jfelbab

The engine in your Lexus was designed to use 91 or higher octane fuel. That is why they put that instruction in he manual. If it was really ok to use 87 octane they would have so stated. The possible damage that can occur can ruin your engine. If that damage can be traced back to the use of the wrong grade of fuel you may find yourself with no warranty. That damage may not show up immediately, it could take months to appear. Kind of like smoking.

I wonder, since you see no value in using premium fuel, do you feel the same about other items for your Lexus such as tires, oil, antifreeze, etc.? Do you cheap out on everything for your Lexus?

CDN_Lexus

A big point that has not been mentioned above is the fact that the higher the octane level in gasoline the cleaner the burn (less emissions). The RX350 was designed to run on 91 or higher octane level gasoline to achieve its status as a certified Ultra low-emission vehicle.(ULEV II).

Hopefully that is important everyone.

Kan-O-Z

.72 cents was hypothetical. It was an example to show that the savings you see at the pump isn't the whole story. For instance if you see a $3 savings at the pump, the true savings may just be pennies...not $3. If MPG varies by more than 1mpg (which could be very possible), you actually SAVE money using the more expensive gas!

To top it off, the .72 cents also buys you more than just a warm fuzzy. It buys you more power, more smoothness, more fuel efficiency, a cleaner engine, and finally peace of mind that your engine not being degraded or damaged in any way. That's a whole lot for .72

I agree with you that in some cars the higher gas is a waste of money (For instance the Lexus ES300). These cars don't require the use of 91. 87 is just fine.

Trust me that Lexus didnt just put 91 in their owners if they didn't need to. Now a days, it's a great selling point if a car can run on normal gas. Lexus would take advantage of this selling point if they could. Unfortunately the 350 engine was designed for 91...so you can take that any way you want to. I know how I will take it

Yes you're right, it may take a few tanks to notice a difference. The computer I assume adjusts gradually to changes (just as it adjusts for driving style). Also keep in mind that there are so many factors that effect fuel economy, it's really difficult to do an accurate test. You have to make sure you are driving in the same manner, you are driving the same roads the same amount, the outside temperature hasn't varied a lot, the same number of passengers are in the car, etc. Basically all of the possible conditions have to be as identical as possible. Hoefully we'll see at least 1 mpg difference, maybe more.

Kan-O-Z

CK6Speed

iTrader: (1)

I haven't seen $0.30 difference in my state myself, but I have heard of it in certain select places. $0.20 difference between 87 (Our lowest grand) to Premium 92 (Our highest grade) is very consistent though. According to all the studies Hawaii still has the highest average gas price. I think we finally dropped below $3.00 a gallon average. Premium just a fee weeks ago finally dropped to $2.97, but last week it already went back up to $3.02 and higher.

JorgeGVB

We are only talking about gas in this thread. I am all for the best tires, sythenic oil (which is way more expensive and more enviroment friendly), the best car wax, etc. I even like premium beer! Like I said before, this has nothing to do with being cheap, so why make this thread personal? We are just discussing gasoline.

The problem for most of you is you actually believe 91 octane is premium gas. The word "premium" is just a marketing term for a bit more octane. It only cost the oil companies a fraction of a cent more per gallon to make it, but it is much more profitable to sell. Heck, there are even people buying 91 octane when the manufactures don't even recommend it.

If it was so dangerous to run 87 vs. 91 gas don't you think they would make the nozzles different sizes at the pumps, so you could not put the "wrong" fuel in your car. For those of us that are old enough to remember, they did exactly that with leaded and unleaded gas many years ago.

Actually your RX owner's manual does say you can use 87 octane, 91 is recommended. Tests have been run before and there is no proof your engine "will be" damaged by using 87. Do you really think Lexus, Mercedes, or BMW engines are that fragile? Besides, plenty of people are using 87 instead of 91 anyway, have you ever heard of a single case of a damaged engine that was proven that it was caused by using the wrong octane? If what you are saying is true, would it not be a big problem?

I am running 93 octane right now just to see if there is any evidence of improvement. If there is a measurable performance boost or MPG gain, I would switch back to using a higher octane.

JorgeGVB

In recent years in my area, the normal price has been .10 cents more for each level from 87, 89 and 93 octane. However, I have seen some crazy spreads for the past 6 weeks. Some of the stations have been selling regular gas for $1.85 and premium for $2.19. This past week the spreads are starting to tighten again, regular is about $1.97 and premium is around $2.21.

BobsGX

Around here, the difference in price between regular and premium fuel can vary from 20 - 50 cents per gallon. For example, last week I was in Hudson, NY and regular was $2.31 a gallon while premium was $2.81 a gallon. This was at Mobil, Hess and Sunoco.

JorgeGVB

My guess for the large spreads is people are not buying premium as much since prices went up. The stations are selling a lot of regular gas, so they get a better price and pass it on. The premium gas is older stock and is still being sold at the old price. Over time the spreads will narrow again.

jfelbab

Here around Milwaukee today, it is 2.20, 2.30, and 2.40 for regular, plus and premium grades. (87, 89, and 91 octane) Citgo and BP are charging $0.20 a gallon more for premium. That is about $3.00 a fill-up.

BBHanks

Just returned from a 5000mile trip. Used premium gas every other fillup.(350miles)otherwise used regular..NO DIFFERENCE in gas mileage..No knocks or pings..ran 80+ across Texas really nice ride..Now have a question. I have some left over OEM oil filters from my old 04 es 330 .will these filters fit my rx350?

Kan-O-Z

Why every other fillup? I think the engine needs a few consecutive fillup to get tuned to the new grade of gas. Flipping back and forth every fillup may not produce best results. Just a thought...not a fact.

Kan-O-Z

Tammy

"Now have a question. I have some left over OEM oil filters from my old 04 es 330 .will these filters fit my rx350?"

Almost missed this

The filter used in the previous RX300/330 used a spin-on filter; Toyota P/N 90915-YZZD1

The new RX350 (AWD & FWD) uses a replaceable filter element; Toyota P/N 04152-YZZA1

CK6Speed

iTrader: (1)

I mentioned once before that everyone should figure out if there is a difference themselves with their own cars and driving styles. For you, if you noticed no difference at all I would suggest you just buy the non premium. For me, I used to get 22-24 MPG using 92 Premium, and the few times I tried 87 regular I got about 20 MPG. Since I now run larger diameter rims on my RX, I can definitely feel a difference in low speed acceleration as well. Honestly, the largest difference for me in terms of gas mileage has been when our state switched to E10 earlier this year. That alone reduced my MPG by about 2 MPG on the RX. I no longer can get about 20 MPG:

CK6Speed

iTrader: (1)

There is a little more to it than that. The manual does state that your car is equipped with knock sensors, so it is safe to use lower grade fuel, but at a potential of reduced performance. That doesn't mean it will always have a reduced performance level, but that under certain conditions, the knock sensors will do its job and reduce timing advance and that alone reduces power. The oldest trick on the book to get more power out of a NA motor was to advance timing. The oldest trick to prevent knock and engine damage on a forced induction motor was to reduce timing.

One thing we have to remember is that most modern cars with knock sensors, owners should never hear knock because the anti knock system is supposed to prevent that from occurring. If you ever hear knock in one of these cars you are well past what the anti knock system can do. 87 octane should not put you past this limit.

Another factor to consider is if the knock sensor has a failure and fails to detect knock causing the system to fail to dial out the advance timing? What will happen then? I personally have never had one of these sensors go bad so I think it would be extremely rare, but it could happen.

I have not seen engine damage on regular cars from using lower grade fuel, but I have heard of engine damage on modified cars that have such a high degree of timing advance, or forced induction. Surely this wont apply to the RX owners since I doubt much RX owners are modifying their engines, but too low octane has caused engine damage before(Not talking about RX).

For me, I never state it is okay, or flat out say it is not okay to use lower octane. I always try to provide as much information that I personally know (Not that I know a lot ) and let the owner make up their own mind based on that and whatever other information they may gather.

I think the bottom line for everyone is you need to make up your own mind. Not everyone is driving the same, nor in the same conditions. I'm running on 20" rims with over sized tires, lowered suspension, and a little added weight from extra A/V equipment in humid Hawaii weather. My vehicles performance level will be different from someone running in high altitude Colorado. When some owners see differences and others don't there are legitimate reasons for it. Do what you feel is best for your car an wallet.

JorgeGVB

That's interesting about E10 and reduced gas mileage. I have been using E10 also and was wondering why I have been getting such low MPGs too. In fact, now that I am using premium, my gas milage has went down even further.