JP250

So my my 2008 IS250 has had regular gas for all its 70,000 miles. so now i am making a switch to 89 octane gas because i want the engine to last longer. my question is: do you think there are any damaging effects to the internals of the engine from using 87 octane gas its whole life? does anyone recommend any maintenance i should perform at this point? such as cleaning the fuel injectors etc.

shadowman

iTrader: (2)

Why are you even running 89 octane to treat it better? Didn't the manual and the gas door say use "Premium" only?

IN the short term, it shouldn't be too harmful. Since the car is smart enough to detect knocks and pings in the cyclinders and retard the timing. As result, you get less HP and performance out of lower octane gas. You'll also be taking a hit on the MPG. As Kurtz mentioned earlier, this is a endless cycle until you put in the correct octane gas - Premium 91+ Octane gas. Long term, is unknown and it may even agitate the carbon build issue which the IS250 already has.

You're driving a Lexus but can't shell out the extra 5 bucks a gallon for the recommended octane gas...

EDIT: 87 and 89 is no difference on our cars because it was designed to run optimally with 91 octane. You might as well keep running 87 octane

06isDriver

thats a total of approximately 260 dollars a year in "savings" by going with 87over 91, and by savings, I mean reduced WOT power and potential long term issues.

I'd say it isnt worth it.

CANDYAPPLE

iTrader: (1)

lol, that poor knock sensor, probably gonna die soon from all that knocking it had to stop. but to answer your question, yes moving up in grade will be very helpful for your car, might even feel the difference once you put 93.

bob4256

iTrader: (17)

If you wanted the engine to last longer, you should have used premium. It says "Premium Only" for a reason

heyarms

iTrader: (5)

I suggest sugar water over 87 octane.





Seriously, make the switch to premium like the fuel door says.

Squirrelz

You're not saving anything going 87 if you're taking MPG hits from using 87. Savings are a wash. You shot yourself in the foot OP. Get back on 91 or sell the car and get something designed to run 87.

Hoovey689

iTrader: (16)

this

anthrax144

Are you experiencing any of the problems noted with the carbon build-up from direct inject engines? Hesitation, rough idle, etc? If not, then you don't have anything to worry about. However, I'd question why you would even make the change at this point. Either switch to 91 or stay at 87. 89 isn't going to make one bit of difference other than save you $1.50 a tank over premium.

At this point, premium has never been more affordable. When 87 octane gas was $1.00/gal, premium was $1.20, a 20% difference. Now with 87 octane at $4.00, premium is still only $.20 more, a 5% difference. I've actually been seeing premium at only $.15 - .17 difference recently. You are quite possibly getting greater than 5% decreased mpg's by using 87 octane. At this point, there is ZERO justification for using a lower grade gas than what the car was engineered for.

JP250

thanks for the responses guys. its actually my GFs car but ive been driving it a lot more often than my car right now, which i feel like im obligated to maintain it now. i have a lot of learning to do on this car. i did not know it needed premium gas . yikes!

p0lo8

Running lower grade than 91 you are not saving any money at all. Decreased performance, decreased gas mileage and potential problems that can cost you a lot. There is a reason why people who made this car state that it needs 91 octane gas.

ibidu1

iTrader: (1)

Running 87 is perfectly fine! Just because you increase the octane does not necessarily mean you will have added performance. Theres a lot more variables in fuels then just checking the octane levels.

KillaIS250

iTrader: (1)

Running 87 is not "perfectly fine"

The engine, ECU, etc are all designed to run on premium for optimum performance. That's why there's a sticker that says to use Premium fuel.
They didn't put it there for giggles.

Running 87 will just reduce performance as the knock sensor kicks in and the car compensates for the lower octane fuel. Probably not good at all long term for the motor either...

Toymota

I have a similar thread comparing mpg on 93 and 89 octane: https://www.clublexus.com/forums/is-...ctane-gas.html

I got similar replies, but most of the negative ones didn't really have much scientific backing.

My belief is still that running lower octane is okay and there is no difference in mileage as long as the engine does not knock. Whether it knocks depends not only on the design/tuning of the engine at the recommended octane, but also on how you drive it and the conditions such as temperature and atmospheric pressure, and many other factors. Because of these variables, some people can get away with running 87 octane under restricted conditions, while other people can't.

If you accelerate hard such as in city traffic, or desire maximum power from your engine, you may get knocking on anything less than 91 octane. You need to be careful because you may not know that the engine is knocking. There is a knock sensor that will retard ignition and prevent further knocking, but only after knocking has already occurred. Only when it is really severe will it trigger the check engine light. Also, when the ignition is retarded, the engine produces less power, so you may compensate by pushing the gas pedal harder and your mileage will be worse.

So if you don't want to worry about everything I just said, or risk it, just run 91 or higher octane.

VIS250P

iTrader: (1)

Good luck bro.....