normal driving, 87/89 should be fine. Modern high output engines need high octane fuel for maximum performance and economy when operating at higher loads. The ECM is supposed to prevent damage from detonation by de-tuning the engine as needed to prevent detonation. It can only do so with some sacrifice in maximum power and economy when operating at higher average power demands, such as when towing or passing, etc. Running a modern high performance engine, such as a small displacement turbocharged engine , at high average loads on low octane fuel is probably false economy, since running the engine in a detuned state much of the time, with later than ideal spark timing and perhaps a richer mixture will reduce power and fuel economy while increasing stress on the engine.