High test gasoline shows increase performance

[pecheux]

Good day. Here is an experimentation I did almost accidentaly. Took my small fishing rig out 2 days in a roll, same weight, same river, same distance, ect. The first day I had a tankfull of hight test gas and the second day a fresh tankfull of 81 octane regular gasoline. In oposition of everything I have read on Iboat ... I notice some difference in performance. With Hightest I notice a small but noticable increase in rpm, top speed, and hole shot. (but rougher idle) I sometime switch from hightest to regular depending if I fill the SUV at the same time or not, and never realy notice any difference but I also very seldom go out on the river more than once every other week. Going out there two days consecutively made it easy to have performance fresh on my mind. The motor is a Force 15 hp. Has anybody else see a difference using hightest gasoline ? Tx

 

[ondarvr]

Re: High test gasoline shows increase performance

Your motor doesn't have the ability to make adjustments and take advantage of a higher octane fuel. Do you have a tach and GPS to confirm the slight difference in RPM and speed?

There is a real possibility that there was an actual difference in how it performed with two different tanks of fuel, this can happen even if both were 81 octane. If one was E-10 and the other was E-0 there would be a difference in performance that you may be able feel, but it would have nothing to do with the octane rating. You would never know if this was the case unless you tested both tanks at the time you filled up.

The ethanol content in fuel changes frequently as they refill the tanks at the station, sometimes it's well below 10% and other times it goes over 10%. This will change the power output of the engine.

 

[foodfisher]

Re: High test gasoline shows increase performance

Engine manufacturers recommendations? Could be a placebo effect.

 

[JB]

Re: High test gasoline shows increase performance

A change in barometer, humidity and air temp could cause minor changes, Pecheux.

BTW: Congratulations on reaching 1K posts.

 

[robert graham]

Re: High test gasoline shows increase performance

When I was in my teens, I had a 3HP, 2 stroke moped, and it would definitely rev higher on the old Amoco White gas than any of the other gas I tried. That said, I still run 87 octane regular in my 90C Yamaha. If you're gettin' more RPM's/Power from the high test gas, then go for it! Good Luck!

 

[Philster]

Re: High test gasoline shows increase performance

It's possible the tuning /design of the Force is positioned to enjoy premium a bit more than regular, wherein premium's higher octane just happens to ignite at a slightly more optimal point in the stroke and work better with the timing, compression etc. Regular is fine and within parameters for not knocking, but maybe -- just maybe -- that premium was just a little better in synch with the engine.

I'm not ruling it out. However, I am ruling out your 'test'. It's anecdotal and there are too many variables. I am also ruling out the possibility that anyone can chime in and declare it impossible.

One thing we DO know about high-test gas: If you use it in a sentence, we have a general idea of how old you are.

.

 

[robert graham]

Re: High test gasoline shows increase performance

It's possible the tuning /design of the Force is positioned to enjoy premium a bit more than regular, wherein premium's higher octane just happens to ignite at a slightly more optimal point in the stroke and work better with the timing, compression etc. Regular is fine and within parameters for not knocking, but maybe -- just maybe -- that premium was just a little better in synch with the engine.

I'm not ruling it out. However, I am ruling out your 'test'. It's anecdotal and there are too many variables. I am also ruling out the possibility that anyone can chime in and declare it impossible.

One thing we DO know about high-test gas: If you use it in a sentence, we have a general idea of how old you are.

.

Well, we did call it "High Test"...first gas I pumped was at a Texaco station with a hand pump up into a grduated clear glass cylinder with markings on it for each gallon....long time ago!

 

[pecheux]

Re: High test gasoline shows increase performance

A change in barometer, humidity and air temp could cause minor changes, Pecheux.

BTW: Congratulations on reaching 1K posts.

Thank you JB, I had forgotten about these factors. It was in fact a much warmer day when I used the regular gasoline. Could that have made the lower octane gas less powerfull ?

 

[pecheux]

Re: High test gasoline shows increase performance

It's possible the tuning /design of the Force is positioned to enjoy premium a bit more than regular, wherein premium's higher octane just happens to ignite at a slightly more optimal point in the stroke and work better with the timing, compression etc. Regular is fine and within parameters for not knocking, but maybe -- just maybe -- that premium was just a little better in synch with the engine.

I'm not ruling it out. However, I am ruling out your 'test'. It's anecdotal and there are too many variables. I am also ruling out the possibility that anyone can chime in and declare it impossible.

One thing we DO know about high-test gas: If you use it in a sentence, we have a general idea of how old you are.

.

Thank you for your comment. Yes I suspect hightest may have more benefit with a Force motor. Back when my dad owned a car dealership hightest gas was simply called RED and regular YELLOW because that was their individual color ... LOL (now you know my age ... LOL ) and Red sold for 0.26 Cents/gallon and Yellow 0.23 C/gallon. Cheers

 

[BonairII]

Re: High test gasoline shows increase performance

It was in fact a much warmer day when I used the regular gasoline. Could that have made the lower octane gas less powerfull ?

Yes. Cold air is more dense and oxygen rich.

 

[pecheux]

Re: High test gasoline shows increase performance

Engine manufacturers recommendations? Could be a placebo effect.

Nope ... I dont buy the placebo effect. Was born and raised in family garage environement and can tell + or - rpm without a tach. But I dont rule out exterior factors that may have been the cause. Cheers

 

[Philster]

Re: High test gasoline shows increase performance

Engines lose power when it's warm and warm/humid makes it even worse.

I am 45. My dad always said high-test. But by the time I was pumping gas into my moped or 2-stroke Evinrude, it was called 'super', then the major brands 'round these parts stuck with 'premium'.

However, I did carry over one term for the longest time, even though it was a thing of the past. I would say 'regular unleaded' to distinguish from 'regular'. I use to pump 'regular' (good old leaded stuff) into the moped and boat, but cars were only to get 'regular unleaded'.

After lead was gone and pretty much forgotten, I kept saying "regular unleaded''. Now I just say regular, but it took me a while.

 

[Sea Rider]

Re: High test gasoline shows increase performance

I'll second what Pecheux states. Most engines can run on minimum octane fuels, but most outboard owners manuals recommends the use of higher ones. My engine is rated for 90 ninimum, but always use 95 unleaded E8 fuels, find that has instant hole shot response, need less throttle aceleration while on plane and lasts bit longer than when using 90. The price difference is so small that on portable engines will be nonsense saving cents per gallon. In my particular case a 5 octane difference makes all the difference.

Happy Boating

 

[pecheux]

Re: High test gasoline shows increase performance

I'll second what Pecheux states. Most engines can run on minimum octane fuels, but most outboard owners manuals recommends the use of higher ones. My engine is rated for 90 ninimum, but always use 95 unleaded E8 fuels, find that has instant hole shot response, need less throttle aceleration while on plane and lasts bit longer than when using 90. The price difference is so small that on portable engines will be nonsense saving cents per gallon. In my particular case a 5 octane difference makes all the difference.

Happy Boating

Thank you for your support ...LOL Actualy 10 years ago an old friend who was an Ex Mercury dealer, and who was also my outboard motor mecanic, told me I should use 91 octane (hightest) gasoline at all times. According to him gasoline's quality was on a downward trend. Now just 2 weeks ago the senior mecanic from our local and major Mercury dealership told me the exact same thing.

Furthermore my 4 cyl SUV that should use 87 octane fuel happens to run better and show bigger horses when fueled by 91 or 94 octane fuel. Now what is the old saying ??? no smoke without a fire ??? or something like that .. LOL Cheers

 

[ondarvr]

Re: High test gasoline shows increase performance

Things are getting mixed and confused.

Your SUV has fuel injection and a computer to adjust the settings and take advantage of higher octane fuels, it in no way equates to increased performance in an old school O/B.

Merc and a few other outboard manufactures have specific motors that should run higher octane fuel and it says so in the manual, the vast majority of motors are designed to use the cheap stuff though, just check your manual.

In some parts of the world you can't always trust the fuel being supplied is all it should be, so maybe running a higher octane is good insurance if the quality is in doubt.

The facts are your typical old school outboard is not going run better or make more power with a higher octane gas than it was designed to use.

 

[Philster]

Re: High test gasoline shows increase performance

You're mixed and confused.

Older outboards don't have electronics that retard ignition and manage other things to make an engine act like it's always running on 87 octane, even when 91 is pumped in. That's what most EFI systems do: they make an engine run on the least expensive gas so darn well that there is nothing to gain by running higher octane. The whole system works best this way. Cost of operation is lower and emissions are rock solid, and you don't need a high compression engine to get power. An old outboard CAN take advantage of higher octane fuel IF it can, because nothing is blocking it from happening. If the ignition is best with higher octane, then that is what happens. it improves and you get a little power in return from the better timing of the more resistant higher octane fuel.

In an old outboard, it's one of the least surprising results.

 

[ondarvr]

Re: High test gasoline shows increase performance

You're mixed and confused.

Older outboards don't have electronics that retard ignition and manage other things to make an engine act like it's always running on 87 octane, even when 91 is pumped in. That's what most EFI systems do: they make an engine run on the least expensive gas so darn well that there is nothing to gain by running higher octane. The whole system works best this way. Cost of operation is lower and emissions are rock solid, and you don't need a high compression engine to get power. An old outboard CAN take advantage of higher octane fuel IF it can, because nothing is blocking it from happening. If the ignition is best with higher octane, then that is what happens. it improves and you get a little power in return from the better timing of the more resistant higher octane fuel.

In an old outboard, it's one of the least surprising results.

I may not have understood what you just stated.

Older outboards have fixed timing, so unless you manually adjust it, there is no change in the setting. So it runs the same on any octane fuel when set at the factory spec, you can manually advance it though, which may or may not do anything to increase power.

Newer EFI engines can adjust the settings as the sensors in the system let the computer know what's going. They do not lower the bar to the lowest grade of octane like an older type if ignition and keep it there. It will immediately adjust each cylinder to perform at its best independently from the others. This means you ?may? see (feel) a difference between low and high octane fuel, I say may because it?s possible you won?t feel the small difference.

 

[pecheux]

Re: High test gasoline shows increase performance

IMHO It just may be that gasoline quality now a days is lower than it used to be and irregular in it's content.

 

[Philster]

Re: High test gasoline shows increase performance

I may not have understood what you just stated.

Older outboards have fixed timing, so unless you manually adjust it, there is no change in the setting. So it runs the same on any octane fuel when set at the factory spec, you can manually advance it though, which may or may not do anything to increase power.

Newer EFI engines can adjust the settings as the sensors in the system let the computer know what's going. They do not lower the bar to the lowest grade of octane like an older type if ignition and keep it there. It will immediately adjust each cylinder to perform at its best independently from the others. This means you “may” see (feel) a difference between low and high octane fuel, I say may because it’s possible you won’t feel the small difference.

Begging the question abounds.

The fixed timing might be set such that the whole system operates better on higher octane fuel. Unfortunately, that's the reality against your argument.

I am not saying the OP got results from the octane change; I am saying that in an older non-EFI engine, you can bet your hat that there are going to be engines that benefit from higher octane, because they are going to work better with the timing.

 

[Sea Rider]

Re: High test gasoline shows increase performance

The thread was entirely about 2 strokes 15 HP engine, this statement can be applied to new 2 strokes also. Computarized outboards are completely different animals. Been reading that E fuels lowers octane ratings by 2, so a 87 could be really a 85 and so on. That's why using higher octane fuel would be advisable, and besides, higher octane have better cleaning aditives than lower octane fuels, will keep pistons, plugs much cleaner in case you don't use periodically carbon guard or products that mixes on tanks.

Happy Boating