plee82

1500 miles on premium. Just had a trip from MA to NY/NJ. 26 MPG without cruise control plus a lot of traffic in NY/NJ. Not bad. Also, Sports mode is finally feeling different from Normal mode. Reminds me of my Acura acceleration.

csinsc

Per the Spec sheet Compression Ratio 11.8:1
Recommended Octane Rating 91 or more

DocRock

Like any particular person's MPG, a host of variables affect the wear and tear on an engine (and the accumulation of deposits on engine parts). Besides the actual octane rating, the quality of the fuel is also important. Is it possible that 87-octane Top Tier fuel might burn just as clean (or cleaner) than Brand X 91-octane fuel?

More important, perhaps, is how you drive your car. One would presume that a car used primarily for stop-and-go urban driving and/or for short trips will have a different expected engine repair history than a car used primarily for long, highway trips.

dibl

That's the max (Otto cycle) compression, at full speed. At low RPMs, it goes into Atkinson cycle, in which the intake valve is held open past BDC and into the first part of the compression stroke, thus sending part of the fuel/air mixture back into the intake manifold before the valve is closed. Thus a lower compression has to result, while in Atkinson cycle mode. I think that's how they keep it from knocking on 87 octane, along with clever manipulation of the spark timing.

cmmetcalf

759 pages wow! My manual for the 2020 Rx350 on page 454 states clearly: 87 (research Octane 91). As explained in my earlier posting virtually all pipeline quality gasoline (meaning virtually all gasoline sold in most of the US) Colonial pipeline (F grade specs dated March 2016 for regular gasoline blendstock for blending with 10% denatured fuel ethanol - Specification 3.5.1 specs show a minimum required Motor method (MON) Octane of 82.0 with nothing specified for ROM. 87 Octane is specified at the minimum for regular gasoline. That is R+M/2 (Research method + Motor method divided by 2) of 87 minimum. With a minimum motor octane of 82, in order to get R+M of 87 the minimum research octane number must be: 92 for the math to work. The Plantation pipeline specifies the same value (after blending with ethanol ) page 7 PPL (kindermorgan.com) Regular RBOB. These 2 pipelines move 20% of all fuel consumed in the US and most of the products in the S/E, Mid-Atlantic and N/E US. Colonial's capacity is 3,000,000 barrels of fuel per day between Texas and New York. At 42 gallons per barrel that equates to 126,000,000 gallons of fuel per day. Quite a haul? Plantation adds around 700,000 barrels per day of capacity--- so another 29.5 (approx) million gallons per day. Canada uses the same R+M/2 method also known as AKI (anti-knock index) so the specifications are virtually similar.

As a general statement, the use of an octane higher than recommended by the manufacturer doesn't usually relate in higher fuel economy or performance increase relative to the additional cost of the higher octane fuel. I have owned an RX300, a 330, a 400h, two pre-2010 RX350s, a 2016 RX and now a 2020 RX and typically average between 26-27 on the road at a spirited cruise setting. If premium fuel added 1.5 miles per gallon, that would be a 5.6% gain over an average of 26.5 mpg. In my state (SC) averages show that the average cost for 87 is about $2.857/gallon where the average cost for Premium is $3.547/gallon. The difference is about a whopping 24%. As Car and driver noted in their summary of their August 4, 2019 article on "Is Premium Gas Worth It? They said: "If you buy fuel with an octane rating above the manufacturer's requirement, you're likely to feel it in your wallet more than the seat of your pants." (Car and Driver, August 4, 2019 retrieved August 24, 2021 from the below url.
Is Premium Gas Worth It? We Test High Octane on 4 Popular Vehicles (caranddriver.com).

I might also add that the additive packages in both fuels are pretty much the same---the objective being to reduce valve stem and head deposits and carboned intakes that plagued earlier blends of 87 regular fuel.

In short, the science of a benefit/cost analysis doesn't support the use of premium (91 or 93 AKI fuel over 87 AKI fuel) in the latest RX350s. However, basic economics always tells us that is always the consumer's choice as to where they put their money in maximizing utility.

Best to everyone

Quantum501

Luckily you and I have the 2020 in the US in which the manual states:"You must only use unleaded gasoline. Select octane rating 87 or higher. Use of unleaded gasoline with an octane rating lower than 87 may result in engine knocking. Persistent knocking can lead to engine damage."

I just did a run to Maine from CT and back and got 27.3 mpg on 87.....not bad.

FLM99

I agree with what the last couple of posts say - with 2 caveats. In hot weather, if I am anticipating a long high-speed or hill climbing drive, I fill up with premium. And, I use only top-tier gasoline. The federal standard for the detergent level in gasoline is pitiful, and top tier fuels (recommended by many manufacturers) compensate for that. Top-tier fuels may cost a few cents more per gallon (Costco excepted), but avoiding future engine problems is worth it IMHO.

dibl

I would argue that the correct conclusion of this excellent analysis is "The economic result of a benefit/cost analysis doesn't support the use of premium (91 or 93 AKI fuel over 87 AKI fuel) in the latest RX350s."

In other words, if the goal is to run the car with the least fuel cost necessary, the answer is to buy 87 octane.

If, on the other hand, the goal is to obtain the optimal performance (as per Lexus published specifications) of the 2GR FKS engine, then fuel with an octane rating of 89-93 is required.

IMHO.

mrolds69

Excellent!!! I think we're finally in agreement. Lock the thread, lock the thread...lol

coolbrazz

I'm on other car forums and this debate goes on there also.
Sometimes it goes the other way as for using 87 when 92 or higher is suggested in your high performance v8 go figure that.

raylor4

We've been running regular 87 in our 2021 RX since purchase, Nov. 2020. The engine sounded like a 4 cylinder, until I put premium 92 recently. Now the engine purrs like a kitten, as it is supposed to. Power is about the same. I will ask the dealer why the huge difference in the sound of the engine when switching between regular and premium, We drive mostly city, running errands. Maybe the engine computer needs a little tweak.

bamalam

I've purchased fuel at alleged Top Tier stations since buying my RX in April 2020. I say alleged because only one station in all that time displayed the Top Tier logo. Moreover, most of the Top Tier stations in my area don't appear on the Top Tier station locator. I was curious whether I was really getting Top Tier fuel, so contacted toptiergas.com yesterday. Their response was quick, specific and reassuring. Following is my question <PII removed> and their email response:

Me: None of the supposed TopTier brands (Exxon, BP, Marathon) in my area display the TopTier logo. Your locator includes a few of the stations, but not most of them. Note that all the stations are part of various convenience store chains (OneStop for Exxon and Marathon, Little General for BP.) My understanding is that a station selling a given brand, like Exxon, must be TopTier and they are required to post the logo. How can a consumer be sure they are purchasing TopTier gas if the logo is not displayed? My area is zip code <central WV> and several surrounding ones.

Top Tier response: Dear Mr. <bamalam>, Thank you for contacting us and for your interest in TOP TIER™ Detergent Gasoline. We always appreciate feedback from consumers. In regard to the TOP TIER™ Station Finder, some stations may have been omitted because of some data discrepancies which we are working to resolve. Please be assured, all of the brands you mention (Exxon, BP, and Marathon) are enrolled in the TOP TIER™ Detergent Gasoline program as licensed TOP TIER™ suppliers. If a Fuel Retailer (brand) joins the TOP TIER™ Detergent Gasoline program, all of their retail outlets (and all octane grades) in the country must adhere to the TOP TIER™ standards. Therefore, all gasoline sold at retail outlets enrolled in the program meet the stringent TOP TIER™ Detergent Gasoline standards.

Just a bit of background, the requirement to display the logo was included after the program was introduced based on feedback from fuel retailers and consumers alike. They wanted a simple and easy way to identify locations supplying fuel that meets the TOP TIER™ Detergent Gasoline standard. Recognizing this, many stations did display the logo, however, not all did. We continue to monitor and are actively working with all TOP TIER™ retailers in meeting this requirement. E-mails such as yours are very helpful and help us continue to address the gaps in this area.

Please continue visiting the website, www.toptiergas.com/licensed-brands, for the most up to date list of Retailers and Brands enrolled in the TOP TIER™ program. All stations offering a brand listed on our website must supply gasoline meeting the TOP TIER™ performance standard and requirements in all octane grades at the station.

Thank you again for your input and for taking the time to contact us! Have a great day!

All in all, they told me exactly what I was hoping to hear. I'm in the midst of a several thousand mile comparison of 87 octane vs. 93 octane in my RX, and will report the results in this thread when complete. You know, because we wouldn't want this discussion to ever end.....

coolbrazz

Very informative had no idea there is a website specifically listing this information. I used only Amoco in my cars when available in the past since they pride themselves of their superior additives until BP acquired them. I then researched 3 of the top companies near me (Exxon, Shell, & BP) to see if they included these additives which what I read they still do. Now I use BP if possible, guess it's as close to Amoco fuel I can get, and so far never had a full-up of bad gas.
Appreciate taking the time to share the info bamalam.

cmmetcalf

Consumer utility is always computed in micro-economic theory as relation between the amount of goods consumed as to the amount of happiness or satisfaction the consumer gets from that consumption. The micro-economic theory says that "economic man" will always base their individual decisions of the basket of good and services purchased based on maximizing total utility.. Thus, in the mathematical sense, that point is reached when the sum of all the marginal utilities is greatest. As long as the consumption produces a positive marginal utility (the utility gained by buying one more unit of a good (marginal benefit) vs. the additional cost of acquiring that good, i.e., Marginal cost) the consumer will buy the good.

Since I teach it, I can state that this concept used in many micro-economic models and the concept that "economic man" always acts rationally is being challenged by the thought that human beings don't always act rationally and the reduction of economic behavior to the earlier models of consumer behavior is not strong enough to provide a full explanation of economic activity and markets.

In my discussion I was very careful about stating that it was a marginal cost vs. marginal benefit analysis,. That is simply: the marginal benefit to buy and use premium against the marginal benefit of gaining fuel mileage by that choice was not favorable toward the use of premium when the marginal cost of 87 produced better cost/benefit results.Or stated another way: "Why would you pay 25% more for a fuel that only generated a 5-6% increase in fuel economy.when regular (87 AKI) was what the manufacturer recommended for the auto and the automobile performs acceptably with that fuel grade in the tank?

To be sure I noted that the consumer satisfaction or "happiness" could certainly cause one to decide on premium vs. 87. If it makes you "happier" (greater marginal utility for premium than 87) to buy and use premium, then by all means do so---it isn't the best marginal benefit/cost scenario, but the expenditure is entirely up to the amount of "happiness" you get out of the transaction. Lexus strongly recommends Top Tier (registered trade mark) gasoline (2020 Lexus RX350 Owners Manual page 459) not premium. This certification indicates that the additive mix blended into the brand's gasoline meets the Top Tier specification for such gasoline grades. Virtually every major producer and reseller of gasoline in the US, Canada and Latin America (and Costco is included) is a Top Tier refiner/retailer. See TOP TIER™ Gasoline Brands (toptiergas.com).Licensed Brands.In July of 2016, AAA published a study conducted a study on quality gasoline vs other grades that showed the Top Tier brands were 19 times cleaner than non-Top Tiers brands.

AAA: Not All Gasoline Created Equal | AAA Newsroom

Of equal interest to me was the survey finding on consumers:

· Three quarters of U.S. drivers choose a gas station based on location (75%) or price (73%).

· Nearly 1/3 (29%) chose a gas station based on a rewards program.

· Only 12 percent of U.S. drivers choose a gas station based on whether the gasoline contains an enhanced detergent package.

· Nearly half (47%) do not regularly buy gasoline that contains an enhanced detergent additive.

· Men (44%) are more likely than women (26%) to buy a gasoline that contains an enhanced detergent package, as are baby boomers (41%) compared to millennials (32%).

The article stated: ““Americans are six times more likely to choose a gas station based on the price of gasoline rather than the quality of the fuel,” continued Nielsen. “Since TOP TIER gasoline is widely available and only an average of three cents more per gallon, AAA urges drivers to reconsider their priorities when selecting a gas station.”

In short from the perspective of what gasoline grade to use, it would appear that both Lexus manual recommendations and AAA's research results lean towards a conclusion that enhanced additive formulation is a better bet than "premium" as the engine runs much cleaner thereby reducing intake carbonizing as well as most drive-ability issues. No where in their manual for my car or in their on-line gasoline specifications do they recommend greater than 87 octane for the RXs until you get to model year 2011. For 2011 through 2006 they recommend premium and then go back to 87 for the RX330s and RX300s through 1999. Which fuel grade should I use for my Lexus vehicle? (custhelp.com)

This discussion is not intended to add fuel to the 87 vs premium issue. It is a simple presentation of facts that might be considered when choosing which fuel to burn in the wonderful RXs that we all own and operate.
It would likely serve no further advancement for this discussion and I certainly agree with one commentator that it could be closed until some new facts based on research come to light or Lexus changes its recommendations.

My father was general manager of several major oil company's refineries in his career and I spent one whole summer doing RON and MON tests using the rating engines for the ASTM standards (as well as spending 5 years in major oil marketing, distribution and product supply myself. This is a subject matter with which my family and I had some extensive experience--- so Top Tier 87 for my RX. You do what makes you happiest.

With respect for all and be safe....

DocRock

This is the key point. "Utility" is not easily quantified, though economists increasingly seek to do so. Human behavior varies greatly. For example, my son-in-law never buys a new car as he believes buying a (presumably) well-maintained late model used car ("Certified") is the "better buy" because (most) new cars depreciate a great deal in the first few years. I, on the other hand, always buy new. I like being the original owner as a used car was operated by someone else whose maintenance and driving style are not completely known to me.

And, to this point, my wife and I always use Top Tier fuel which I believe is a good insurance policy for extended engine life. Our local Costco consistently has the lowest gas prices in our area with the exception of that Arkansas warehouse club where the gas is not Top Tier.