I was using 93 octane in my 2005 frontier ever since I purchased it (about 5 tanks) and I got 17.5 - 17.8 mpg on every tank. This time at fill up I decided to use mid grade instead so I mixed 10 gal of 93 with 9 gal of 87. On this tanks my mpg is 18.9? What could explain this? Freak weirdness or is mid grade a better mileage fuel?
Is this possible? +1.4 mpg gain
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I don't have much knowledge of how octane and fuel economy work, but I wouldn't draw this conclusion just yet, wait until you get another 4-5 tank fill-ups and then you can make a better conclusion. If they are all around the 18.9-19 part, then you will know that you made some improvement with that.
What octane does your Frontier call for?
What octane does your Frontier call for?
Lower Octane means a faster burning fuel. You may be getting better fuel economy because you are getting more complete combustion, especially if your vehicle is designed to run on 87 instead of 93.
If you are running 93 for the extra "cleaning", you would be better off running the octane your vehicle requires and adding FP60 for the extra cleaning and lubricating qualities.
If you are running 93 for the extra "cleaning", you would be better off running the octane your vehicle requires and adding FP60 for the extra cleaning and lubricating qualities.
Yeah, not a valid sample, in my estimation. But t could be pointing you in the correct direction. Keep it up, run a detergent/UCL now and then (if you wish) and see where it goes. I have been educated that the potential energy in lower octane fuel is greater. Now the question is, is there enough of a difference for you to see in YOUR vehicle? There have been a few examples in my experience where a vehicle supposedly designed to operate on 87 actually improved it's operation on a higher octane fuel. 4.6l engines in Cr. Vic's and LS Magnum engines in Dodge trucks come to mind. As well, I noticed an improvement in acceleration in LT-1 Caprices with high octane fuel but no efficiency increase. My current Hemi Ram does not seem to prefer higher octane fuel even though DC advises to use 89. My understanding is that this engine will allow for more advance with better fuel but only up to a point. I do not think that I have used it enough to see a real world difference in all honesty. Time will tell.
John.
John.
You need a chemical engineer to weigh in on this one. My understanding is that there is more energy in the lower grades of gasoline, and my anecdotal evidence from buying Shell premium at the same price as regular a couple of years ago supports this. I didn't notice a change in performance, just mileage.
My son, who is an ME, explained that the higher grades have more octane, while the lower grades have more heptane (I hope I am getting this right). The heptane has more energy per gallon in it because of the way the chemical bonds form.
Therefore, the mileage gain is possible.
I also understand all grades of gasoline have the same amount of detergent in them. I don't know if its true, but I only use regular and I use injector cleaner or complete fuel system cleaner about 500 miles before each oil change. I also do not buy gas at AM/PM.
Don
My son, who is an ME, explained that the higher grades have more octane, while the lower grades have more heptane (I hope I am getting this right). The heptane has more energy per gallon in it because of the way the chemical bonds form.
Therefore, the mileage gain is possible.
I also understand all grades of gasoline have the same amount of detergent in them. I don't know if its true, but I only use regular and I use injector cleaner or complete fuel system cleaner about 500 miles before each oil change. I also do not buy gas at AM/PM.
Don
Beercan- Wait for a larger sample size to make any conclusions. May just be the direction of the wind...
JaxRX8- Octane refers to the tendency to pre-ignite. It does not refer to the rate at which the combustion propagates. Octane is NOT a measure of how fast the fuel burns.
Cicero- Octane is NOT a measure of energy content. Lower octane does NOT have more energy.
JaxRX8- Octane refers to the tendency to pre-ignite. It does not refer to the rate at which the combustion propagates. Octane is NOT a measure of how fast the fuel burns.
Cicero- Octane is NOT a measure of energy content. Lower octane does NOT have more energy.
GMorg, I assume you have a scientific basis for that statement. Hydrocarbon fuels comes in various grades and the name indicates the number of carbon atoms. Methane has one, then you go on up, propane, butane, heptane and then octane has eight carbon atoms. Acetylene has a more complex bond and therefore more energy. I learned that much before I switched my major from chemistry to accounting.
In gasoline the octane rating (note that word rating) refers to the resistance to detonation. Refiners achieve the desired octane rating by blending. Alcohol will raise the octane rating, but contains less energy than octane. Heptane will lower the octane rating, but contains more energy than octane. Gasoline made out of pure octane will have a higher resistance to detonation than a gasoline made of a blend of heptane and octane. Then there are additives like tetra-ethyl lead.
As I said, I would really prefer that a chemical engineer or otherwise truly qualified person would weigh in on this.
Don
In gasoline the octane rating (note that word rating) refers to the resistance to detonation. Refiners achieve the desired octane rating by blending. Alcohol will raise the octane rating, but contains less energy than octane. Heptane will lower the octane rating, but contains more energy than octane. Gasoline made out of pure octane will have a higher resistance to detonation than a gasoline made of a blend of heptane and octane. Then there are additives like tetra-ethyl lead.
As I said, I would really prefer that a chemical engineer or otherwise truly qualified person would weigh in on this.
Don
Cicero17- Perhaps I should re-word my comment. Lower octane does not mean lower or higher energy content. However, it does not exclude lower or higher energy content. By the way, my degrees are in biochemistry and genetics - not chemical engineering.
Off topic but Beercan why didn`t you just pump the 89 octane and let the pump mix it for you?(or did this gas station only have two grades)
Because as stupid as it sounds I hate getting ripped off for 1 octane. If you think about it 89 is not really mid grade. It is mid grade -1. It is a marketing scam I refuse to participate in so I make my own mid grade for the same price and get an "extra" octane rating.
I think I will try this out for a few tanks. I suspect that I will see this level out back down into the 17.5 range. Sure would be nice if it stayed though
GMorg is right on the money. Aviation 100LL (99RM/2 )burns slower than the racing gasoline equivalent. Octane is an independent variable from burn speed, specific energy, etc.
Stop it! You are hurting their brains! They might not recover!
My wifes Lexus RX-300 is the first vehicle that we've ever owned that actually gets better MPG on 93 octane fuel. I've tried different octane rating fuels in all of my vehicles over the last 30 years and they all got worst MPG with higher octane fuel as compared to the 87 octane. For the 1st 5 years of use on her Lexus, I used only 87 octane. The owners manual states, 87 or higher for normal usage and 91 or higher for better performance. On 87 octane, the vehicle barely get the EPA estimate of 18 city. Just a notion caused me to try 91-93 octane in this car. The engine just seems to get consistantly better MPG on the higher octane fuel.(High 19's-Low 20's). No other modifications or tune ups. I have been measuring my MPG on all of my vehicles on just about every tank of gas over the last 30 years. This is just something that I like to do. Heres another thing! This vehicle has the MPG on the NAV Screen. And I always compare my acutal results(using a calculator)with what the MPG listed on the Nav screen. They are quite close, within a couple of 1/10's. What I have noticed most is that when I get into the throttle more heavily, I can watch the MPG decline on the Nav screen but, it seem to recover much faster than ever, back to better fuel economy when I start to drive with a lighter foot again. Where as with the 87 octane fuel and a heave foot, the MPG never recovered this quickly. And no, Im not driving any easier these days. Go figure!
If an engine really needs higher octane to perform at its maximum potential but lower octane fuel is used the knock sensor will retard the timing to prevent detonation.A little more throttle is needed to achieve the same performance therefore using more fuel.Using higher octane that needed is a waste of money but some facts need to be considered,even if the owners manual claims 87 octane over time deposits can increase the octane requirement.Experimenting with different octane fuels until peak/performance/mileage is achieved is one way as well as cleaning the combustion chambers to remove deposits.
My wifes Toyota solara V6 runs ok on 87 but runs better and gets more mpg on premium as does my caddy N*.On the other hand my expedition gets 13.5 mpg and runs the same regardless what i use.
My wifes Toyota solara V6 runs ok on 87 but runs better and gets more mpg on premium as does my caddy N*.On the other hand my expedition gets 13.5 mpg and runs the same regardless what i use.
I will be difficult to figure out any of this because in most engines you have a computer chasing you and making changes. We've had carboned up engines (viewed with a fiber-optic device) that are knocking just a little, get lower mileage after getting cleaned out (also confirmed with the little device) and not knocking any more. Lots of theory here, too. Maybe it lowered the compression ratio just that little bit and the engine because less efficient. I do have one comment about gasoline additives. We have a small fleet of cars that always refuel from a tank we control. We add extra Chevron additive and the cars are likely to get the same dose all the time. These cars run better and have less fuel related problems than the ones in the same fleet that fuel whereever the driver is when he needs gas and almost always forgets to add the addtitive supplied in small bottles. Not science I know but interesting all the same.
As I stated above, I experience better MPG with High Test and the price difference only allows me to break even, so thats fine with me. One thing that I do not notice is better performance. The vehicle runs fine on any gas from what I can tell.
Octane is independent of the energy content of gasoline. The octane rating only has to with the resistance to detonation and nothing else.
Gasoline is a hodgepodge of different hydrocarbons. There is no standard formulation for the mixture you put in your car. Gasoline has to meet volatility requirements and octane requirements and after that about anything goes. Every morning the chemist has a list of what distillates he has on hand to work with and he mixes them up and tweeks the mix (for max output at highest margin) until the two requirements are met and sends it out the pipeline or to the rack. You can very well have two tanks of the same brand and grade with different energy contents. Variability, variability.
Gasoline is a hodgepodge of different hydrocarbons. There is no standard formulation for the mixture you put in your car. Gasoline has to meet volatility requirements and octane requirements and after that about anything goes. Every morning the chemist has a list of what distillates he has on hand to work with and he mixes them up and tweeks the mix (for max output at highest margin) until the two requirements are met and sends it out the pipeline or to the rack. You can very well have two tanks of the same brand and grade with different energy contents. Variability, variability.
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