I never check the MPGs but my '15 runs great with premium and mostly Shell 93.

 

Hi all,

As my signature says I own a 2011 RX350. Now I know there have been several posts regarding the grade of gas you're allowed to use in the RX350. I have come to the conclusion that I will switch from using premium gas to regular gas. Now I just have a question, since I have been filling premium gas since I got the car, will it hurt if start using regular gas now? The only reason I am asking is because the car is "used to" getting premium gas and just want to make sure no harm will be done.

Thanks.

 

It will not hurt the vehicle. You will lose a few horsepower as the computer will adjust the engine timing for the lower octane. Most folks cannot tell the difference.

 

Your car will not revolt against you. You will not know the difference, except for an extra .40/gal. in your pocket, and maybe .5 to 1 MPG less, which is an excellent upside for you.

We bought a used 2013 with 45K on it. We have never used premium in the 5k miles we have driven it. Last month, we did a trip from LV to Flagstaff, round trip of 570 miles. With cruise set on 75 & 80, we averaged 24.7 MPG, hand calculated, but supported by the trip calc of 24.8.

Based on the price diff between reg and prem, we would have to get 29MPG on prem. to make it cost effective.

 

One thing to keep in mind in this discussion is the potential for non-premium fuels to have higher deposition rates within the combustion chambers. That said, even all "premium" fuels are not equal as some will have better detergent and non-fouling capabilities than others. The point is that these combustion deposits don't just land in place in a short time frame, but can take their toll slowly over time. It's just another facet of the issue to consider.

 

Pete, that is certainly correct. I should have added that we only use Tier 1 fuels. Each grade of those "should have" the fewest contaminants, and optimum detergents, compared to others.

Is it your opinion that a Tier 1 Regular gas will, in the long run, damage the RX350 engine more than would be seen with the same vendor Premium fuel. I have heard that before, but never been able to understand why, considering the ECM adjusts the timing to the fuel octane so that there are no additional deposits or emissions. I would sure like to know if there is definitive evidence that indicates damage will occur earlier with Tier 1 Regular fuels.

Help me out if you can.

Jim

 

My two cents (perhaps 40 cents): I run my 2013 RX350 on 93 octane, usually Sonoco. (93 is only 2 cents more than 91 so why not) The question to ask is how the ECU knows the octane of the fuel it is using. It has no sensor for that. It adjust it by sensing detonation. Once it senses detonation it makes adjustments in a lot of things to stop it. The engine will experience more detonation on 87 octane than 91. Detonation is bad for an engine. I try to take the best care of my car even if it costs me 40 cents per gallon. The 2013-2015s are supposed to be able to run on 87. There has been a lot of discussion and controversy as to what Toyota did to make these engines different than the 2010-2013s, if anything. In the end will it really matter, who knows.

 

I appreciate your response, lawless, but it does not reflect reality. Knock/detonation does not occur, and then get corrected...it is corrected before it occurs. The ECU in any modern vehicle makes adjustments to operation in milliseconds, and can easily determine and satisfy a vehicles need well before it occurs. Every vehicle marketed in the U.S. must have the ability to run on "regular" fuel, whether it is best for it, or not. There is no detonation on a properly-operating engine, unless a fuel with lower than 87 octane is used, or the vehicle is pushed at it's performance limit for an extended period. Some people experience detonation, and find that one of the many sensors in their vehicle is not operating properly, or the engine is out of tune, etc.

Here is a quote from an expert pertaining to the use of regular fuel in a vehicle for which premium is recommended: "“Modern engines prevent the damage from happening before it starts,” said Patrick Kelly, a fuels analyst with the American Petroleum Institute. “It wouldn’t impact fuel economy. And it wouldn’t impact the emissions. What it would impact is the performance.”

There is a similar quote from a Senior Analyst at Porsche indicating that the vehicle will run fine on regular, "but, you will not experience all the performance available form the engine"

There is unlimited data online indicating that no harm is done to any engine by using regular fuel. I fully understand the rationale for using premium, and applaud your dedication to taking the best care of your car possible. That is why we have choices, and they are both reasonable. The OP was seeking information regarding any damage that may be done by using regular, and I believe I have answered that accurately.

These discussions are always beneficial to everyone.

 

ive been asking this for months now around various forums/reddit and have yet to receive an answer... Does the 93 Shell nitro vpower have more cleaning detergents/additives than regular 87 shell??
I like to use nitro thinking it will keep my internals cleaner, not for performance. But that could be me being a complete idiot! oh well

 

I agree with this..

My opinion on this topic is simple. Although you can run the RX on regular, since premium is recommended thats what I use.

 

Please forgive my long-winded addition to the very thoughtful discussion you folks have been having. In the several years I worked for a large privately held synthetic lubrication manufacturer and fuel additive formulator, the summation of what I learned has already been covered by others. I do see several issues, though, which are worth addressing.

1. Does the 87 "regular" fuel have lower levels of detergents, higher levels of contaminants, and/or reduced combustion efficiency/cleanliness as compared to the higher 91/93 octane fuels? In short, the answer is "yes". How much difference depends on the fuel manufacturer and which additive components and ratios they utilize for the different octane levels. All that stuff is highly proprietary and there are subtle differences between additive blenders throughout the US fuel market. I do not have enough current information to rank any of them any more, and have not had that info for over 5 years, so I will not even speculate on it.. All I can say is that there are differences, and some can be significant (between the "regular" and "top tier" fuels). I don;t mean to be cagey on this, but there is no simple answer to the relatively simple question.

2. How much difference is really taking place when substituting regular fuel for OEM-recommended premium fuel? That really depends on the manufacturer's engine design and combustion control strategy from that manufacturer. I know for a fact that some "high end' vehicle makes experience worse than desirable levels of carbon and petroleum byproduct depositions on the fuel side of the engine, and it can be equally problematic for sludge buildup on the oil side of the engine... either or both conditions being made worse by using grades of fuel/oil which are "below" the OEM manufacturer specification. The oil sludge problems are typically reduced most effectively by not only using OEM oil grade specifications, but also OEM specifications for drain frequencies. Regarding fuel, the "solution" to deposits are simpler in that the choices are limited to your choice of fuel and whether or not you choose to use effective aftermarket fuel additives WITH the fuel, along with proper proactive cleaning/maintenance efforts for the MAF and O2 sensors, intake air filters, and throttle bodies, where applicable. There is no magic or consistently effective road map for success outside of timely maintenance and the use of high quality manufacturer-recommended fluid specifications. Even then, there can be anomalies in deposition rates. Some vehicle manufacturers do a better job of designing around these issues, but it gets more difficult when you start chasing (pushing) performance envelopes for both MPG and HP. Do a search for carbon and oil sludge buildup problems, and over the years, you will find that most manufacturers have had to chase solutions to their own design problems (Nissan, Porsche, Audi, VW, Toyota, BMW...).

3. I'm with JT4. KISS the problems! I'll happily use OEM recommendations at a minimum, and will exceed them if reasonably possible. For me, that means full synthetic oils and top tier fuels, along with periodic (and short duration) use of aftermarket cleaning additives on both the oil and fuel side of my engines (either Marvel Mystery Oil or Kreen, depending on the age and mileage of the engine and its history of prior cleanings).

4. The phrases "does not effect MPG" and "only effects performance" can be misleading, and you should not take them to both be true at the same time, even though they were probably both happening simultaneously during the engineering tests. Let me explain... The first statement can certainly be true by itself when evaluated under controlled testing environments (same speeds, same acceleration rates, same road geometry, same engines with same miles, etc.). At the same time, you can certainly observe the reduced performance from lower grade fuels. However, what is a real world consumer driver really going to do when they feel reduced performance while driving with a lower grade fuel? What would you do? What would I do? The typical response is going to be a little faster and harder push on the "go pedal". The true result cannot help but be a reduced MPG and reduced performance!

NOTE: One more thing to keep in mind is that "low mileage" vehicles are generally operating under the harshest of conditions... higher ratio of start/stop cycles per 1,000 miles, higher incidence of inadequate time at operating temperatures, higher frequency of rev/slow cycles per 1,000 miles, etc. These conditions accelerate wear rates inside the engine. Consequently, since I only buy used vehicles, I have to remind myself all the time that "low mileage" vehicles are not necessarily the best purchase choice. Why do I say any of this? The implications of these truths should drive us to be aggressive with our attention to maintenance cycles if we are in the "low mileage" class of drivers. We need to be diligent.

 

It's common statistical analysis. The manufacturer performs many tests across a wide range of engine operating conditions and gathers a statistical baseline for nominal operating conditions and how measurements change as the engine approaches less ideal operating conditions while assessing how to mitigate these changes with engine control systems. This information is built into the control systems that ensure operating conditions stay nominal (within the limits of the control systems, obviously filling your tank with diesel will exceed the ability of the engine controls to mitigate any operating issues).

It's kind of like walking towards a brick wall. You don't need to actually walk into the wall before realizing corrective action is required, you can see it coming and take corrective action beforehand. With premium that wall is just a bit further away, but it still exists!

 

I never wrote the words "knock detection". Why did you feel a need to transfer my post for your reply, but change the wording? I did write the words, "knock/detonation" which is wholly different from "knock detection". I would usually just chalk this up to someone misreading something, but you specifically changed the words, then passed it off as if they were my words....

 

I can't answer that, and can't find an exact answer on the 'net. It does have just over 11% ethanol, which is how it gets the high octane rating. BTW, the actual research octane rating is 98!! That accounts for what I see as the high price of that gas.

 

Just found a couple of interesting reads (albeit rather short and non-technical) regarding the "value" of Top Tier gasoline fuels in the US.

http://www.consumerreports.org/car-m...h-extra-price/

http://newsroom.aaa.com/2016/07/aaa-...created-equal/


And below is a simplified article which does fair job of explaining octane, engine timing, and fuel choices. It does not, however, really address the separate issue of detergents in fuels which are often associated with higher octane choices, but that really depends on what the refinery and fuel distributor does (or does not) do in regards to injecting these additives prior to final delivery at the station.

https://www.carthrottle.com/post/eng...octane-petrol/