Premium unleaded or regular unleaded

Regular. And regular is recommended.

Tom

 

you need nothing more than good ol' regular 87.

 

And Prius mileage will decrease with Premium gas, so don't buy it.

 

Yes. What others have written is corresct. It even says so in the manual (and, when paying $32K for the car, I would think that people would read the manual cover to cover but maybe that's just me. ).

 

Just emphasizing this point. With most cars, premium is just a waste of money, but doesn't do any good OR bad. But with the design of the ICE in the Plug-in, the characteristics of Premium likely lead to LOWER gas efficiency. So with premium, you will pay more money to get less mileage.

 

Drive what the owners manual says to use. Engines are built with an Octane level in mind based on how hot the engine runs.

If the manual says premium, use premium.

PHEV says to use 87.

 

Why does the Chevy Volty use premimum gasoline?

Seems counter productive to tout the greatness of the
Volt than require the owner to only fuel with premimum
gasoline.

 

The engine they chose requires it. GM did all they could to offer a car that no one would buy. Sadly for them, folks bought some anyway. I think the "Green Stickers" in California may be a real "Springtime for Hitler" disaster for GM.
The Producers (1968 film) - Wikipedia, the free encyclopedia

 

Actually the Volt uses Premium because the gasoline can be in the tank for a very long time, and premium breaks down slower than standard gasoline. Many Volt owners still have their dealer supplied full tank up to a year later, as they have a 35-50 mile EV range, and the engine will not start until that range is exhausted (unlike the PiP)

 

So, if the owner of a Volt is taking a long trip and will
be using the gas motor say for a 1,000 mile trip it
would be safe than to use regular grade gas as
the gasoline motor would be operating instead
of resting in the tank for weeks?

Would using regular grade gasoline void the Volt's warranty?

 

If people are not using the extended range capability a lot, the premium fuel does last a little longer,†- Volt vehicle line director Tony Posawatz
It is not a huge endorsement, but apparently this excuse IS official.

 

But as has been pointed out, a gasoline engine is designed for a particular octane fuel, and the one in the Volt has been designed for premium. They may have chosen premium due to its longevity, but having done so, that is what the engine requires. I don't know specifically about the Volt engine, but using regular (87 octane) in high performance engines designed for premium will misfire like mad and ultimately damage the engine.

 

Are you sure Premium reduces fuel economy in the Prius? Considering in many parts of the World, Premium is the lowest octane unleaded available. My understanding was that most Japanese and European cars are designed for Premium for that reason and then adjusted for the US market lower octane Regular unleaded requirements.

I use Premium (95RON 91AKI) and still get fabulous mpg's when I try.

[ame=http://en.wikipedia.org/wiki/Octane_rating]Octane rating - Wikipedia, the free encyclopedia[/ame]

 

I think you need to stick with premium on the Volt, that's what GM specifies, I guess a Volt owner would have to answer the warranty question.

 

This is how it was explained to me when I talked to an Engineer about the Dodge Viper and octane.

The higher the octane, the higher the combustion temperature, it burns at a higher temp.

So lets make up numbers here for demonstration purposes.

87 ignites at 200 degrees.
91 ignites at 240 degrees.

If you put 91 in an engine that operates at 200 degrees, it will not ignite correctly.

Same if you put 87 in a 240 degree engine, it will ignite too soon.

Ask your dealer, read the owners manual, ask google. Use the octane that the manual says you should use, nothing less and nothing more.

 

^
The ignition temperature explanation isn't too bad for an oversimplification, except that it needs a little more detail. Gasoline engines don't ignite the fuel/air mixture from cylinder temperature or compression, but from spark. Any normal automotive gasoline will ignite from a properly working spark ignition system, regardless of octane. The problem is with pre-ignition, or knocking.

When you squeeze a regular octane gasoline/air charge in a high compression engine, the mixture reaches it's ignition point before spark is applied, which is too soon in the compression stroke. The detonating mixture works against the rising piston, producing knock.

The other way around isn't so bad. The higher octane fuel mixture will spark ignite even in a low compression engine, so it still works okay. It's a waste of money, though, since the low compression engine doesn't need the extra anti-knock ingredients.

Depending on how the octane is boosted, some of the additives have less energy density than gasoline. This will cause a slight reduction of mileage. There are other effects as well, but they are more subtle.

Tom

 

The Volt has sensors and it will retard the spark to run okay. It does drop MPG.. I get 42-48 MPG_CS on premium but only got 35-40 when the car was accidentally filled with regular (it was also winter). The cost differential is made up by the difference in MPG.. so I'm not going do regular again.

 

Think 89 octane is ok, or should I just go with 87?