jfelbab

Ethanol is awful stuff for mileage. Cars that use e85 get 20-25% less miles per gallon than those burning pure gasoline. This is due ethanol's having less energy per volume. You may have noticed e85 costs the same or slightly more then premium fuel (if you can find it) but you get a huge reduction in mileage. Performance also suffers. With e85, instead of getting 300 miles on a tank you will have to fill up after 225 miles. With e85 instead of doing 0-60 in 7 seconds it will take you 9 seconds.

Another problem with ethanol is that it is in very short supply. Since MTBE was banned all the gas that used to use that oxygenate now must use ethanol. Currently, there is barely enough ethanol around to keep up with the e10 grades much less e85. So what happens when we have a drought and the corn crops dry up? Prices will soar and supplies dry up. Remember the gas lines?

E85 is a poorly conceived alternative to gasoline pushed by ag interests.

JorgeGVB

That's pretty disappointing to here. I was not aware of these issue with E10 and E85. I never paid much attention to it before, so I wonder if there is any non-ethanol gas in my area. Now I am really interested in knowing if that is the problem with my poor gas milage. The bad thing is I just filled up 2 days ago with E10, so now I will have to wait about another week or so to find other brand of gas.

pkat

I've had my RX350 since December. I started using low octane, but then started alternating with high octane.
Does it really make any difference which octane to use? I live in California and I don't notice a difference.

jamesfabin

I only use 91 octane - it's what is recommended and what the system is designed to perform its best with. Using a lower octane gas will have impact on the overall performance of the vehicle - which if you wanted a lower performance I would recommend going with the Hyundai Santa Fe (it'll not only save about $5 at each fill-up, but cost less to purchase).

My recommendation (and that's all it is) is to stick with the 91 octane recommended. You're not going to save much going with the lower octane - and you wont gain going with a higher octane. There have been discussions on here before where people felt they were waisting money using 91 octane gas, but to those I say you should not be driving a Lexus if you can't afford the additional $15 a month in gas.

James

AM1

iTrader: (6)

if lexus did not want you to use 87 at all they would not have left that option up to you. i still use 87 in my car. and the whole thing about not saving money by going with 91 octane? if you add it up over a year it really adds up. around here the difference between 87 and 91 ocatane is around 20 cents. suppose you use 25 gallons of gas a week, in a month that equals 20 bucks saved times 12 which equals 240 dollars a year saved, chump change huh?

pump142

We use the 87oct in the RX. Way cheaper and the 91oct doesnt seem to show any difference mileage or performance wise.
My GX requires the 91oct and the cost difference is noticable.

dhamaka127

I have used 87 Octane in my engine one time because this idiot at the pump put it in. With this i did feel a performance difference and also difference in gas mileage!

So I mainly stick with 93 Octane because the 91 is harder to find.

IMO....if you can afford a Lexus...you should be able to afford the gas!

RC_Av8r

When I purchased my vehicle the salesman told me that he uses 87 in his RX and it runs just fine.

I have tried 91, 89 & 87 in my RX 350.

I have not noticed any performance loss with the lower octane fuels but then I don't have a lead foot either. I usually drive with the Trip Meter on the main screen and try to peg the yellow line as much as possible
The best MPG I got was with the 89 but it may simply be the result of that weeks traffic patterns. As they say, "Your milage may vary"

Overall I think 87 is just fine.

BTW, it's not a matter of being able to afford 91, but if I get the same results with 87 then burning hunderds of dollars a year is simply wasteful. However, those of you who feel that just because you own a Lexus can afford the extra $$$ can also "afford" to send it to me
I'll give you PayPal address....

I guess my point is: Don't waste the extra money simply because you can afford it; do it because you really feel it is a better choice or because you want to.

Dave

notme

87 Always have and always will.

AM1

iTrader: (6)

i agree there if you people can "spare" so much $$$, paypal me some $$$ too. man i must be doing something really wrong i put 87 octane in my rx and i put the cheapest gas possible, i hope lexus doesnt void my warranty

coolhand

I've also tried with 87 and 93... no difference at all.
I use 87 and it's real plus!

Sugar3d

Unless you are racing or are worried about knock (which is a non-issue in newer cars) 87 should be fine.

BBHanks

I couldn't tell any difference between 87and91 oct. If I really wanted the higher octane I would go with the 115/145 AV gas.That will make the tail pipe light up at nite..

asianrage

For me, it's not about price. It's about preventive maintenance. If the manual says we should use premium then use it. Can you guarantee that it won't affect the engine performance? Are there scientific proof(s) that using regular unleaded will be the same as using premium? Yes? no? I'll just keep using premium. If price IS a concern, then you can fuel up with unleaded Arco

geko29

There are scientific proofs, but I'm too tired to look them up right now. The short version of it is: Octane is a resistance to ignition. Ergo, higher octane fuel is more difficult to burn. In high temperature, high pressure situations, this can be a good thing because it can prevent preignition (knock). However, it can also be a bad thing, because the fuel can take too long to burn completely and not deveop the power that it can.

The maximum power, fuel economy, and engine longevity is ALWAYS achieved by running the absolute minimum octane that an engine can take without knocking. However, modern engines have knock sensors that detect knock and retard the timing, and the driver will usually not hear it. But retarding the timing will ALWAYS reduce fuel economy and power. Therefore, even if you don't hear knocking, if your gas mileage goes down or your car accelerates slower when filled with regular, the octane rating is too low. On the flipside, if switching back and forth between regular and premium (as I have done several times in my own RX350) shows no change in economy or power, then filling with premium is paying for octane that you quite simply don't need, and actually does more harm than good.