I am getting ready to use my 97 F350 4x4 Crew Cab EFI 460, E4OD, 160,000 miles, to tow a 5500-6000 lb. RV from the flatlands of Oklahoma into southern Colorado right on the divide. I had a local here suggest that running premium fuel (90-91 octane) would actually save me money in the long run towing. He claimed the additional power from the higher octane fuel would translate in better economy and more than offset the extra cost for the fuel, especially in my higher mileage 460.

I thinks Tonto took one too many tokes on the ceremonial pipe, but then again...Can I get an opinion from you guys, the experts?

Many thanks,

 

If your truck runs better on the higher octane, you could come out ahead. I've heard it can be helpful at high altitudes, but I'm not sure.
If youa re set up for the cheap stuff, then it's a waste to buy the premium.

 

if you have a stock motor with stock compression, running premium won't do anything. you might even lose miles per gallon.

 

You don't need as much octane at higher altitude, go up to high altitude places like Laramie WY. (7200+ft) the regular there is only 85 octane as I recall.

But as for the original question, no high octane fuel doesn't give you more power, and infact actually can reduce power. If your engine "pings" or detonates under a hard load, then yes the higher octane is going to help you but if it doesn't have any issues with detonation then it's not an advantage.

One other thing you have an EFI, so as you are climbing up, about every 2500ft of altitude change you might want to either tromp the throttle to the floor real quick, or stop and shut the truck off for a minute then restart it. ford uses a BMAP (barimetric manifold air preasure sensor) when you do one of those 2 things the barimetric side of it takes a reading and recalibrates for any altitude changes

 

Let your ear make the decisions, assuming you can hear well. If you know what ping and knock sound like, choose the octane that runs quietly in your truck.

I have a 94 F250 460 that I use to tow an 8000# trailer. Normally I use 87 octane for no tow driving around tow stuff.

In cold weather I can usually get away with 87 octane even while towing.

While towing in hot weather and or lots of hills I use either 89 or 92 octane. Sometimes if I am being cheap I will have one tank with 89 and the other with 92 and switch to the 92 tank when I hit hills.

Basically what I am doing is listening to the engine for signs of ping growing to knock.

The engine computer has some ability to adjust timing for the octane and load. The range of adjustment is limited so using lower octane gas will narrow the ability of the computer to adjust. If the timing is retarded too much all the time, your gas mileage will suffer. Interestingly high octane fuel will also loose mileage since it is a bit harder to burn so it releases less energy in a proper burn. There is a fine balancing between octane being too high for mileage and too low causing retardation of the timing. At least this is some of the theory I have read over the years.

The general advice is run the gas that doesn't ping or just has a gentle ping under hard load and heat. This will give optimum economy in most cases. You do not want knock. Ping, knock and detonation are kind of the same beast but go from harmless to devastating, so it pays to know what each sounds like.

BTW, octane boosters usually require a lot to make a significant difference. It is cheaper to just use higher octane gas than to boost it. Been there done that.

Good Luck,

Jim Henderson

 

My carburated 460 doesn't seem to care either way so I won't waste my money on premium fuel. I don't know how the EFI's react to higher octane, but I assume the same. If its not pinging then don't waste the money.

 

Under high load, high heat conditions, if your engine temperature goes well above normal, switching to premium will help because when overheated, an engine that performs normally may go into detonation.

 

Best to use high octane from the get go here's why:
Most modern engines employ knock sensors which will retard the timing if it sences any knock, and when that happens you lose power and fuel economy. When fuel detonates instead of burns you also get extremly high temperatures and pressures that can damage your engine. The increased load will increase the tendency for it to knock but my point is why risk it for 20 cents more per gallon for this special trip. An important thing to remember is that 75% of knocking occurs without you hearing it. By the time you hear it it means it's severe and capable of bending a rod etc. Another benifit of higher octane is you wont be worrying about it.

 

Higher octane=LESS VOLATILE and LESS POWERFUL fuel

Run the lowest octane you can, if 87 is the recommendation use 87.

Diesel fuel has much more energy per gallon than gasoline, and is only give or take 50 octane. higher octane fuels resist ignition better than low octane fuels, allowing the use of higher compression and ignition timing advance. Ive towed 8000lb trailers with my 87 using regular(87) octane, with no pinging, that was over rough and hilly terrain with some need for 4wd L. if you have 2 tanks you could try the regular in one tank and premium in another method, then you'd see exactly what you need by monitoring your gas mileage on each tank.

 

You sir, must like wasting your money and dispensing wrong info. If there isn't enough compression to utilize the extra octane you're wasting you money for less gas mileage. If you are running your setup so close to the edge that it knocks all the time then you are again showing how stupid you can be. If you know anything you can hear the mildest ping if you know what to listen for. If an engine is "Knocking" and you can't hear it or feel it then you need to pay someone to do you tuneups.

 

And you Sir are subscribing to the common idea that knocking is like a light switch, either on or off, and if it's on you can always hear it-not true. Knocking builds progressively and in the early stages it is not audible. Add to that the fact that most vehicles after they get 40-50 K miles on them have increased their compression ratio a point from deposits on top of the piston and there is your increased compression. Did you ever wonder why new cars dont knock but older ones do? You dont need to run your setup "close to the edge" to get knocking. Common in tune street vehicles do it all the time. Sure, compression is the major factor, but many things contribute to start an engine to knock-throw in a lean air fuel ratio or a glowing spark plug deposit and you can start a near stone cold no load engine to knock. Another factor is the crappy gasoline we get-refined so close to the bottom requirements that as soon as an engine gets even a little out of spec it drifts toward ping/knock. I could go on and on but the point is higher octane is more heat resistive. Compression is heat. Towing a load adds even more heat and you can start to see why regular gas frequently cant cut it. As far as tuneing engines go, I have several thousand under my belt. Don- FAA Engine Inspector/troubleshooter

 

Geez, low rpm airplane motors, wow I'm impressed. Lets see airplane gas, what?, 80 octane and 100LL? (yeah, I even dabbled in airplanes for a while), which isn't real bad stuff but you deal in air cooled motors and these are water cooled. Different beasts. Maybe that's why 2 strokes use different oil for air cooled and water cooled motors. Try a 2 liter, 8600 RPM race motor on a 16 foot tunnel boat (132 mph on the water is damn fast) or a couple of 502 BBCs turning 6800 in a 31foot offshore racing cat or maybe a 428CJ Ford turning 6500 in a 3500# race car. Ping and Knock, not the same creature, why must you guys lump them together? Different causes. I've been towing heaving loads with BB Fords for 35 years and Gee, I never lost and engine yet. Sure heat is a problem, but rather than use octane, just make it abit richer and that will solve the problem, cheaper too. Also if the water cooled motor starts overheating more than 20° or so while towing you need to upgrade the cooling system (More fan blades, more radiator cores, etc.). If the chamber is getting a little warmer try a 2 stage power valve. Unless you have the base compression to require the higher octane you are wasting your money.

 

Oh yeah, new cars don't knock because of knock sensors that back off ignition timing. So gee, if you are knocking when towing back off on the timing, that's a lot cheaper that premium gas. A recurved dist. will usually solve this anyway.

 

Well guys, you don't have to compare credentials if you make a good argument. The fact is, ping, knock, dieselling, detonation, whateveryacallit, are all related and come from various source causes. If all is well with the engine in quesion you won't have any of it. But, higher octane gasoline will give you a little margin of safety if something goes awry on the road. That it should be guarded against goes without saying because once it begins it is a negative spiral, driving the engine into overheating which exaggerates the problem and can lead to catastrophic failure if it is not attended to.

That said, as the altitude increases octane requirement drops, as MB pointed out. Going back to the original question, a 97 460 is EFI, right? It should have knock control built in. My conclusion would be that the benefit of running higher octane would possibly give him a little more power climbing those mountains in high heat conditions with the computer controlling the timing.

 

If you back off on your timing it may be cheaper but then your stuck with worse gas mileage and performance all the time, not just for towing. His original question made it sound like it was a special tow cross country. My point about knock sensors is most modern cars have them and they still have them when their old but they knock anyway right? So why dont they knock when their new? Cause the pistons havent had a chance to develop that layer of deposits that raise the compression ratio a point. If a car comes out of the factory at 8.5 after it gets 30/50 K on it it will be at 9.5 and thats when people start to use 89 octane instead of 87 but they really dont know why it's happening. Auto manufacturers and oil companies work together and formulate fuel to new car specs-they dont worry about what happens later to guys like us. As far as auto engine/aircraft engine, yes the cooling system is different, but the principles and issues are the same, except when an aircraft knocks it can blow the cylinder off and people die, so they do the right thing and give us 100 octane. There is even a method to blast the tops of pistons with walnut shells to remove the deposits and lower the compression ratio for aircraft engines. And Bear, I see you and I are about the same age so you might probably remember the Chevron white pump 100 octane so many years ago and we didnt have the problems we have now. The problem is really the fuel but most of the younger guys dont have the long range perspective. Engineers compare knocking to hitting the top of the pistons with a sledge hammer. If I hear my engine start to ping I stop it right away-downshift, fuel additive, whatever it takes. Yes I know some say light pinging is Ok but I dont want anything bad happening in my engine. Kinda like saying just a little bit of arsenic wont kill you. As far as the guys original question, OK, start off on regular and if you hear anything at all put an additive in it then switch to 92 for the rest of the tow. My own choice for towing is to do it from the get-go.