alrozrc350

Hi All,
I have been using 93 Exxon premium gas in my RC 350 sport per the documentation, is anyone using any octane lower then this, say 89?

snoflewis

wouldnt even consider putting anything lower than 91 octane. dont see a single reason to.

PAPI007

Nope, Always use Premium!

lexual_rc

I would definitely not try using anything less than the recommended octane rating specified by Lexus per your particular vehicle/model. I have heard on multiple occasions from techs that say that 'pumping a higher octane rating from the vehicle spec recommendation also makes no difference and is a waste of money'...although I'm not sure how true that is since I am not a chemical engineer or done my own research on the same. I tend to fill up at Sunoco which offers a 91 octane rating which is the recommended fuel for the 2015 RC350 AWD as some of my previous vehicles and had no issues whatsoever as well as engines run over 200K miles. However if I am need to pump elsewhere, my only choice usually becomes a 92/93 octane rating as this what most other gas stations offer. Again, this has also never caused me issues in the past. I hope this helps, good luck!

alrozrc350

Hi All -Great input here, I ma staying with the 92, don't want any issues down the road, the car is only 8 months old.

Pittsy

15RC350F

Pretty sure that's made for engines specifically tuned for it. But it's your money.

BraunRC

My dad was told by a salesman at the dealership that he could put Regular (87) in his RX350. He did for many years with no issues until one day I noticed the 'Premium Unleaded Only' sticker on the fuel filler door while my dad was topping off. He switched to Premium (91 only in CA) and got some smoothness and power back. Who knows what kind of long term damage he did, but a tank or two every now and then (if you absolutely have to) probably won't hurt anything long term.

LEXUSGREG1

octane helps gasoline fully ignite and burn, more octane the better ignition of fuel

nelBi

what year is your dads RX350? I'm almost positive the newer ones all can use 87 octane gas.

louczar

Only Super Unleaded (91 or 93 Octane) for me. The octane level depends on where I am as I travel a few times a year through many states.

Last year while traveling through AZ, I stopped at a gas station that had performance fuel and they had 100 octane. Having owned sportbikes most of my adult life (and had done many track days), I have purchased 105 octane a couple of times at one of the tracks I used to go to for my ZX9R. I could feel the power increase. But, I never added that kind of fuel to an empty tank or did I add more than 1 gallon. Just a bump up in octane for a bike that redlines @12K. I doubt our cars would get any real increase in power and would rather save my money...

tfischer

The stations near me only offer 89 and 93, so I have been using 93 for over 4 years, although sometimes, at the 1/2 mark, I will add half a tank of 89 to my 93. This gives me a tank of 91 and saves me a few dollars, but not much.
My understanding is that extra octane is not harmful or helpful, just a bit more expensive. Lower octane will cause the engine to make some accommodations to prevent harm (I think it retards the spark), but the result is a bit less power and a lower mpg, offsetting the lower cost.

Pittsy

I really only did it once for giggles. Not sure if it is because of the fuel or i just got lucky, but my exhaust popped a little more on decel's than usual. Seems it would be the opposite since more octane equals a more complete burn and thus less fuel to ignite post exhaust cycle. Stuff was expensive!

BraunRC

His is a 2010. That could explain why he was told that by someone at the dealer, but the sticker on the fuel filler does say premium only.

redspencer

iTrader: (1)

You can use 89 octane but it will result in a lose of performance. Running 89 octane will lead to more knock/detonation inside the engine and in turn the Knock Correction Learn Value (KCLV) will lower (which will cause the ECU to pull back ignition timing until no additional knock is detected).

A similar thread was recently discussed on the 3rd Gen IS sub-forum and the OP did multiple WOT pulls using different grades of octane to verify that ignition timing is worse when running less than 91 octane: https://www.clublexus.com/forums/is-...d-f-sport.html