lgb0250

I've used nothing but 87 octane in mine since the day I bought it with no problems whatsoever. You don't need to do anything to it except put the gas in the tank and go. On 87 octane I've averaged almost 29mpg over the last 4 years.

jcat_350

I'd like to know what your city/highway percentages are to get 29mpg. If it's any less than 75% highway, I'm sorry, I don't believe you.

The only thing that needs to be done to allow for regular fuel is to allow the computer to adjust the spark timing range. Lower octane = more potential for predetonation = the computer must retard timing to compensate. The reason the other models don't say they can run on regular is likely because the engineers set the low end of the threshold on the edge of where regular fuel would knock.

Chances are for every day driving the car will run just fine on regular. But if you dyno the car on regular vs premium, it will make more power and torque on premium because of its ability to advance ignition timing.


Personally, I have run 89 octane in every lexus I've ever had that called for premium and never had any issues whatsoever. I had a 2006 E500 4matic that I never ran less than 91 in because the system operates differently. My father had an 01 CLK55 AMG that he mistakenly put 89 in once, and those cars are tuned so tightly that it couldn't retard the timing enough, and the car started to ping. Brought the car to the mech, drained the tank down to a gallon, went to fill it with 93 and some fuel system cleaner, car ran just fine.

Hell, even Maximas over the years (all the way back to my 99 that I had) called for premium fuel but would run fine on 87 or 89. Those cars, however, didn't have the upper range to advance timing enough for 91 or higher, so while it would run ok, it wouldn't take full advantage of the better fuel.

The one caveat in all of this is forced induction. No matter what, any forced induction engine should never see less than 93 octane. I owned a supercharged 98 Cobra that I always ran on 93. Wouldn't even think of going lower than that. However, one night when I was down to a quarter tank or so, which in those cars I think was about 3 gallons, I stopped by the local speed shop and put 3 gallons of C16 in it (117 octane race fuel). My god it was like a different car. But that was because the supercharger tune had the room to take advantage of it.

christcorp

As I mentioned in the similar thread to this; each car is different and unique. It will never hurt; cause damage; or make you go broke; to try a couple take fulls of each grade of gasoline. I live in high altitude, so 85 is available here. (Basically, the same as 87 at lower elevations). My daughter's Suburu sputters and pings. My Ford explorer couldn't care less. My wife's RAV-4 runs fine but gets lower gas mileage. When we tried 87, 89, and 91 in ALL our vehicles, some noticed a difference and some didn't. Turns out; my daughter's Suburu outback sounded the best, ran the best, and maximized MPG with 89. My explorer doesn't care, so it get's 85. My wife's rav-4 ran identical with 87 and 89 so she using 87, My lexus sounded best, ran the smoothest, and got the best MPG with 89 and 91. But 89 is hard to find here, so I go with 91. And where I live, the price difference between 87 and 91 is $0.10 per gallon. Roughly $1.80 per TANK. So for me, it's worth the extra dollar.

But again; each vehicle is different. If you listen to your car, it will tell you what it wants. Do base your decision on what someone else puts in their car. You spend good money on a Lexus; use what it wants.

FWIW: On a side note: I notice too that in the summer, if I want to, I can usually drop down an octane level. Not because of the COLD VS HEAT. But in the winter, they use a different gasoline/ethanol mixture. This is very common across most of the United States.

Rogarven

We don't drive that much and alternate between my car and wife's 350. Before we bought the car, we discussed it and determined that it wasn't going to cost us that much and if it keeps the car in better condition and gives more power, then it is worth it. If we only fill up once a month, not that big of a deal. We plan on keeping it at least 12 -14 years, just like our Hondas.

kewl

And what, exactly, says you can't use regular now...?

lgb0250

Frankly, I don't care if you believe me or not!

I was off slightly. The car has averaged 28.2 since it was purchased in Nov 2009. For the first couple of years it was probably 80% highway but when my wife retired a couple of years ago it flip flopped over to about 80-90% back road driving. Although, we do live in the country so it's not a lot of stop and go.

Unless you really need the few extra horsepower and torque using premium or even mid grade give you, anything more than 87 octane is just a waste of money IMO.

rickster9

Thanks lbg 87 it is. My computer says 18.5. Are you basing your numbers on the "computer mpg"?

lgb0250

The 28.2 comes from the computer but I do occasionally check it manually whenever I'm on a road trip or say I pretty much drive a whole tank on nothing but back roads. Manually I've come up with from between 24-30, depending on whether back road or all highway. Keep in mind though, this is my wife's car and she's definitely not a lead foot! Good luck.

christcorp

Rick. Have you tried 89 or 91? Just because someone else's car runs a certain way on 87 doesn't mean yours will. Doesn't mean it won't either. But spending a couple of insignificant dollars to see what yours likes can save you a lot of money in the future. A car isn't going to blow up or break down because you use one grade of gasoline over another. But choosing a grade of gasoline because others say they do, isn't the right answer either. Bottom line is, did you ask your car what it likes to run best? Until you do, it doesn't matter what 1 or 50 people say they use.