# Higher Octane Fuel Or Wasteful Spending?



## letscamp (Jan 22, 2010)

*Do you use higher Octane fuel or Additives when towing? *​
Higher Octane alone28.33%Higher Octane and additive 00.00%Additive alone00.00%Regular fuel alone2291.67%


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## letscamp (Jan 22, 2010)

I just Posted a reply in another topic referring to towing. I said at the end of the post that I had tried the higher octane fuel a while back when towing up hills and noticed nothing but less money in my checking account.

I'd like to get some input form everyone about what you use and or add to your fuel when towing, after an oil change, etc?
What was your outcome?
Cost to benefit?
Did it work or was it a waste?

I'm looking forward to what other use or think...


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## Nathan (Jan 2, 2007)

Ok, here's the deal.

It Depends......

Older vehicles did not adjust for octane rating in the fuel. Newer ones do (Not certain if your 07 does, but I don't think it does). Interestingly enough also on the new Ford's IF they are E85 capable, they will run at higher performance levels if running on E85. The downside will be a 30% reduction in fuel economy and more frequent maintenance required, but IF you have an E85 equipped Ford and want the max power for the hills, it is an option....


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## mmblantz (Jul 1, 2007)

I've tried towing with super but I end up getting about 8-9mpg either way so its a waste to me. ---Mike


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## ftwildernessguy (Oct 12, 2009)

Ford says it doesn't matter with my F150. I have tested it myself and get 1-2mpg more with higher octane. With the cost difference, it isn't worth it anyway, so I just use regular.


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## Nathan (Jan 2, 2007)

Oh yeah, I don't think you are going to see a measurable gain in fuel economy....

I was refering to power output.


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## MJRey (Jan 21, 2005)

Whether or not you get better performance or mileage is a big "It depends". Most vehicles will see no benefit from premium fuel. If you have an engine that adjusts the timing etc. based on knock and other sensors then you can get a bit more performance with higher octane. The improvement is from being able to run the engine closer to the the point where knocking occurs and thus getting a bit more efficient combustion.

It's also important to note that octane rating is not related to the fuels energy content. It's possible to have a higher octane fuel with lower energy content depending on the additive used to raise the octane rating. It's the energy content and combustion efficiency that primarily determine your mileage.


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## Joe/GA (Aug 14, 2009)

I had a Ford Mechanic tell me not to run premium because it would cause an increase of carbon build in the motor. I dunno! Anyway, I always use regular.


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## luverofpeanuts (Mar 9, 2010)

Joe/GA said:


> I had a Ford Mechanic tell me not to run premium because it would cause an increase of carbon build in the motor. I dunno! Anyway, I always use regular.


I always ran 92/93 octane in my '97 Expedition. I didn't notice any different fuel mileage....but then I never really tracked that. The reason I ran it is because it "felt" just a tad more responsive than on '87. The easiest place to feel that was on some long slow inclines that I frequently traveled On 92/93...I held speed w/o downshifting. On '87, it felt like it had to downshift.

Even if it was just a feeling... it was worth it to me, so I continued to run premium.


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## DocDzl (Apr 24, 2010)

Tried higher octane occasionally with the old 4.6L Expedition (and long before that with the even older Chevy C10 350ci). Also ran a tank thru with the new Tundra. No apparent difference except the total amount due on the gas pump.

Happy Camping!

Carl & Margo
Atlanta, Georgia


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## fshr4life (Feb 7, 2009)

There is a common misconception that premium gasoline has more 'energy' in it and that's the difference between the three grades available at most gas stations. That's not really true. While there may be some tiny, completely negligible difference in energy content, the big difference is the octane level. Octane is actually a rating of how hard it is to get the gasoline to ignite, NOT how much energy is in it. The higher the octane, the more compression it can withstand before spontaneously igniting. This is why the high-compression engines in many sports cars require premium fuel. (Those cars can get better thermal efficiency and power out of the gasoline due to their designed-in higher compression ratios, not due to the actual energy content of the gas itself.)

Now, in your average car or truck, its engine's compression ratio is set up for regular gasoline by the engineers who designed it, so putting premium in it doesn't do anything really. It still ignites at the same time with the spark and provides the same amount of energy. There is really only one time when you should upgrade to a higher octane level, and that is if you are experiencing engine knock. If the gasoline ignites prematurely before the spark fires, you get engine knock. You can hear the pistons making a 'clinking' sound. It can damage the engine over time. This happens more often when engine temps are high (say in the summer when you're towing up a big hill). If you hear your engine knocking, you should upgrade the octane to the next higher level until it stops. Otherwise, running premium in a vehicle designed with a compression ratio for regular unleaded is pretty much a waste of money. I don't know of any variable compression engines on the market yet that would change that. I think Honda is working on one, but it's not out yet and I'm sure it won't be in a TV when/if it does come out. So if your truck says to run regular gasoline, then just run regular gasoline unless it's knocking. In addition, almost all new engines now have a 'knock sensor' that can retard spark timing to reduce or eliminate engine knocking even on low grade gas towing up a hill in the summer. Just my 2 cents as a mechanical engineer...

JD


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## Nathan (Jan 2, 2007)

fshr4life said:


> There is a common misconception that premium gasoline has more 'energy' in it and that's the difference between the three grades available at most gas stations. That's not really true. While there may be some tiny, completely negligible difference in energy content, the big difference is the octane level. Octane is actually a rating of how hard it is to get the gasoline to ignite, NOT how much energy is in it. The higher the octane, the more compression it can withstand before spontaneously igniting. This is why the high-compression engines in many sports cars require premium fuel. (Those cars can get better thermal efficiency and power out of the gasoline due to their designed-in higher compression ratios, not due to the actual energy content of the gas itself.)
> 
> Now, in your average car or truck, its engine's compression ratio is set up for regular gasoline by the engineers who designed it, so putting premium in it doesn't do anything really. It still ignites at the same time with the spark and provides the same amount of energy. There is really only one time when you should upgrade to a higher octane level, and that is if you are experiencing engine knock. If the gasoline ignites prematurely before the spark fires, you get engine knock. You can hear the pistons making a 'clinking' sound. It can damage the engine over time. This happens more often when engine temps are high (say in the summer when you're towing up a big hill). If you hear your engine knocking, you should upgrade the octane to the next higher level until it stops. Otherwise, running premium in a vehicle designed with a compression ratio for regular unleaded is pretty much a waste of money. I don't know of any variable compression engines on the market yet that would change that. I think Honda is working on one, but it's not out yet and I'm sure it won't be in a TV when/if it does come out. So if your truck says to run regular gasoline, then just run regular gasoline unless it's knocking. In addition, almost all new engines now have a 'knock sensor' that can retard spark timing to reduce or eliminate engine knocking even on low grade gas towing up a hill in the summer. Just my 2 cents as a mechanical engineer...
> 
> JD


True, but Mark's also right that some new engines will advance the spark toward the knock limit, not just retard it if you are knocking... This is what allows you to get slightly more power with premium. Sure changing compression ratio would be even better, but as noted, that's not a currently available technology.


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## luverofpeanuts (Mar 9, 2010)

Nathan said:


> True, but Mark's also right that some new engines will advance the spark toward the knock limit, not just retard it if you are knocking...


It was discussed numerous times on an Expedition forum I follow that the Ford Triton engines....that debuted back in the '97 models did advance the the spark. I believe it is a fairly minor advance compared to what putting a "chip" in the engine would do.


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## fshr4life (Feb 7, 2009)

Nathan said:


> There is a common misconception that premium gasoline has more 'energy' in it and that's the difference between the three grades available at most gas stations. That's not really true. While there may be some tiny, completely negligible difference in energy content, the big difference is the octane level. Octane is actually a rating of how hard it is to get the gasoline to ignite, NOT how much energy is in it. The higher the octane, the more compression it can withstand before spontaneously igniting. This is why the high-compression engines in many sports cars require premium fuel. (Those cars can get better thermal efficiency and power out of the gasoline due to their designed-in higher compression ratios, not due to the actual energy content of the gas itself.)
> 
> Now, in your average car or truck, its engine's compression ratio is set up for regular gasoline by the engineers who designed it, so putting premium in it doesn't do anything really. It still ignites at the same time with the spark and provides the same amount of energy. There is really only one time when you should upgrade to a higher octane level, and that is if you are experiencing engine knock. If the gasoline ignites prematurely before the spark fires, you get engine knock. You can hear the pistons making a 'clinking' sound. It can damage the engine over time. This happens more often when engine temps are high (say in the summer when you're towing up a big hill). If you hear your engine knocking, you should upgrade the octane to the next higher level until it stops. Otherwise, running premium in a vehicle designed with a compression ratio for regular unleaded is pretty much a waste of money. I don't know of any variable compression engines on the market yet that would change that. I think Honda is working on one, but it's not out yet and I'm sure it won't be in a TV when/if it does come out. So if your truck says to run regular gasoline, then just run regular gasoline unless it's knocking. In addition, almost all new engines now have a 'knock sensor' that can retard spark timing to reduce or eliminate engine knocking even on low grade gas towing up a hill in the summer. Just my 2 cents as a mechanical engineer...
> 
> JD


True, but Mark's also right that some new engines will advance the spark toward the knock limit, not just retard it if you are knocking... This is what allows you to get slightly more power with premium. Sure changing compression ratio would be even better, but as noted, that's not a currently available technology.
[/quote]

Yes, that is absolutely true. But even for those vehicles with a computer that will advance the spark with premium fuel, they will probably see less than a 1% or 2% or so increase in power which is more than offset by the extra cost of the fuel. Again, the compression ratio isn't changing, so you're not going to see much of an increase in power by advancing the spark timing. It's pretty much negligible given the higher price you'll be paying.

JD


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## letscamp (Jan 22, 2010)

So far I like what i'm hearing! Stick with the good time tested regular. Thanks fshr4life for making sense of what seems like an easy question but turned out to be much more deep.

Are those bottles of octane boosters you see at auto part stores the same concept as higher octane fuels? Those seems to sell like hotcakes! From what I have been hearing they seem just as useless. I don't see how a 12oz bottle could even raise a 25 gallon tank of gas up from 87 to 91.


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## fshr4life (Feb 7, 2009)

I'm not a chemist, so maybe someone else can chime in on this, but from what I've seen, many octane boosters are snake oil. They say things like "raises your octane by up to 5 points" on the bottle which means that it could be anywhere from 0-5 points (probably closer to 1 or 2) and the company that sells it is still covered. I've seen some scientific tests that showed increases on premium 91 octane fuel up to only about 92 or 93 octane with some of the best octane boosters out there. If you really want to boost your octane, you could add straight toluene to your fuel and effectively turn it into race fuel. You could get your octane up to 100 doing that, but at the levels of toluene you would need, it would start damaging your emissions equipment, spark plugs, etc. But like I said before, raising your fuel to that level of octane is totally pointless unless you're putting it into an engine that is designed to make use of it by having a really high compression ratio. So, even if the off-the-shelf octane boosters work perfectly and give you 100 octane race fuel, there's not much point in paying to run that higher octane in your TV unless your engine is knocking or unless your vehicle is set up to adjust the spark timing and you just gotta have that extra 2 or 3 horsepower.

Quite frankly, if you just slow down a couple miles per hour when you're towing and make sure your tires are properly inflated, you will reduce your horsepower requirements much more than a bottle of octane booster could give you. The force of drag created by the wind is based on the speed of the air moving over your rig SQUARED, so the force your TV has to overcome increases EXPONENTIALLY as you drive faster. I'm sure you've all seen that if you drive 55mph, you get much better mileage than if you drive say 60 or 65mph. That's because you're right at the point where the force of drag is making it's exponential upwards climb. So your speed (and whether you have a head wind or tail wind) is a much larger factor on how much power (and fuel) you need to pull your trailer.


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## Nathan (Jan 2, 2007)

fshr4life said:


> Quite frankly, if you just slow down a couple miles per hour when you're towing and make sure your tires are properly inflated, you will reduce your horsepower requirements much more than a bottle of octane booster could give you. The force of drag created by the wind is based on the speed of the air moving over your rig SQUARED, so the force your TV has to overcome increases EXPONENTIALLY as you drive faster. I'm sure you've all seen that if you drive 55mph, you get much better mileage than if you drive say 60 or 65mph. That's because you're right at the point where the force of drag is making it's exponential upwards climb. So your speed (and whether you have a head wind or tail wind) is a much larger factor on how much power (and fuel) you need to pull your trailer.


And some times common sense is just no fun at all!

It's still a good idea though......


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## Red Beard (Feb 13, 2010)

Although I completely understand the science of the fuel and the mechanics of an engine, I run 91-92 when towing. I found that I can pull the hills a little better. I also noticed that I have better throttle response.


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## fshr4life (Feb 7, 2009)

Nathan said:


> And some times common sense is just no fun at all!
> 
> It's still a good idea though......


Nathan,

I heard that! I'm definitely not going to say that I drive 55mph all the time when I'm towing. Just because we know the physics doesn't mean we abide by the rules. I just can't keep off the throttle on my new diesel. I also guess my ego starts to get the best of me when I see another TT coming up behind me









JD


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## Collinsfam_WY (Nov 9, 2006)

Back when I had my '02 F150, I tried it several times and could tell no difference with power or mileage. With the V10 though, I fill up with the 91 oct. fuel, load up the 91 performance/tow program from 5 Star Tuning and the power just rocks. MPG is also up by 2-2.5mpg which with a V10 and the weight/size of a Superduty vs. an older F150, is surprising and also put a very big smile on my face.

-CC


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## AKF150LARIAT4X4 (Sep 14, 2005)

X2 on EVERYTHING Fshr4life said!


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## fshr4life (Feb 7, 2009)

AKF150LARIAT4X4 said:


> X2 on EVERYTHING Fshr4life said!


Nice Truck! How do you like the 2010?

JD


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