Droid13

Untrue!! It can have a strong emotional effect. For years I struggled to come to terms with the little angel and devil on my shoulders, one telling me to fuel up with premium because that's what is good and right, and the other saying screw the gas companies and their massive extra costs for premium fuel (especially here in Canada) that do little. They kept me up at night fighting each other, whispering their messages deep into my subconscious. I could barely fuel my vehicle, I'd shake so intensely I could barely put the nozzle into the filler tube. Some days one would win, some days the other. The day came that I went berserk at a gas station pounding both my shoulders with the windshield squeegee, children in the cars were crying, the teenage cashier hiding her fear behind her phone, that I decided to attend fueler's guilt anonymous. Now I am free to live my life, I slam that regular nozzle straight in that it barely touches the filler, look up at the gas company logo sign and salute it in the most customary way.

riredale

So glad you found FGA (Fueler's Guilt Anonymous) but it's important that you attend meetings regularly to keep the devil from your doorstep.

FGA is closely related to SCBA (Starbucks Coffee Bigots Anonymous) wherein those afflicted insist that it makes perfect sense to pay $4 for a cup of joe.

kennylexsc

Hi,
Does 12 or 13 RX 350 required regular 87 or Premium gas?

I am looking to buy 12 or 13 RX 350

all advises and inputs are really appreciated.
Thank you very much

ukrkoz

Starting 2012 Rx runs on 87.

Regular Unleaded Fuel Requirement – 87 Octane

Lexus CT 200h – all model years (2011 – 2017)

Lexus ES 300h – all model years (2013 or newer)

Lexus ES 350 – 2012 or newer model years

Lexus NX 300h – all model years (2015 or newer)

Lexus RX 350 – 2012 or newer model years

Lexus HS 250h – all model years (2011-2012)

takeshi74

Replying to an old post in this this thread but since the thread was bumped with other new replies:

Same engine but valve timing is different for the 450h as it runs on the Atkinson cycle. I'm not saying that this means that it requires 91 octane. Plenty of 450h owners have run on 87 octane without adverse affect. Just explaining the difference.

See also:
http://blog.lexus.co.uk/atkinson-cycle-engine-work/

This Motor Trend article claims:
It may be that the 91 octane recommendation is made to offer a "safety margin". I don't know enough on the topic to really say if that's it or if there's more to it.

tempestv8

I would tend to agree with that Motor Trend article - I have a Scangauge II which I use to monitor engine revs, since the hybrid does not have a tachometer.

At most highway cruising speeds, the engine revs extraordinarily low at around 1200-1300 rpm on long flat stretches. If it were a normal engine like the RX350, this sort of low revs would be akin to lugging the engine (low revs, high load) and most normal engines would be suceptible to highly damaging predetonation (aka pinking/pinging).

So I would only fill up the car with premium fuel. Happily, the cheapest fuel available typically in Australia is unleaded E10 (10% ethanol) - this fuel has the right RON level for the Lexus. Cheap and good! And good for the environment as ethanol is a renewable source of energy.

riredale

Many folks would say ethanol is/was an idea that seemed good at the time, but now is considered a wash at best. Farmers vote, though.

As for the old fuel debate, engines for decades have used a knock sensor that will slightly retard the timing if knock is detected. Because of this, lugging won't hurt anything on modern engines. You will lose a very small amount of horsepower on regular. Knock sensor is also used in Atkinson engines, which use a higher expansion ratio and which are thus slightly more efficient. And certainly a higher octane will allow for a slightly higher peak combustion pressure.

Interest tidbit about the hybrid running so slowly, but if I were a computer controlling the system that's what I'd do. The whole idea is to try to avoid a high manifold vacuum because that's when an ICE is horribly inefficient. The computer completely shuts the ICE off when you take your foot off the gas on the freeway, then instantly fires it back up when you need power a few seconds later. Elegant system.

tempestv8

With the high cost of gasoline these days, I've gone back to 91 octane to save some money.

This evening, I was driving up slowly up a fairly steep hill and going past some houses with high brick fences with my windows down.

To my horror I could hear slight pinging noises from the engine which I couldn't hear with the windows up, due to the sound insulation on the Lexus.

I immediately filled up the tank with higher octane fuel. No more regular unleaded for me.