Dmaxdmax

Did the octane requirement change because it's a new engine, or because they evaluated the conditions differently?
Or something else?

iolmaster

iTrader: (1)

In my opinion ( and it is just that) it was the marketing attitude changed. I had always been told by the people at the Lexus dealerships that they put regular in the cars that had the premium or mid grade "recommended". This did not apply to the cars that had premium required. I have always used regular in all my Lexus cars other than my SC430. I have had three RXs 1-3 generation and one ES. I never had a problem with regular. The gang in marketing decided that people were more interested in the cost savings vs. thinking somehow the Lexus was special and needed higher octane gas. I do not think there is any change in the engine that prompted the change in the gas recommendation.

Clutchless

Nothing changed except the marketing folks as mentioned above. If you look up the engine specifications the 2011 with premium gas is listed as 275 horsepower. The 2012 with regular gas is listed as 270 horsepower. The 5 horsepower loss is explained by the change in gas and the knock sensors then adjusting the timing for the lower octane with a resultant loss of power. Most folks are unable to detect a loss of 5 horsepower in an engine with that much power. Most hardly ever push it hard enough to utilize all of them anyway!

byadg

When teaching me to drive, my dad was insistent on a few things, one of which was avoiding fast acceleration and heavy braking. I internalized this pretty solidly so while I’m not an ol’ Granny behind the wheel I definitely don’t use all of the horses at my disposal.

I’m sure that you guys are correct in assuming that the fuel required was a marketing decision rather than engineering.

Droid13

Toyota has been doing this for a long time. Back in 2003 I bought a new 04 Sienna which wanted premium fuel and was rated at 230hp. For the 2006 model, same 3.3L engine, they changed the rec to regular fuel and dropped the HP rating to 215. Actually, thinking into the distant past, I believe its 16 yrs old this week and after ~ 260,000km / 160,000 miles of using regular fuel the engine still runs well, has never let us down and doesn't need any oil added between changes, even though we treat it quite poorly these last few years.

Maybe not coincidentally, my 04 Sienna was also the 1st year of the new generation, so perhaps the marketing folks were eager for some better specs for the launch, but once a couple model years had passed it wasn't so important anymore. The RX seems to have followed the exact same pattern.