patrickkv2

If I want to drive normally and not drive that fast, can I just get regular gas?? I heard you should get premium gas ONLY if you using the performance alot.

HanaleiISF

Sometimes I wonder if people shouldn't be driving the 3IS in the first place if there is a debate on the merits of minute fuel savings. But to answer your question, I believe other have posted that when you use regular gas performance goes down as well as gas mileage, so the savings are muted.

LexSense

iTrader: (2)

Engine detonation/misfires can occur at any given moment regardless of speed or how hard you are pushing the car.

The higher octane you use, the less chance of that happening.

While you could use regular gas, you'd probably get worse gas mileage due to the engine timing retarding itself to accommodate the lower octane when it detects such occurrences.

Definitely go with premium if you don't want a retarded engine lol!

evident

just use premium. filled my car with 87 once by accident and it drove like crap and got worse fuel economy by 1 to 2 mpg.
so it's not even a cost benefit to do. if you cant swing the cost of premium vs regular gas , maybe you should get a v6 accord. they are pretty fast , get good fuel economy and can run regular

SOLEJDM

You gotta pay to play.

tea

if you wanna use regular, go ahead and use regular. It's your car, who cares what Toyota engineers recommend right?

LexusFirst

The user manual has stated the reason for using premium gas.
I am not Trying to insult you. However, if you are worry about the cost of gas, you probably get the wrong car. A Toyota would be a better choice. I don't see how gas price is a concern for Lexus owners.

CtSFox

If you use regular gas, you increase the probability of developing a carbon buildup problem in your IS 250

Loe

if you are simply cruising, regular is fine. In fact, since lower octane is easier to ignite, you may actually find an increase in mpg as it has to work less hard. However, you will see a decrease in performance/acceleration once the ECU pulls ignition advance; because of this, you will more than likely compensate by giving it more throttle, which will trigger the ECU to dump more fuel to meet your demands.

dnasians

iTrader: (4)

Higher octane MUST be used to prevent pre det.Your engine will be pinging/knocking like crazy to try to protect itself. Saving a few bucks here and there will not be enough to cover the knock damage.

If you wanted to save on gas, you shouldn't have gotten a V6.

shirosan

OP, I agree with what others are saying in this forum. It ultimately comes down to protecting your engine in the long run. YES, the ECU will retard the timing to adjust for knock and misfires, which results in poor performance and gas mileage. You may save some money but you are now playing a game of "risk."

If you did use a lower octane I would recommend using an octane booster to meet at minimum 91 octane (even though I believe the car should have 93). That's your best course of action or just keep paying for the high octane like the manual asks.

One good this is that these (current) cars are naturally aspirated (NA) so your chances of damaging your engine with lower octane will be much lower than putting 87 octane in an Evo or WRX lmao.

A2BLexus

I hear that diesel is cheaper than gas. Just go with that.

Just kidding.

Premium or nothing.

azmojo

Modern engine computers can compensate for crappy or lower quality gas. But your engine and the computer is designed for premium. This is not a scam to get you to spend more on gas.

EJ255t

why would you put regular gas in a lexus??? just why???

you don't save that much in MPG, you might actually end up paying more when something goes wrong because you wanted to use cheaper gas.

STICK WITH PREMIUM!!

ModInJapan

iTrader: (5)

Lexus recommends we use premium gas and we should to protect our engine and to allow it to perform at its best potential. You want to give your car performance gas so it performs like a performance car!

-Josh