If the Camry V6, Sienna, Highlander V6 and probably Venza V6 run perfectly OK with reg gas, why would the RX need premium?
I own a Honda Pilot and a V6 Highlander. None of them ever tasted anything but regular and never had pinging/knocking or any other issues.
I will be picking up an RX this week and passing the Highlander to the kids.

 

technically, you dont need to put premium in it. the ecu will adjust for the lower octane and you will not get any knocking. However, premium fuel will give you the most efficient driving in both power and gas mileage

 

I remember reading on forums for other luxury brands like BMW, where dealers or mechanics have told owners that it is okay to fill the car up using regular or mid-grade gas for the most part, but to fill it to the tank w/ premium gas on every fourth of fifth fill-up. I no longer remember what the reasoning behind this was, although I know there was one given. But supposedly you get the same or similar results as you would filling up the tank with premium every time. Anyone hear any similar stories or rationales?

 

Same thing with rental cars, none of them drives like it supposes to. No power at all, and gas mileage sucks. Everyone is filling up with the cheapest gas they can find.

 

I know this subject comes up time after time but I fail to see the big deal with just running premium gas as the manual recommends. I don't see how someone can be talked into buying a $50K car and yet they resist buying premium fuel. Are car sales people that good??

 

First off there is no such thing as a "dumb question"! I agree with DNC, if you are going to purchase such a expensive vehicle treat it right and put in what Lexus recommends. If Lexus says use Premium then use it! Because they are not just saying it so they can make more money ;because obviously they don't make any money if you fill up with regular or premium, but they are just trying to help us out by telling us to use Premium.

The RX has a high compression engine if i remember correctly (someone please confirm this), so it needs as much octane that it can get.

Premium only cost's a few cents more than Regular. So let's just say it's another $2-3 a tank. But you get better fuel economy using Premium fuel, plus with the higher octane you'll get better performance. In the end the Premium will pay for itself, because of all those benefits.

 

It's Sat morning, and I have time to kill, so it's time for some math (and I may be wrong so feel free to correct). Around here mid grade is generally .10 more than regular and premium is .10 more than that, so let's say .20 more for premium than regular. Let's say that we average 18mpg with our non-hybrid '10RX's. So, figuring it out for 10k miles: 10k divided by 18mpg gives 555 gallons consumed for 10k miles. Multiplying the 555gal by the .20/gal differential gives you a cost of $110. per 10k miles driven for using premium.

So, keep the car for 50k miles and it costs you $550. extra. Keep it for 100k and it's $1100. There are many variables like: you get better or worse mpg, or using premium will give you better mpg, or my premium gas cost differential is more/less, or maybe using premium will keep the car in better shape so I'll have fewer repairs, or what-have-you.

I just used some average numbers and came up with an average cost. Each of us has to determine if that extra expense is worth it to us.

 

I dont want to bore you with the Ideal Gas Law , and the difference between regular and premium gasoline( I am talking about Octane grade and not brand, cause brand wise there are no difference between let's say Chevron or Shell). But the easy and short answer is if your engine is built for regular grade gasoline puting premium gas does not improve it's performance but in high performance cars that require premium gas you should use premium since the reason Higher-performance cars require premium gas is that their engines are designed for higher compression (higher compression = more power), and regular gas may cause knock in some cars but in majority of premium cars these days the engines contain knock sensors that detect detonation and automatically retard the spark to compensate. The delay means maximum gas expansion occurs when the piston is farther along in its downstroke and thus there's more room in the cylinder head. This reduces peak cylinder pressure, eliminating knock but also giving you less power and poorer mileage.

So in short for your Lexus, with Premium gas you get better gas milage and cleaner engine (in most cases). And with the higher gas milage the difference between premium and reglar is not much specially in US when we are talking in galons and not liters like here in Canada!

 

Jclem, You are spot on with the price difference for our area, it runs seven to ten cents a gallon between grades. But I look at it from an English standpoint instead of mathematically. What does it recommend we use in our car's manual?
If a person is concerned about an extra couple of dollars when filling up they are really going to be upset when they realize how much they are losing to depreciation as the miles rack up and time passes.

 

Maybe not where you are but there is a difference in brands here.

 

What do you mean DNC? Unless they are selling lower Octane gas for premium there is no difference. You should get your gas from newer gas stations ( Cleaner in ground tnaks and better filteration system). But other than that, there are no difference. Take it from me I've worked for Exxon for 12 years!

 

Actually, I have never put in what my manual recommends. It states 91 Octane, and I never remember seeing a 91 octane gas available. It runs 87 (regular), 89 and 93 octane for premium. I can't go wrong with 93 octane, but where is 91 actane available? I even thought about mising 89 and 93 to give me the 91, but what am I missing?

 

I am sure you know your job well but if I am understanding you correctly, you are saying all brands of gas are the same. This flies in the face of everything I have ever been told at national car club meet workshops for the past twenty years. A guy in one of these clubs, who owns a small chain of stations, says there is a difference from brand to brand as he transports and buys some of all brands. I can run one premium brand and get spark knock in some of my cars where another will not produce spark knock.
If I have misunderstood you I apologize. If I have understood you correctly I am going to have to disagree.

 

dont mix it! lol 93 is better than 91, but 93 isnt available in all markets. the higher the octane will not hurt the vehicle but can only be better.

I also agree that there IS a difference between brands. Sure, gas is gas and it comes from the same place, but the additives that each brand adds is what is worth the money here. Joes' Gas Stop down the street will probably have an inferior fuel mixture than Chevron or Shell or 76, the name brands. Shell markets their nitrogren enriched gas, Chevron with their Techron, and I dont know what 76 markets because I only use Chevron.

Over time, the additives will keep your engine clean!

 

My question is more philosophical than economical. My point is that Toyota recommends regular fuel for all the other V6 engines that are pretty much the same one as on the RX.