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RX350MTL

Do I Really Need To Put Premium Gas ?

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The specifications for the 2010 RX350 for the U.S. market have the following footnote:

[3]Ratings achieved using the required premium unleaded gasoline with an octane rating of 91 or higher. If premium fuel is not used, performance will decrease.

It was recently announced that the only change on the 2011 ES350 is that it is "re-rated" to use regular fuel at a small loss in power and torque. Note that the word "re-designed" was not used -- only the word "re-rated". Doesn't your RX use the same engine as the ES of the same year?

Sounds pretty much like our old 98 Camry V6 -- its owners manual says regular fuel is acceptable but that there is a slight performance increase if premium fuel is used.

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The specifications for the 2010 RX350 for the U.S. market have the following footnote:

[3]Ratings achieved using the required premium unleaded gasoline with an octane rating of 91 or higher. If premium fuel is not used, performance will decrease.

It was recently announced that the only change on the 2011 ES350 is that it is "re-rated" to use regular fuel at a small loss in power and torque. Note that the word "re-designed" was not used -- only the word "re-rated". Doesn't your RX use the same engine as the ES of the same year?

Sounds pretty much like our old 98 Camry V6 -- its owners manual says regular fuel is acceptable but that there is a slight performance increase if premium fuel is used.

All I know is that the owner's manual and the sticker inside the fuel filler door of my 08 RX 350 both say 'premium unleaded fuel only'..

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Not Another is it ok to use regular... :chairshot:

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I tell everyone who asks this the same thing, it costs somewhere around $2.80 more per tank to use premium. Why risk damage or performance loss over less than $3 per fill-up?

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I tell everyone who asks this the same thing, it costs somewhere around $2.80 more per tank to use premium. Why risk damage or performance loss over less than $3 per fill-up?

$3 is not a lot of money. I told my wife the same thing. Go fill up at Sams Club or Costco and pay 20 cents less for the premium.

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Right, if you are member of Costco or Sam, you already save $0.20 per gallon or $3/fill up. I think you want to have better performance than save $3 and may have trouble down the road. I have LS400 1993 and still use premium gas. It will run smoother with premium than regular.

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My RX 400h originally required premium but it was changed and when I inquired the service advisor said I could use regular. If it acted up use 2 tanks of premium. When I switched to the new 350 I asked him again and this time he said it was important to use the premium and that it would be smoother and get better mpg. Even though it is about 35 cents more per gallon I have continued with the premium.

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Here in the Lexus Manual.......

Take a look at page 398-399.

"If premium gasoline is not available & If 91 rating gasoline cannot be obtained, you may use unleaded gasoline with an octane rating as low as 87 (Research Octane Number 91).

https://secure.drivers.lexus.com/lexusdrivers/info/my-lexus/resources/download-owners-manual.do?docURI=http://tis.tmsnet.toyota.com/t3Portal/resources/jsp/siviewer/index.jsp?dir=om/OM48699U&href=xhtml/OM48699U_OM0034.html&locale=en

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I've had an '07 RX since new and have virtually never used anything but regular fuel. Every once in a while I'll buy a tank of premium or mid-grade but never notice a difference in mileage or performance. And yes, I live near sea level.

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You should use the lowest rated gas that gives you good performance. Try a tank or two of regular

and keep track of mpg, performance, and any 'pinging' noise. Then try a couple of tanks of the next

higher rated gas. And on to the premium. You will probably get a minimal better gas mileage from

thge premium but you need to weigh that with the cost difference. Maybe you could use a mud-grade and

have the best of both worlds. The onboard computer will override and compensate for any problems that

you may have with the lower grade gas. Use the one that runs the best.

I have several cars that are supposed to use premium and I have used regular in them all consistently.

One has a few miles short of 100,000 miles on it and runs great. It also gets great mpg.

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You should use the lowest rated gas that gives you good performance. Try a tank or two of regular

and keep track of mpg, performance, and any 'pinging' noise. Then try a couple of tanks of the next

higher rated gas. And on to the premium. You will probably get a minimal better gas mileage from

thge premium but you need to weigh that with the cost difference. Maybe you could use a mud-grade and

have the best of both worlds. The onboard computer will override and compensate for any problems that

you may have with the lower grade gas. Use the one that runs the best.

I have several cars that are supposed to use premium and I have used regular in them all consistently.

One has a few miles short of 100,000 miles on it and runs great. It also gets great mpg.

I understand what you're saying, but then why does the manufacturer say that premium is required?

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It's the only way they could get advertised HP and Torque values.

I see, so if I am not all that concerned with a slight drop in performance, then there really is no reason not to use regular? Using regular will not cause any damage to the engine?

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I would not go against the manufacturer's recommendation, it's there for a reason - as someone posted, it may be fine in the short-term to use regular 87, but over time I believe it will degrade performance. I guess it depends on how long you plan to own the car. Considering I keep mine 8 years or longer on average, I sure don't plan to risk it. And as other posters have also said, the price differential amounts to a couple hundred dollars a year more, max...

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I would not go against the manufacturer's recommendation, it's there for a reason - as someone posted, it may be fine in the short-term to use regular 87, but over time I believe it will degrade performance. I guess it depends on how long you plan to own the car. Considering I keep mine 8 years or longer on average, I sure don't plan to risk it. And as other posters have also said, the price differential amounts to a couple hundred dollars a year more, max...

Agree 100%..

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And $200 a year over those 8 years you owe the car is $1600. If the better gas makes the car last longer or saves a repair bill then great. If all it does is make a slight performance enhance that most people will never notice, then u just blew $1600.

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You need premium gas if you wish better performance, in particular acceleration, from your engine. If you have a turbo, it makes sense to use Premium on a regular basis, although it will survive without it. An engine will not suffer damages because it is getting 87 octane instead of 91 or higher. And before onsidering Premium fuel, I would make sure you use synthetic oil instead of dino oil. Actually, hard acceleration is hard on an engine. So regular fuel might help your engine. My 2 cents.

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The higher the octane reading of gasoline the higher the resistance to pre-ignition knock. If the engine senses knock it will !Removed! the ignition timing which will cause slightly decreased efficiency of combustion. This leads to lower performance and lower mpg. Because of the computer, no damage to your engine will occur. If your performance or mpg decreases to a point that it is a concern simply go back to mid grade or premium fuel.

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The higher the octane reading of gasoline the higher the resistance to pre-ignition knock. If the engine senses knock it will !Removed! the ignition timing which will cause slightly decreased efficiency of combustion. This leads to lower performance and lower mpg. Because of the computer, no damage to your engine will occur. If your performance or mpg decreases to a point that it is a concern simply go back to mid grade or premium fuel.

All of the V6 engines in Toyota cars are rated for regular gas. They use the exact same engine as a Lexus and they all have a 10.8:1 compression ratio. So who knows why Lexus rates theirs for premium gas. If regular is good for a Toyota then it would be good for a Lexus. I don't buy this idea of I can feel it run better with premium gas.Put someone in Lexus with premium gas and then one with regular gas and then wouldn't be able to tell the differance.

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All modern cars have computers that monitor fuel grade and knock, and will !Removed! the spark slightly to eliminate ping (pre-ignition). Premium is no cleaner or better than regular. It does raise the octane, and the car will have more power. Not much, and you won't notice the difference. And why would you need that difference, anyway?

But not everyone will believe this. I didn't realize the Toyota engines are rated for regular. Interesting.

If you want professional opinions - the car talk guys recommend regular fuel. Just because they've slapped a fancy name on the fender doesn't make these cars anything special. I've never used premium in mine, and may keep a car ~10 years.

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