lexusrus

Yes, I remembered the hp gain was like just a few more horses. But I just follow Lexus recommended premium fuel for the LX570. TO ME, the LX570 just runs smoother. It maybe all in my head.

greeknasty

Since the day I got it I have been putting 93 in my Rx. It was only 20-30 cents extra. Well now all of a sudden its nearing a dollar extra for vpower.. Thats $15 extra every week for a fill up which equals $720 a year or $3600 5 years. I could eventually buy a new engine for that!!
But i wanted to give you my feedback on the change... Bottom line my gas mileage stayed the same and my power stayed the same. I plan on using techron once a year to clean up any potential junk.
So if you are on the fence of using 93 or 87.. 87 is just fine!

Kopavi

I live at 5700 feet elevation and have always used 87 octane gasoline in vehicles that recommended premium (an Acura MDX, Jaguar XK and two RX450H's). I have never had an issue. If I were to drive in lower altitude states, I would likely upgrade to premium fuel. Many people feel more comfortable using premium regardless of altitude and that choice works for them.

The following came for a Popular Mechanics Q&A back in 2010 about driving in Idaho, Utah and Nevada:

​​​​​​Octane is the ability of a fuel to resist knock, and high-compression engines tend to knock more. The obverse of that is that lower-compression engines can run on lower-octane gas. Air is thinner the higher above sea level you go. Less air going into the cylinders means less pressure at top dead center when things go bang. It's a lot like lowering the compression ratio in the engine, reducing the need for high octane. Cars will run just fine on lower-octane fuel when they're well above sea level--and all of those states are. Hopefully, by the time you get back down to denser air, you've burned off most of the low-octane stuff, and can refill the tank with higher-grade fuel.

http://www.popularmechanics.com/cars...a5308/4345737/

lexus114

really? i doubt that..

tus

If you consider that a modern car will keep tuning itself to get the best performance under a specific load, and that premium is only really needed for maximum performance, I could see not seeing a difference between regular and premium during what for most people is normal daily driving. Running regular will "de-tune" the motor, but it still has more than enough power for daily tasks so you would not notice a difference. How many times do you really need max power out of the thing during daily driving? The energy content of regular and premium are essentially the same, it's how the motor is tuned that enables it to get more power.

Now if we go to the track and burn a tank just running 1/4 miles, asking the thing to produce max power all the time, I'd guess we would see slower times and decreased mileage with regular, although the hybrid factor is something I'm not exactly sure how to factor in.

lexus114

i was using regular for a while when i first bought mne. and after a while it didnt seem like it was running to its full potential. so i contacted lexus corporate to see what they recommended. theyre response was to use premium for best performance and gas millage (which they deleted from the owners manual) so i switched to premium and it has never run better.

MikeInOr

It looks like the difference between the 2010 - 2013 engines and the newer engines is indirect injection vs direct injection. Indirect injection = spraying the fuel into the intake manifold and having it carried into the cylinder with the incoming air. Direct injection = spraying the fuel directly into the cylinder. aka like a diesel. A 12.5:1 compression ratio indirect injection engine is designed around using slower burning higher flash point premium gasoline to control the combustion. A direct injection engine is able to control the combustion by precisely timing when the fuel is sprayed into the the cylinder... hence an efficient high compression engine can be run on regular fuel with direct injection.

I am researching my next vehicle. The 2010 450h lines up very nicely on the price/power/mpg curve... for me. The premium fuel requirement dampens my enthusasm a bit. My current car requires premium and I am tired of paying the premium price for premium fuel!

greeknasty

awesome info, any chance you have a source? I've always wondered if any differences but couldn't ever find information on engine changes. I'd def pass this info along to others

raytseng

This is what happens on the internet, where everybody looks like an expert just on how confident they sound. With all due respect, Mike is just making things up on what he feels is right.

I posted on this topic somewhere else, but to summarize:

Regarding the fuel for the RX350, you can look at the Lexus Press Releases to see the differences. There is no mention of an engine change. The difference was they changed the fuel requirements.
Not fact, but just an anecdote that seems true to me, Lexus Salesperson told me it's mainly to improve sales rather than extra technical change.

If you look at the Press Release Documents. You can see their Engine Performance specs when they ran the same engine on 91, and in the subsequent year they ran on 87. As far as quality of source, you would think Lexus/Toyota is going to have state-of-the-art performance testing procedures that far exceeds what any individual person here has. So this is basically the top tier in terms of source quality and trumps single data points..

If he was instead talking about the 450h, you can look up the similar releases,I don't believe there was an engine change either.

Here are real links.

2012: http://pressroom.lexus.com/releases/...oduct+info.htm

Note: All specs are for both all-wheel drive (AWD) and front-wheel drive (FWD) unless otherwise noted. Items in bold are new for 2012.
ENGINE
Type, Materials V6, aluminum block and heads
Designation 2GR-FE
Valvetrain DOHC 24-valve with Dual VVT-i
Displacement 3.5 liter Bore x Stroke 3.70 in. x 3.27 in. (94.0 mm x 83.0 mm)
Compression Ratio 10.8:1
Horsepower 270 hp @ 6,200 rpm
Torque 248 lb.-ft. @ 4,700 rpm
Maximum Engine Speed (redline) 6,400 rpm Fuel System
Sequential Multiport Fuel Injection (SFI) Fuel Requirement
Performance Numbers achieved with 87-octane Unleaded fuel Emission Certification ULEV II (California); Tier 2 - Bin 5 (all other states)

2011:
http://pressroom.lexus.com/article_d...rticle_id=2669

Note: All specs are for both all-wheel drive (AWD) and front-wheel drive (FWD) unless otherwise noted. Items in bold are new for 2011.
ENGINE Type, Materials V6, aluminum block and heads
Designation 2GR-FE
Valvetrain DOHC 24-valve with Dual VVT-i
Displacement 3.5 liter Bore x Stroke 3.70 in. x 3.27 in. (94.0 mm x 83.0 mm)
Compression Ratio 10.8:1
Horsepower 275 hp @ 6,200 rpm
Torque 257 lb.-ft. @ 4,700 rpm
Maximum Engine Speed (redline) 6,400 rpm
Fuel System Sequential Multiport Fuel Injection (SFI)
Fuel Requirement Performance Numbers achieved with 91-octane Unleaded fuel Emission Certification ULEV II (California); Tier 2 - Bin 5 (all other states)

MikeInOr

Sorry, I was referring to the 450h engine... this is what I am considering buying. I never claimed to be an expert, I just like to keep up with engine technology. I always considered it pretty common knowledge that the (modern) way to get good performance out of a high compression engine on regular gas is direct injection. In the 'old days' they would actually inject water or water/ethanol into the incoming air stream of high compression engines to control combustion with lower octane fuels.

https://en.wikipedia.org/wiki/Toyota_GR_engine#2GR-FXE

2GR-FXE

Atkinson cycle, VVT-i, uses cooled EGR system.

For the Lexus RX 450h, the compression ratio was 12.5 to 1. For the Lexus GS 450h, the compression ratio was 13.0 to 1.[8]

Applications (calendar years):

• 2010 Lexus RX 450h, (GYL10/15/16), without D-4S (conventional multiport indirect injection) 183 kW (245 bhp)
• 2010 Toyota Highlander Hybrid, without D-4S (conventional multi-port indirect injection) 183 kW (245 bhp)
• 2012 Lexus GS 450h (GWL10), with D-4S (both multi-port indirect and direct injection) 218 kW (292 bhp)
• 2013 Toyota Crown Majesta

2GR-FXS[[url=https://en.wikipedia.org/w/index.php?title=Toyota_GR_engine&action=edit&section=8]edit]

The 2GR-FXS is the hybrid version of the 2GR-FKS.

Applications (calendar years):

• 2015-present Lexus RX 450h (GYL20/25)[11]
• 2016-present Toyota Highlander (GVU58)

2GR-FXS is a indirect/direct injection engine:
http://papers.sae.org/2015-01-1972/


Direct injection engines require a higher fuel pressure in the fuel pressure rail to function (more costly parts)... the air in the cylinder is already being compressed when a direct injection engine sprays the fuel into the cylinder hence the fuel pressure has to be higher to overcome the pressure in the cylinder. The 2GR-FXS uses both indirect injection (spraying fuel into the in-rushing air) and direct injection (spraying fuel directly into the cylinder). Indirect injection does a much better job of mixing the fuel and air as they are flowing through the intake ports. Direct injection allows much better control over the combustion in the cylinder. Toyota uses both on the 2GR-FXS to achieve good A/F mixing and good combustion control. One big advantage of direct injection is that fuel can be added to the cylinder after combustion in the cylinder has already started... I do not know for sure if the 2GR-FXS engine injects fuel into the cylinder after combustion has started... but I think there is a really good chance that they do. This is how pre-detonation is usually controlled with direct injection... as I understand it.

As direct injection becomes more common and is more widely used the components of the system get cheaper. The original fuel injected engines (70's, 80's) were much more expensive to produce than carbureted engines. After fuel injection became common it became much cheaper to implement. Indirect injection / direct injection is going through the same cost / adoption evolution today.

When I read that the 450h engine was an Atkinson cycle engine (It is not a true Atkinson cycle engine) I assumed it was also direct injection and would run on regular. The Atkinson cycle is where the power stroke is longer than the compression stroke... and doesn't have anything to do with the fuel injection... I have just noticed the two technologies are usually found together (Toyota Atkinson cycle hybrid engines that will run well on unleaded). https://en.wikipedia.org/wiki/Atkinson_cycle I am disappointed to find that the 2010 450h is an Atkinson cycle engine without direct injection and in my thinking should be fueled with the premium gasoline that it was designed for.

The 2010 450h is still a beautiful piece of engineering... just a bit less economical than I had hoped. It is good to know that the 2015+ 450h's will run on regular gas (It is good to see technology advance)... they are just out of my price range.

raytseng

mike youre mixing up production years with model years. there is no change in the 3rd gen rx. the 2015 production year is model year 2016 which is the 4th gen rx.
be advised, don't buy a "2015" and expect it to have the engine improvements you are citing.

MikeInOr

Cool! Thank you for the tip! Unfortunately the only thing I can afford is a 2010... but if a 2015 comes along for a great price it is good to know that it isn't direct injection.

I have been trying to vacuum up all the information I can from this site that I can... I have spent WAY too long reading about seats! Seats are very important to me though!

cblexht

2010 RX350 calls for premium gas. What damage can occur if regular or mid grade gas is used only?

ukrkoz

None.
It calls fro premium gas "for improved performance". Same engine in Highlander calls for 87. Same engine.
It is, also, same engine produce from 2009 through 2015, 2GR-FE with perfectly no difference for the models. Yet, they changed octane rating from 92 to 87 in 2012. So from 2009 to 2011 - it'as premium gas, from 2012 and onward - it's regular. I actually spent my morning researching this and, apparently, outside of "computer mapping" there is no difference. Same compression ratio, same injection type.
Consensus is, you will lose 5 hp. Do you care?

afpj

Haven't seen any reports on forums or nhtsa about "damage". As noted somewhere else in this thread, the computer will retard timing to prevent predetonation, and your bhp and torque output will decrease accordingly.(also as noted in previous posts, it's the same 2gr-fe engine, and the later years have less bhp/torque ratings with 87 octane as the "recommended" fuel). Vast majority of drivers will notice no difference. If you go WOT frequently, you might notice a difference.