When I used to work at a fuel station, when we ordered midgrade they would ship 1,000 gallons of 87 octane, and 200 gallons of 93 octane, then dump both in our midgrade tank.

Some stations now have pumps that do that mix upon dispensing.

When experimenting with premium, you have to be aware that any differences seen could be down to a more effective detergent and cleaner additive that is taking out any deposits and build up from the time of regular only use.

Decades ago, back in the days of leaded gas, Sunoco stations used to have pumps which would allow a person to blend their own, from straight Regular through straight Premium at (as I recall) 10% increments. Here in Nebraska there are a very few stations with pumps that allow one to select various blends of gasoline and ethanol, but I am not sure of the increments. I'd guess perhaps E10, E25, E40, E60, and E85.

It wasn't too long ago, a brand, I think Shell, had a fourth octane selection on its pumps between mid and premium. Considering the costs involved with maintaining and permitting the underground tanks, they were likely blender pumps. Lack of sales eventually lead to the end of that fourth choice.

The ethanol blender pumps have only recently started to be deployed. For E85, I'd still have to go into Philly, and possibly a station in NJ.

Jay's comment on the 2:10 ratio of premium to regular for midgrade octane raises a question concerning why the midgrade price tends to be at the midpoint between regular and premium. Is the reason purely because of marketing?

The Mobil stations here have a 88 octane. They call it special. It still has ethanol. I call it; not for me.
The midgrade prices I've seen are all over the place. Can get it cheaper than regular. I don't know what to think of it. It's all still with ethanol. Not for me.
The difference I've experienced with E0, makes me think maybe they're cheating with the E10. Might be more than 10%? Everybody loves to cheat here. What I read from others on the difference. I'm doing too good. Makes me think they're cheating.
I'm liking my performance with adding premium. Also noticing my computer on mileage is stronger. I'll have to wait to see actual mileage gain. The price may be worth just the performance and additives for cleaner injectors etc. I'll be experimenting with percentages of premium for sure.

I would say probably yes.

This weekend. I drove around town some. This is as much of city driving as I can get here. It isn't like in LA. Fighting traffic, etc. I can coast to stops. Coast down hills, etc. I do want to say...
With this E0 mix I'm running. The car was holding 40 mpg strong. Even up a little at one time. I don't know that the strictly regular E0 wouldn't do that? I do know the mixture is a better performer. I'm happy I'm holding 40 mpg in city.

I am noticing just how much driving habits effect MPG. I have had much on my mind lately. Have been driving without paying a high amount of attention. I only got 36.6 mpg. Unhappy with this. Admit, last time I didn't pay attention. It was with ethanol and got only 30 something mpg. Also, this tank had 50/50 premium/regular. Not sure that is the greatest for me?
I'm now trying 3 gallons premium, with 8.5 gallons regular. Is working good it seems. I also admit, I'm putting more effort into MPG. Computer is showing well above 40mpg. Much higher than my best so far.
I'll soon be driving a different route to work. Shorter, lower speed limit. Better in the wind. Only two definite stops.

Finally got over 40 for daily driving! 41.8!
I admit. I did keep the speed down to 45. It gets better mileage in the wind.
I had three gallons of premium in this tank.
This fill up going forward... 2 gallons premium.
I'm experimenting. Specifics? Can look at my page. I post notes.
I do think I can do better. Soon will be taking a different route to work. Moving. So I'll see.
Went 460 miles, and exactly three weeks on this tank. Feels good.

I am thinking just a little premium is best? Am experimenting.

For now. I've pretty much settled on one gallon of premium with each fuel up. I cut this fuel up short. Simply because I was in Rapid. Didn't want to take a special trip there, later this week, just to fuel up. Put only 9 something gallons in this time.
Mileage still came pretty close to best. If I held off. Might have exceeded it. Didn't have to try hard either. This rural driving is good mileage.
Wanting to get those Pirelli's on this car. Better mileage.
This is getting outstanding. Never dreamed of working with mileage this high in this car.

I just filled my tank with Shell regular at $1.96 per gallon. Premium was an unbelievable $2.50 per. It usually isn't at that large of a disparity level, but it was this morning.

I only run RUG with 10% ethanol in my '15 Mazda 2.0L automatic. I've thought about using non-ethanol and/or premium, but the price differential is just too large to justify it. At a 42.6 miles-per-gallon running average, I'm getting better mileage than the EPA estimate, so I'm happy. I think I'm getting about as much as I can with the least-expensive fuel available, so I see no advantage in changing what I'm doing now.

Fuelly says my lifetime fuel cost per mile with this car is at 4.5 cents after 18,000 miles, so that's good enough for me.

Just received my fuel credit card bill. Is so nice to have only one fill up on it.
Tank I'm on is going over three weeks. Could easily make four.
I is one happy camper.

I'm not sure whats going on with the diesel I put in mine last fill up, but it feels higher octane than usual, there's a noticeably louder noise from the engine and it feels more responsive, picks up speed quicker with less input. It's also indicating 68.2 MPG so far, with 450 miles travelled, I've got just over half a tank left.

Must be a good batch, I used the same station I always use.

I always thought that octane is only used in gas/petrol while "Cetane number" is the standard for Diesel fuel. Is it different in the U.K.??

Don't worry be Happy LOL

Last fill up was at $1.449 a litre X 3.78 (app) = $5.48 for a U.S. gallon Cdn or $7.30 when converted to U.S. Dollar. 94 octane non ethanol

Regular fuel was $1.29 or $6.50 per U.S. gallon in U.S. funds 87 octane up to 10% ethanol

Oh it was at a Chevron

Yea you could be right, I'm no expert on fuel to be fair, but this tank feels like it has the same effect as it did on my previous petrol car on performance/economy when using higher octane fuel.

The first time i used Shell V power was diesel in my i20 - and it delivered my worst ever, and only sub 50 mpg tank for that car! Kept me off the Shell forecourt for years. Thought i should test the petrol though, and got a decent 69.9 mpg for the Prius.
Due to having my first service, i was running late for a theme park (if i'm on a day out, i like to be there as it opens, not at midday!), so i booted it down the motorway at 70-80 mph. The drive was stressful, as very few people drive on the left unless overtaking, most sit in the middle and outside lanes at an unsafe distance behind each other.
Overtaking, you had to push in - middle lane hogs too lazy to even move to the empty outside lane to let you out. Over 100 miles and a pitiful 54 mpg (indicated). We managed to fit all the rides in though.
Driving back at 56 mph in the slow lane, adaptive cruise control on, was a treat. No hassle, nothing to overtake, listening to music and 88 mpg (indicated). Late home, but a much more pleasant experience.
At the dealers we sat in all the Toyotas and some of the Kias.
Only thing i was a bit jealous of was a full glass roof in a Yaris, would have loved that option. No other cabin really stood out as much as mine (must be all that unpopular white!) - and no heads up display in any of them.
Suprised by the Kia Optima plug in hybrid, a big handsome saloon. Nice green eco trim details. At £33,000 a bit more, but with 27 miles (claimed) electric range per charge, economical enough to recoup the extra?
They said could be charged from a standard socket - though bet my boss still wouldn't let me dangle a wire out the window...!
After a poor showing from my Hyundai, i am afraid i may be put off Kia too, despite their popularity.

There are a ton of plug ins hitting the market now, the Mitsubishi Outlander is the UK'S best selling plug in, may even outsell the Prius as a hybrid. But I feel plug ins are a bit flawed, the ev range is usually about 30% less than quoted, so a 30 mile range is usually about 18/19, and unless you charge the car at home, then at work twice a day, then the milage will be poor. On long journeys where you might only have 1 charge, you're just driving a big heavy petrol car, so expect poor MPG. I read a review of the Optima the other day, rated at 176 MPG, they managed 28 MPG...

Automotive class taught me that if Diesel had an octane number. It would be very high. Just like Jet fuel would be very high octane also.

I can only rationalize that what was experienced with 'better' performance with a tank of diesel is that a small amount of gasoline got into the tank. I mean the tank of the diesel station. Try gasoline in a diesel? You'll blow the engine apart.

Diesel engines are stronger, Fifth gear tested the "wrong fuel" scenario a few years ago, the petrol car with diesel didn't drive very far, but the diesel car with petrol in it drove ok, and kept going and going, and then they drained it, refilled it with diesel and it still kept going. They were pretty old cars though, modern engines are far more sensitive.

Gasoline (petrol) is compounded to resist ignition under conditions of high temperature and pressure such as those at the end of the compression stroke. It is supposed to ignite only when the spark ignites it, and is then supposed to burn smoothly.

Diesel and jet fuels are compounded to ignite easily under high temperature and pressure conditions. This works because the fuel is not present in the engine while the air is being compressed.

Every year a few piston aircraft are lost from misfuelling. The pilot orders fuel. The fuel truck driver sees some variation of "Turbo" on the airplane and thinks it needs turbine (jet) fuel. He fills the tanks with jet fuel. The pilot checks but doesn't notice the error. Engine start is normal because the fuel lines are still filled with gasoline. Engine run-up is normal even if the mixture of gasoline and jet fuel has reached the engine, because the gasoline will vaporize normally and because the pressures in run-up are relatively low. The takeoff seems normal, even though the low octane rating of the jet fuel is causing severe detonation in the engine. The pilot doesn't hear the detonation because of other noise, such as propeller noise. About the time the airplane reaches 500 feet above ground one or more pistons fail from the detonation, the engine loses power, and the pilot gets to try to make an unplanned landing.

Octane rating is a measure of how well a fuel resists igniting from heat and pressure.

Cetane is the measure of how well it ignites from a heat and pressure. A higher value could give better performance and efficiency by burning more completely than a lower cetane fuel.

In the owner's manual of my old 1986 VW Golf diesel, it said that in extreme cold temperatures you could mix a small amount of gasoline in with the diesel to prevent gelling. Unfortunately, I don't recall how much they specified and I never tried it as our diesel is blended for the severe cold here.

Decades ago Mercedes recommended mixing up to 25% gasoline with diesel fuel in really cold weather to reduce fuel gelling problems. They no longer make this recommendation. I believe it is because if the weather warms up the diesel fuel system is not designed to control the gasoline vapors, and there is the risk of fire.