My wife has a Mitsubishi Eclipse Spyder 3.8 2008. The book says her engine requires 93 octane. It says she can use 87 Octane for emergencies only and get back to 93 asap. What is your opinion? Can she use an octane booster? Is 91 good enough? That is all we can find close by. Should she use 91 with no ethanol? Would that be as good as 93 with ethanol? HELP
@neferati, Baloney. Don't believe everything you read on the internet. Look at the outfit that wrote this hit piece. Fuel Freedom Foundation, dedicated to eliminating fuel. No science here, only politics, as usual.
The book says
Here is what the book says. It doesn’t get much clearer than this.
Beauty. Thank you itwt.
Looks about right 🙂
Thank you for the clarification @doc , I had no idea about that aspect 🙂 I personally try to stay away from politics...
Regardless, I just found in the archives that for example BMW recommends that the operation of their vehicles (in this case, an M car) with 95 octanes (euro-rating), but the data collected about performance was done in 98 octanes (euro-rating), and even going as far saying that 91 octanes (euro-rating) is also fine.
It doesn't make sense to me. Why would they recommend something inferior, if the official benchmarks are then done with something superior to achieve the best possible results?
As you can see @MountainManJoe there are many benefits in using higher octane fuel.
I don't speak Spanish. If the manufacturer says an engine doesn't need high octane gasoline, then there is no benefit to using it, and you're just wasting money.
I would use the 91 octane.
I always use high octane petrol with additives, despite being the most expensive one.
Higher octane will cause a bigger explosion, reduce/avoid knocking if there's any, and the additives keep the fuel lines, spark plugs and cylinders clean within. It's also fully compatible with cars since the 80's/90's as far as I am aware.
Also, car brands do their performance testing with the best fuel possible, I remember a long time ago in the BMW European website publishing their benchmarks, and mentioning which kind of fuel they used at the footer (which was always the higher octane one).
I also believe premium fuel allows you to drive further, at the same speed/effort.
For instances, people with motorcycles feel a very significant increase in acceleration speed, when they switch to high octane premium fuel, because motorcycles are lighter and it's possible to actually notice such a difference.
About the ethanol part, I personally don't know.
the ONLY thing high octane gas does is reduce knocking on high compression engines. And if your manual doesn't say you need it then there is absolutely no benefit. Scotty has repeated this ad nauseum.
This article is interesting and complements my answer perfectly: https://www.fuelfreedom.org/what-is-octane/
I disagree MountainManJoe, I've read car gas cap inside suggesting lower octane, than the one used in their official technical data results for performance and fuel consumption. Something is off in this 😆 maybe they are just advising to the bare minimum required to function?
taken directly from the article you linked: "they won’t provide a benefit "