Higher octane for better mileage?
 

I'm wondering if anyone has tried higher octane fuel?
Any better mileage?

I'm also wondering because, at times, the mid grade is cheaper than the regular. No, this is not because one has ethanol and the other doesn't.

It's generally considered that higher octane fuels give better performance and mileage, but are usually more expensive. Sadly there's nowhere local I can get any, but I have tried a tank in the past and it performs better overall.

I think I'm gonna give the mid grade 89 octane a try.
I checked. There's more than one station selling the mid grade cheaper than what I'm paying for regular.
I also have to admit. Maybe it's because of the ethanol. I have sat with my car idling for a few minutes. Longer than I would like to save gas. It got to where it was idling with a little vibration. Not the super smooth I'm used to. I rationalize that as the engine trying to ping. But the computer stopping it. Rationalizing it's fighting pinging. ????
I am impressed at the compression ratio. It's 10:1. That's pretty high while burning regular. Computer must be doing a bunch.

I've considered Premium. Also the Premium is easy to find with no ethanol in it. Cost is considerably higher. Which causes me a big hesitation to try it. That is also why I posted this thread. Hoping for feedback from people who have tried.

In times past when I have tried higher octane gas I have found that the improvements in fuel economy are diminished by increased cost of high octane. I stay with regular, unless the manual calls for high octane.

Higher octane in itself will not gain you better mileage, unless the engine was designed to operate on high octane fuel. The larger variable is the ethanol content. Generally, to get the best mileage use the octane rating that is called for in your vehicle owner's manual.

Let me pose another thought/question here.
If the engine is designed for 87 octane, without ethanol.
Would 89 octane with ethanol be accepted by the engine like 87 without ethanol?

My owners manual states that the computer makes adjustments to stop pinging.

I just checked a station that doesn't have the best prices. But they're not bad. This station has Regular without ethanol.
89 octane mid grade.... $1.88 a gallon
87 octane Regular......... $2.38 a gallon (no ethanol)
93 octane Premium...... $2.58 a gallon (no ethanol)

That's quite a difference. Right now I have 87 Regular with ethanol in it.

As stated, higher octane doesn't help unless the engine is designed for it. There is a chance that the owner's manual may not be telling you what that octane actually is, but what the marketing department thinks is best to sell that particular car.

Take the 1.4L turbo in my Sonic. It is an European designed engine, and it can make use of higher octane fuels. It does get better fuel economy on mid grade and premium, along with more power produced, but it usually isn't enough of an improvement to cover the typical price difference in fuel here.

I don't know if the foreign Aveo is labeled for regular gas or not. I do know the rest of the first world's regular gas is higher octane than the USA's, and anything higher than regular on the window sticker hurts sales of everything that isn't a luxury performance car.

The best place to find out if that Corolla's engine can make use of higher octane would likely be a model specific forum.

Ethanol has less energy per volume than gasoline, so it will lower fuel economy. It does have a higher octane though, so some of that lost could be gained in a high octane engine.

Odd that that station has no ethanol in the regular and premium, but not the midgrade. I thought midgrade was mixed from the regular and premium at the pump.

Some stations have "blender" pumps, that mix it as it is dispensed. Other stations have a separate tank. When I worked for a fuel station our "midgrade" was 1,000 gallons of 87 octane + 200 gallons of 93 octane, and all dumped into the same tank.

For around here. The unusual part is the Regular with no ethanol.
Now the Premium. Many stations advertise no ethanol in the Premium. Why? Those who buy Premium. If there is ethanol in it. They throw their terrible two's fits and all.

I burned mid grade in my last car. The reason was, when gas prices were high. The mid grade was the cheapest, period. I did notice that car had to make adjustments going from regular to mid grade or back. Took it the better part of a tank to make those adjustments.

87 octane E10(10% ethanol) has ethanol that is 114 octane. To balance the 114 octane ethanol in E10, the gasoline molecules have to average 84 octane. To raise octane by 3 points, just buy 87 octane, E0, which has no ethanol AND ALL THE GASOLINE MOLECULES ARE 87 octane. In my last 5 low 87 octane, low compression ratio (9:1 to 11:1) gasoline engines, E10 mpg compared to E0, dropped 8%, 8%, 8%-7%, 7% & 5%.

Yeah, adding just 10% ethanol to E0, drops mpg that much. 114 octane ethanol needs high compression ratio (16:1) ethanol engines to extract ethanol energy. 87 octane, gasoline engines can't do that efficiently, but work efficiently with 87 octane E0.

Thank you.... interesting results.
I'm definitely gonna experiment with my car.

Where is here?
Depending on subsidies and location, the ethanol in the mid grade could be what made it cheaper than the straight gas of regular and premium.

With improving sensors and computers, the cars should be adjusting to fuel blends faster.

Here is the Black Hills of South Dakota.
I did find two stations with much better price on regular E0. ... 203 and 197.... lookin' good. ..

Undoubtedly, the ethanol is what makes the mid grade cheaper.
Those prices I posted. They are in comparison to mid grade with ethanol up to 1.87 now. Not far from that.

I remember talking to people who had vari fuel vehicles. They could use the majority ethanol in their vehicles. I think it's 85% ethanol? Called E85? They said that it was much cheaper. But the loss of mileage offset the cost. Also their vehicle didn't run nearly as good.

Take that to the addition of ethanol. There are different amounts. Have to be careful. Can be 5, 10, 15%? Depends on the station. Where I get mine, they don't openly show it. They just make a big deal out of being "top tier" gasoline. I need to find out. If just for interest sake.
Going through this. In the past I haven't really paid much attention. Am getting oriented here. Also, I'm sure, I'll end up with the regular E0. Am definitely going to fill that the next tank. Counting on gaining mileage.

Researching....
In Rapid... all the regular E0 is 85 octane.
Have noticed other towns in this state claiming regular E0 at 87 octane?

Is the elevation there high enough to warrant 85 octane? If so, it should be fine as long as you fill with 87 before heading for the low country.

E85 will result in lower fuel economy, but should increase power. At least one of the posters at a Sonic forum switched to E85 for the power. The 1.4L turbo is an alcohol sensor shy of being flex fuel. The E85 fuel maps are just locked up in the ECU.

If premium gas on a window sticker didn't cost any car sales, flex fuel engines could do better on E85 with a higher compression ratio to take advantage of ethanol's high octane.

The EPA, at the behest of ethanol producers, is trying to push the E10 many places have to E15. The car and oil companies have pushed back, but newer cars are being made E15 safe.

The law that brought upon the ethanol mandate was written with two assumptions in place. One was that E85 would have become more widely available for flex fuel cars. I had a Ranger for years before a nearby E85 station opened in out of the way Philly.

The other assumption was that gasoline demand would remain the same or grow. It has dropped with more fuel efficient cars being put on the road. With the mandate stating a set amount of gallons of ethanol to be mixed in the gasoline, less gas means a higher percentage of ethanol to meet that number.

E7 is all that is needed for replacing MBTE, but oxygenated fuel is really only needed for carbeurated engines. Considering the number of older cars on the roads, E15 is just too much.

We should have an open fuel law that also allows methanol to be used instead of ethanol. It can be made cheaply from natural gas, which in turn could be made from excess renewable electricity, water, and carbon dioxide.

We should also increase our regular octane, and switch from AKI to RON for it. It will reduce manufacturer costs since that is what most of the driving world uses, and allow the introduction of more efficient engines.

Our elevation in Rapid is 3200 feet. The prairie out from here is about the same. Takes a long time to reach low elevation from here. Sioux Falls, which is about the same distance as Denver, but different direction. It's 1470. Gillette Wy, to the west, is 4500. The highest elevation town in the Hills is 5300 feet.
Not sure what you mean on low elevation? Or is this high enough?

As far as I know. The only station selling the E85 here is the flying J truck stop.

Octane is a measure of the gasoline's resistance to knocking. Knocking occurs from too much heat, which is mostly created by the pressure of compression. Higher compression ratios means higher cylinder pressures, and the reason high CR engines need higher octane fuel for full performance and efficiency.

At high er elevations, the air is thinner. This means there is less of it per cylinder volume. So the pressure when compressed is lower than when the engine is at sea level. This means a naturally aspirated engine can can safely use an octane lower than the US regular standard of 87 octane.

The 85 octane at those elevations might return the same fuel economy as 87. If so, use it if it is cheaper. Taking a car filled with 85 to a low elevation risks knocking though. I don't know at which elevation 85 octane becomes too low. I do think the knock sensors and ECU will protect a modern engine if that elevation point is past. But that is a call for the car's actual owner.

I've always found that running No Ethanol fuel nets me 2-3mpg better than ethanol fuel. My 95 will pull an extra 2-3 mpg from 91 no eth over 87 eth fuel while feeling more powerful, but the extra $.30-60 a gallon isn't really worth it.
On a newer vehicle designed for ethanol fuel, you likely won't notice much difference.

I remember my auto shop teacher, told us about octane.
He illustrated it by;
Stood at an open door. He hit the door with his hand. It pushed open more.
He said that is low octane. It hits the piston to make it move.
He then put his hand to the door and pushed. He said that is high octane fuel. Less hitting the door to make it move.
Basically.....low octane explodes more....high octane burns more...

This is not an attempt to explain methanol with it's lack of efficiency in an engine.

I just filled up with regular, E0, 85 octane. There is a definite world of difference here. Now bear in mind that it still has the 10% ethanol from three gallons in there. This car is performing completely different now. No more thoughts of; well got to get used to the transmission, or the extended idle resulting a little rough...no more of that stuff. I stepped on the gas and it surprised me. I'm just nudging the pedal now. Lots more power.
This tank I filled up. I got my best with ethanol. Came to 38.1 mpg. That's with a 60 mile freeway trip. The computer barely came up on 40 mpg...stayed below on the graph.
Today with this tank. Drove to work. Yup, I worked today. That computer went up to 50 mpg for the tank. Came back down and is sitting right at 40 now. This is a whole different world than the E10 ethanol. I never saw 40 there.
I have no idea what kind of mileage my car is going to settle on? I'm overjoyed with this regular E0. This car is doing far beyond my expectations. Still got some to do to increase mileage.
My car seems to be overjoyed. Gave it the 'hard stuff'....the Saki.

A lad at work says one of the supermarket chains expensive brands of petrol (there are no more than two types of each petrol and diesel at UK pumps, one usually about 20% dearer) is 99 octane, best in our market, with the Shell top line being 98 octane. I am tempted to test the Tesco one next...filled up on another supermarket chains regular when I picked up the car, is it was a minute from the Toyota dealers.

A quick fact check on Google says that in fact both Tesco and Shells top line are 99, while our regular unleaded is 95, and other brands top line (super unleaded) is 97.
I have no experience with petrol, but I seem to recall with diesel, paying 20% more to get a 10% improvement in economy. The sales pitch for premium fuel was that it also cleaned and looked after your engine, so every few months you'd feel like giving the car a treat...

That was a typo. Just noticed. I meant: ethanol. Not methanol.

The higher octane ratings in the UK are interesting. Is it about the same in Europe? I remember being taught that kerosene is very high octane.
Interesting the two brands. Was leaving out BP, just an oversight?
We've had problems with Diesel here. When it gets cold. It will gell. Plug up the filters. Plug up fuel lines. Out number 2 diesel is supposed to be good to 20 below zero f. That's about the same as -20C. It wouldn't even come close. In single digits 'f' it was doing that. I think they were cheating. Now they claim better and we still don't trust them.
That on the diesel leads me to think that maybe they have been cheating on the ethanol. More than stated? The difference without ethanol is impressive to me.

The RON or Octane numbers are different between the US and Europe so are not directly comparable. The fuels are very different though, we have more additives and less sulphur in ours, hence why we only need to change our oil once every couple of years. We also use winter blend diesel as you guys do, to stop it gelling, and recently I looked at my figures and noticed about a 5-10% drop in economy using it. Can't help with your other questions sorry.

Interesting on the winter blend diesel. Ours is supposed to be better. Called Number 1. Remember what I stated on Number 2. They claim our Number 2 is now 15 ppm Sulfur. My truck gets it's oil changed at around 650 hours. Use hours on trucks because they also sit and work. That's pretty normal for trucks here. Works out to a couple, maybe three times a year.
On petrol. I do find it interesting. Toyota has me using Synthetic Oil. Change it at 10,000 miles. No filter change in between. It's very light oil. 0W-20 weight. I trust Toyota's engineers.
Besides... changing oil every 2500 miles is much more hassle.

I enjoy reading the comparisons and differences. Don't have to worry about me using it to create a conflict of sorts. There are too many people in this country who are a conflict looking for a place to happen. Gee.... I even talk on a gun forum where we talk politics. It is a special forum. They kick troublemakers out. We still disagree and kid each other. The moderators have a wise eye for the troublemakers.

It's refreshing to chat to someone open minded like you my friend. Just last year I questioned the obsessive oil changes in the US as at the time, I didn't understand why the same cars here would require such little oil. This one guy sent a barrage of abuse, insulted me and my car and basically said he wanted to run me over in his enormous truck. Still makes me smirk today!

I'm not sure about the big semi trucks here, I should imagine they go by hours too, although I read on a manufacturers truck website that they do 60,000 between oil changes. The biggest interval I've seen for a light passenger vehicle is probably about 30,000 miles, on average it's around 15,000 to 20,000 with the modern synthetics, but it does recommend sooner if you've been "racing" or driving in dusty environments. I try not to talk guns here, it's a sensitive issue in the states. I mentioned it once and got shut down, I guess we should stay on topic ;)

That sounds about normal for people in this country these days. Looking for anything to run off in a tangent and throw a fit. I call them: "Terrible Two's Fits". No actual communication on anything. Nothing constructive.
That's why I spend much time online talking. Just for some intelligent input and interaction.
Can't even talk guns on many gun forums. They're awful. Same reason as above. That one I mentioned is special. Can't see a reason to talk them here.
I do sincerely appreciate the info. Different practices and such. Again....I find it interesting. Just makes me want to find out more.

The rating on the pump in the US and Canada is the gasoline's AKI; an average of RON and MON. A few other places also use AKI, but most of the world reports RON, which is a higher value than MON, and thus higher than AKI. US regular has a RON of around 91 to 92.

We should switch to RON and increase the regular octane rating. RON is the more important number for when it comes to designing modern, fuel injected engines, this should reduce the R&D costs for new models. The higher octane will allow higher compression engines, which should be more thermally efficient.
https://en.wikipedia.org/wiki/Octane_rating

I think you are confusing kerosene's cetane number for octane. That is an inverse measurement of what octane measures. The higher the value, to more likely it will ignite when compressed, which is what you want for a diesel. Kerosene and diesel octane ratings are very low.

Motor oil change intervals have gotten longer for various reasons. The oil itself, and the additives, have gotten better. It is possible for a 'synthetic' oil on a store shelf in the US to have no actual synthetic, group IV oils in it, and just be well refined group III ones.

Then the engines and their manufacturer have gotten better. Tighter clearances in the parts means less fuel and other contaminates get into the oil. Plus, the fuel has gotten cleaner. Lower sulfur in the fuel means longer oil life. The US is planned to start moving to ultra low sulfur gasoline in the next year or so.

A fuelly noob pipes up here. I just sold a 2002 Maxima, 6 spd manual, that I bought new. I put 145,000 miles on it, and kept track of my mileage with an Excel spread sheet.

Just before I sold it, I decided to try an experiment. I ran 2500 miles on regular (87? 89?, whatever) octane (Nissan specifies premium.)

Now, the previous 2500 miles on premium, I wasn't quite as mindful about fuel economy, and it was a different season, but ...

I got 1.3 mpg better on regular.

On regular, I did get a very slight knock on a low rate acceleration that was quickly stopped by the ECM. Heavy acceleration had no knock at all.

So, IMO, use the cheapest fuel you can. Once in awhile, run a tank of a name brand premium through, not for the extra octane, but for the detergent mix that it has.

I'll ask my brother about the oil change interval on his rig. He drives a gasoline tanker, with a couple of million miles behind the wheel. I do think that part of the reason the large diesel rigs go so long between oil changes is that they have such a large capacity oil sump (or tank, if they use a 'dry' sump). IIRC, it is very often over 10 gallons of oil per change.

They probably go by hours, not miles, because there is such a huge variation. An OTR truck will rack up many more miles/hour than a short haul truck.

The different season alone can have a big impact on fuel economy. Amoung other things, warm weather reduces the warm up penalty. Summer blend gas also contains more energy than winter blend.

Then there is the possibility that the premium gas uses ethanol to raise the octane, which also lowers the energy content. On top of that, most cars calling for premium fuel are more performance orientated than for efficiency.

I was just thinking about how premium gas also tends to have better additives. A bottle of additive added to regular should provide the same benefit. it might even be cheaper if you use the dosage amount for your actual tank size.

Now that you wrote that, I'm thinking that my brother in law (the tanker driver) said just that. If your engine doesn't knock on regular, just use an additive to help clean out the injectors.

Gasoline is fungible. The tankers go to a depot, punch in a code, and the gasoline & additives specified by the code are pumped into the compartments of the tanker. Off they go to a Shell station, or Speedway, or BP, or whatever. BTW, BP is working on getting out of the retail business.

Mid grade is sometimes mixed at the depot, and put into a compartment of the tanker, sometimes it is mixed by the pump. I don't think that it's made at the station by pumping premium & regular into the midgrade tank, but I'm not positive.

Gasoline engines(supposedly modified for ethanol) only have parts that won't get eaten up by ethanol. As I've stated above:

114 octane ethanol needs high compression ratio (16:1) ethanol engines to extract ethanol energy efficiently. 87 octane, low compression ratio(9:1 to 11:1) gasoline engines can't extract ethanol energy efficiently, but works efficiently with 87 octane 100% gasoline.

I saw a wonderful explanation of higher octane benefits on a YouTube video (sorry, can't remember which specific one). Here's the summary:

• You might get more power (various cars, domestic and imported, were tested)
• You might get a little better fuel economy (various cars, domestic and imported, were tested)
• In none of the cars tested (various cars, domestic and imported), running higher octane fuel resulted in saving money.

The only way to know for sure is to run a series of tests in your car. The difficulty is in coming to an accurate and meaningful conclusion, because if you've ever graphed your fuel economy using the same fuel each time, you'll notice considerable differences due to a variety of variables. It'll be hard to eliminate all those variables and attribute the change in fuel economy to the type of fuel you burn, unless it results in a substantial and consistent change.

Best wishes with your experiments.

I just filled up mid grade, 89 octane, which appeared to give most of the benefits of premium. I only did so because the price gap with regular has been dropping. It was 14 cents more per gallon. That is on the high side of the benefit being worth the extra price per gallon.

10 cent more for mid and 25 cent more for premium is the price point at which the Sonic will have a chance of getting better cost per mile than regular.

Ran into a new idea today.
Guy says his wife's Toyota Truck does best with 1/2 Regular, 1/2 Premium. This is the small truck with a four cylinder.
Talking E0 fuel only.
Our E0 Regular is only 85 octane.
East River with lower elevation it's 87 octane.
He say's this is better than all premium.
I think I'll give this a try.

I run the cheapest regular I can find. Last tank 3.3 cents per mile.

Midgrade is just a mix of regular and premium; either in a separate tank when delivered, or at the pump when dispensed. 50:50 would be a little higher octane than midgrade, though.

On the subject of mixing fuels, E30 to E40 might have a higher efficiency per btu than straight gas. If E85 was available closer, I had hoped to experiment with it in the Ranger.

Oh yes. Am well on my way to 40mpg for daily driving and I don't know how much more?!
Just got 39.3mpg daily driving. This tank had regular 85 octane E0. Almost no ethanol left. Maybe .3%?
Last tank was 2 to 3% ethanol left in it. Got only 36.1mpg. Same driving.
I can claim that with no ethanol. Am getting 20% better mileage. !

I still haven't put the P7's on the car. That's a gain on maybe a couple mpg?
I still drive through fast food and idle. That' a waste of fuel.
Otherwise pretty good driving for mpg.

Now this time. I put in 50% premium E0. With 50% regular E0. I estimate with what was in the tank. Probably a octane of 87? Pure 50/50 should be 88.5. The little I drove it. Feels more solid and stable. More solid stable acceleration. I'll see how this works out.

I'm happy as can be! Definitely have 40+mpg in sight! Yes! That's just for daily driving. Don't have any idea how good highway mileage will be. I can go years without doing any of that. hehe