Should I use premium gas? Explained like you're 5.

But not always... I'd be okay with trying it once since it only requires a $1.90 commitment. If I were able to see the results of Xray, that $1.90 would be worth it. But without ever trying, I may be losing out on more money that $2.00. Why is having too much information a bad thing?

 

Too much misinformation is a bad thing.
Premium does not (in general) have more energy than regular
Premium does not (in general) have more detergents than regular. (and if it does, they are in place of power producing gasoline)
Premium is not (in general) as fresh as the regular at any station. (Gasoline is a mixture, not a compound, over time it separates)
Premium will not (unless your car is designed for it) make more power than regular.
Premium will not (unless your car is designed for it) get better MPG.

So a quick read in your owners manual will reveal any need for premium. No need to waste money.

 

I wasn't giving misinformation. All of the above is true, except for the times that it isn't. But you guys are right. I'll read anything that is untrue and let all new people accept the misinformation as truth from now on. Hard rules are generally bad ideas in any situation. You guys are set on not trying it, great... don't try it. I did try it, didn't work for me. Worked great for Xray and he backed it up with evidence.

october update on mpg:

regular e10 cost $3.14
preimum e10 $3.34

miles with 92 octane e10 since feb.= 2554/39.42 gal gives 64.7 mpg
miles with 87 octane e10 since feb. = 2403/42.72 gal gives 56.25 mpg

tank in feb. 87 e10 gave 52.9 calculated at pump
tank in mar 91 e10 gave 59.6 calculated at pump (11% increase)
tank in april 87 e10 gave 57.1 calculated at pump (4% decrease)
tank in may 92 e10 gave 67.7 calculated at pump (15% increase
tank in june 87 e10 gave 57.81 calculated at pump(15% decrease) I forgot to log this when I filled up it is on fuelly.
tank in july 92 e10 gave 79.7 calculated at pump (huge increase) hypermile effort on my part not good for compairson.
tank in aug 87 e10 gave 57.1 calculated at pump (down a little from june)
tank in sept 92 e10 gave 56.84 calculated at pump( lots of hwy miles)
tank in oct 87 e10 gave 56.18 calculated at pump( 50% hwy miles)

this shows a 13% improvement in mpg with a current cost of .20 more the cost is about 7% more per gal. so if I am thinking correctly I am saving about 6% on my fuel bill by using 92 octane.

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Read more: Should I use premium gas? Explained like you're 5. | PriusChat
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Not sure why you guys all take offense at this. It takes 1 tank of gas to figure out that it will or won't work for you. Let them try it or let them not try it... but why is suggesting people try it so offensive to people?

 

I've been tempted to try a tank of chevron's highest octane, because it's the one grade that is guaranteed ethanol free. Still ill probably resist.

 

...because this is America?

or should I say: ...because this is the Internet?

 

Again, the recurring misinformation, is that there is any point to premium in a car not designed for it. Just like the other 25 threads about gasoline.

 

There isn't a point for most people. Correct. For the rare few, like Xray, there could be a point.

 

I would be happier with a 'blind' test, corrected for temperature, but if xray was conducting a rigorous test, yes.

 

interesting...
will try premium on next fill-up and see... :y

 

First of all, let me preface everything by saying I always use the recommended octane..which in The Prius is regular. OK....about once every 5000 miles, I run one tank of Premium....just for kicks. Don't know if it helps anything, don't think it hurts...it's just ritual for me. But 99% of the time? I run regular.

My experience however is that high octane fuel does NOT hurt my gas mileage. I get as good, sometimes better gas mileage with my premium tank as I do my regular. It may not be significantly higher or better gas mileage with premium, but it certainly isn't less fuel efficient or in any way noticeably "less powerful".

My rudimentary understanding of higher octane is that it ignites at a higher compression than lower octanes. Which is beneficial to engines designed to operate under those parameters. Some vehicles DEMAND premium. Thankfully...The Prius is NOT one of those engines.

This truth aside? I believe the Prius engine will adapt to higher octanes. The fuel DOES still ignite with every cycle of the Piston. It may take more compression within the cycle BUT...it's not like the gasoline, premium or high octane ISN'T igniting and being used.

I recommend using regular in The Prius. However I'm not convinced using Premium or a higher octane would result in poorer gas mileage. It will however result in higher fuel costs...and IMO unnecessarily.

 

...no not you MJ, you are not one of the chosen ones....those of us, like you and me, getting EPA reformulated gasoline, we do not have much chance of seeing any improvement with Premium. But if you get up to XRAYDOUG's place in Oregon, check out his Premium for us. I'd do it myself, but I am stuck here Virginia.

 

Higher octane, or the ability of the fuel mixture to resist igniting in places rather than a smooth wall of combustion, is determinied primarily by the compression ratio. In general engines with compression ratios greater than 9: 1 require higher octane fuel. High performance cars have higher compression ratios because more power is squeezed out of the compressed air/fuel when compressed greater. (thats why diesels are so much more efficient). Fuel is a mixture but doesn't separate easily so its not a problem but does distintegrate with time so gas stored needs a stabilizer.
In general, higher octane gas has more energy, hence mpg, but its not guaranteed. It depends on where the crude was refined came from and the reinery conditions. On track you might be best assured of top engine performance with high test but on the sreet its a waste of money. BTW, its tough to accurately measure the amount of gas consumred due to the uncertatainty of just where you refill to so you have to do the check over 10 tank refills each regular vs high test.
BTW diesels have good mpg but require heavy pistons etc so low rpm is required and since hp depends on rpm they usually have low rpm limits and thanks to heavy rotating parts accelerate slower too. As Mazda demonstrrates they have developed some techniques that allow highr CR's and still use regular (unless you get some low octane regular).
cheers
PS if you add a bottle of injector cleaner (non-alcohol preffered) to your tank once a month it will do way more good than filling with high test.

Gas has little octane c8H18 in it; octane rating is a comparison of fuels with pure octane. Pure octane is not very good gas. Most gas contain literally a hundred different ingredients and their quantity depends on where the crude came from and the refinery processing conditions. everal compounds like toluene have high octane ratings and high energy per gallon of the energy released when the gas is burned. And burning is correct, when gas expoldes it results in detonation or knocking because the energy release is sudden, not instantaneous. High test gas typically have more toluene and others like it than regular but again its not guaranteed. Buying gas is somewhat of a gamble.