fuel grade

bilalmd - How does your 1.8-Liter 2ZR-FXE "Atkinson" powered, 2011 GEN III/3G run burning your EU 90 Octane (eq. US 85 Octane) motor fuel? If your Prius 2ZR-FXE ICE runs smoothly, without exhibiting pinging or other ill operating behavior, I would start fueling with EU 90 Octane (eq. US 85 Octane), forget trying to blend the EU 95 Octane (US 91) with EU 90 Octane (US 85) fuels to match and produce 91 Octane+ (eq. US 87+ Octane), and pocket the ~14% per liter savings.

 

I can't imagine how your car would know the difference.

 

What is the altitude where you are?

 

Your situation sounds like Japan where they may also have a similar gasoline octane choice.
Previously I have asked the question:
>>What fuel grade does the Japan Prius owners manual suggest for Japan octane market?
No answer thus far.

Meanwhile, one approach is to use the 90 R+0 due to the cheaper cost.
An alternate approach is to sometimes use high octane if your high octane has better detergent additives.
Yet another alternate is to always use high octane if you feel it gives better MPG...MPG depends on ethanol E10 content and other factors which is not cetain but depending on the details of your fuel composition.

 

Life is too short to spent time trying to mix gas like that.
I'd start out with the 90-octane and see if you get pinging or the car tosses a code at you.
While you're driving around, go by a Toyota dealership and look in their service bays.
If you don't see a bunch of Priuses stacked in line waiting for new motors, then I would guess that the local gas/petrol os OK because the whole point with Priuses is saving gas.
In the US, it is not at all uncommon for cars to use 90 (US85) at altitudes over 5,000'


If all of this intimidates you, just use 95 and don't worry about it.
Good Luck!

 

I would just use the 90 stuff, however, mixing the fuel does change the octane rating proportionally. In fact, Husky Oil here in Edmonton mixes it at the pump to attain the different "grades" they sell.

 

I'm sure you won't get pinging by using 90 octane instead of 91.

 

THIS.

 

Elevation affects the fuel-air ratio in carburetors, therefore it affects pre-ignition in carburetted engines, but it goes the other way. The higher the elevation, the richer the mixture, therefore the likelihood of pre-ignition is reduced.

Nowadays most cars don't use carburetors, therefore altitude doesn't directly affect the fuel mixture to the same extent. An air sensor measures the amount of air entering the engine, and the fuel is metered accordingly. In any case, using a higher octane fuel at higher elevations doesn't really make sense.

 

I'd be curious where in Europe you are as I understood that all cars in the EU or associated countries are designed to use 95 unleaded. Very few places still sell petrol lower than this, maybe a few old Eastern European countries.

Is the 91 RON actually unleaded or some dodgy leaded stuff? I imagine that as US and JDM cars can use 91 RON, that using that in your home market shouldn't cause a problem.

 

In the USA we also have lower octane at higher elevations...not quite sure what altitude...therefore the lower octane sounds fine in general.

In the US, we have "top tier" gasoline which means extra detergent additives are added to all octane grades at the major oil companies. I would have no idea how Jordan manages that so there could be some quality concerns. But at your altitude the low octane sounds fine.

 

The funny thing about this topic is the OP is grinding about a 1.5% or so difference in octane rating. Guess what, the -actual- fuel you can buy varies by a lot more than that from day to day.

Just try the lower octane fuel for a few tankfuls. If you hear pinging switch back. If not, you can stay with it. Modern engines will adapt to protect themselves and the only thing "bad" that will happen is poorer fuel economy, though generally lower octane rated fuel will give better economy as it contains more high energy fuel. Higher octane rating means the fuel is harder to ignite, not that it contains more energy.

 

David - I actually agree with you that that energy content (and MPG) can vary. But why are you saying lower octane gives better fuel economy? Most generally, the higher octane fuel may also tend to have a little more energy too. I agree its possible to have lower energy premium (eg; if ethanol is used to boost the octane) but most generally if we are comparing apples to apples (same ethanol content) then the Premium will tend to have more energy content and more octane.

 

A higher octane-rating (not necessarily octane content) is determined by the presence of the branched-chain isomers (such as isooctane), which resist engine knocking, by having a slower flame-speed than other isomers. I had referred to this before as "slower-burning" which is essentially correct.
Gasoline Octane Rating - Engine & fuel engineering - Eng-Tips
Octane - Wikipedia, the free encyclopedia

The anti-knock qualities of higher octane fuels have nothing to do with energy content, additives or flash-point. It's entirely up to the fuel company whether they want to adjust the energy content, detergent-content or any other additive-content to their "premium" grade fuel, but there's nothing in the name "premium" itself that guarantees anything special about it, compared to "regular" except for it's anti-knock properties.

Pump Fiction - Marketplace - CBC News

 

As a general statement, not true.
It depends on HOW the higher octane number is achieved and how the engine is designed.

And for Mr. Tracy, the inverse is not true either.....in general because there are too many variables.

And for our resident expert on everything.........octane rating is a measure of the fuel's resistance to pre-ignition due to the heat of compression. That's it. I commend you for doing some research but your conclusions are a bit jumbled.

I know it is confusing to use the same word to mean 3 different things: there is a compound called ocatane; there is an octane number and then there is the octane "rating" of automotive gasoline.......ONLY the third one is usually discussed and bringing the other two into the conversation just confuses things unnecessarily.

Once ignited by the spark, it does not necessarily burn slower or more evenly.
If it does, the chemistry that causes that is not measured as basic octane rating.

 

I posted that because I'm not a petroleum engineer or a PHD in organic chemistry. I asked a Husky oil engineer. To quote him poorly, "we get our high octane fuel mostly by increasing the amount of alcohol in the low octane fuel." Alcohol has less energy than the many different distillates that compose "gasoline". So most of the time low octane rated fuel, at least from Husky, contains more available energy than high octane rated fuel. Other fuel companies may use different methods, and even Husky may have changed their methods. Or to put it another way, YMMV! BUT, to get higher octane from "poor stock", which is what we have now, you have to put in more additives. Most additives to increase octane rating contain less available energy that what's in the base fuel. So I stand by my original statement, and do note I did post "most of the time". Again, YMMV!

 

OK well Husky Husky ....I guess that's a Canada company so you are talking about Canada situation...these days in the USA most all grades have 10% ethanol max'ed out, so it would not be an option to increase octane by adding more ethanol (which is high octane but lower energy). But I am under the impression you have some Premium in Canada that is E0 so that would go against what the Husky guy was saying.