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Is it REALLY necessary for me to use the highest grade fuel in my 2005 Toyota Sienna?? I’ve had so much conflicting advice. AND, does the quality of gas change from company to company? If so, who sells the best quality for the best price? Thanks everyone!

Who does the best:

Most gas in your area will come from the same place- and then go to individual refineries where each company will add their unique blend of additives and cleaners. Some are better, some are not.

As far as the highest grade- if that is what your Owners Manual recommends, then you should stick with it. Those are the peeps that built your car, so they know what the engine needs to perform most efficiently. If you drop octane levels, you could experience predetonation, and could cause yourself come big engine repairs.

My guess is that 87 octane (lowest octane) gasoline is fine for your Sienna. Check your owner’s manual. I have a 2011 Sienna. Ordinary 87 octane is specified by the owner’s manual. I buy gasoline wherever I get the best price. After 38,000 miles, I’ve had no problems. I really have found no difference in quality among brands.

Lauren…the answer is in your owner’s manual. If the manual states that premium fuel is “recommended” then you can use any fuel you want to but performance can be impacted. If the manual states that premium fuel is “required” then you have to use premium fuel.

If you are stranded out in the boonies then use whatever fuel is available but start filling up with premium when you get back to civilization. Some mechanics will say that your knock sensor can handle any fuel but that’s simply not the case. If you burn a hole through your piston they won’t shell out for the engine repair.

If you don’t want to use premium fuel in a vehicle that requires premium fuel then it’s time to sell and get one that uses regular fuel.

missileman wrote:
If the manual states that premium fuel is “recommended” then you can use any fuel you want to but performance can be impacted.

You forgot the other half of the story. Fuel economy can be reduced as well, partly or totally defeating the purpose of using the lower-octane gas.

We’ve always used regular 87 octane gas in my wife’s 06 Sienna with no issues. The Owner’s Manual “recommends” Premium gas, but does not require it. I’ve compared regular versus premium gas and found little difference in performance and mpg.

Here is the link to the discussion.

Our 2003 Toyota 4Runner V-6 manual states that 87 octane is o.k., but that a higher octane will give improved mileage and performance. My wife gets better mileage with the 4Runner than I do and lets me know it. Once on a trip, I accidentally put in 89 octane and hoped the mpg gallon indicator would read higher. It didn’t and at the 10 cents price difference per gallon, I just wasted $1.50.
When my son was a teenager, we had a 1990 Ford Aerostar that had a mp indicator. My son was the economy champ with that vehicle. It was so embarrassing to me that I wanted to ban him from driving the Aerostar.

In most areas of the country, oil companies have “exchange agreements” that allows them to swap product amongst themselves with no legal (anti-trust) consequences…Somewhere within 50 miles of where you live is a “Bulk Fuel Loading Terminal” where ALL the gas stations in your area get their gasoline from…Gasoline (regular and premium) is a bulk commodity traded on the N.Y. and Chicago exchanges. “Mid-Grade” gasoline is a marketing ploy, a 50-50 blend (you hope) of regular and premium. Since NO car manufacturer recommends using this grade (why should they?) it’s just a sweet kiss to the station owner when you push the mid-grade button on the pump…Today, the “Station Owner” is usually a major oil company regardless of the name on the sign…

Regular gasoline (87 octane) is recommended for your Sienna. Using higher octane will not improve anything about the way it runs.

lion9car…I consider “fuel economy” a part of performance. Thanks for the clarification though for others.

“Today, the “Station Owner” is usually a major oil company regardless of the name on the sign”

Half of the gas stations in Washington DC are owned by one guy, and he’s taken heat for his monopolistic practices:

First follow the recommendations found in your owner’s manual for the acceptable octane. Other than that don’t worry.

Per Page 376 of your owner’s manual

Select Octane Rating 87 (Research
Octane Number 91) or higher. For
improved vehicle performance, the use
of premium unleaded gasoline with an
Octane Rating of 91 (Research Octane
Number 96) or higher is recommended.
Use of unleaded gasoline with an octane
rating or research octane number lower
than stated above will cause persistent
heavy knocking. If it is severe, this will
lead to engine damage.”

Basically you can use 87 octane and nothing bad will happen. But if you want to get the advertised power and fuel economy you’ll have to use 91 octane or better. Some engines are more effected by octane than others. The early versions of the Nissan VQ V6 were a prime example of an engine that recommended 91 octane or better but could run on 87 octane, but lost about 20 HP and 3-4 MPG in doing so. It was very noticeable, and there are some engines where it doesn’t seem to make much difference at all.

@Caddyman , actually when Chrysler introduced the new “Hemi” 5.7L in 2003, 89 octane was the required fuel. You can see for yourself on page 379 of the 2004 Ram manual here

My turbo charged engine recommends high octane, but I can use low octane if need be. I have yet to(knowingly) use one drop of 87 octane in my car. Gotta pay to play

Ah yes, “Jobbers”…They own multiple retail outlets, usually have their own bulk plants (terminals, tank farms) and deliver fuel in their own trucks…The big refiners love them. They never did like the marketing side of the oil business…The big money gets made between the wellhead and the refinery, not the gasoline pump…