xfirechief

I too change my oil, I use synthetic & enjoy the hands on experience.
With the oil I use I go a long time between changes so its not bad at all.

AV8R_BOB

Hi folks,

Yesterday I bought my bride a new RX350 for her 25th anniversary, as a well deserved reward for putting up with me all those years. Looking through the book I see Premium gas is required. I read somewhere the RX350 is based on the same platform as the Toyota Camry and Highlander, so I looked for the fuel spec on those. I could not find the spec on Toyota's web site, but I found several references on car review sites indicating the Toyota burns regular gas. From Motor Trend's data below it appears the same 3.5L V6 is used in both vehicles.

I understand the octane requirement is correlated with compression, but what I don't understand is why the Lexus needs premium but the same engine in a Toyota Highlander only requires Regular.

Lexus ( http://www.motortrend.com/cars/2009/...350/index.html )

- 3,456 cc 3.5 liters V 6 front engine with 94.0 mm bore, 83.0 mm stroke, 10.8 compression ratio, double overhead cam, variable valve timing/camshaft and four valves per cylinder 2GR-FE
- Premium unleaded fuel 91
- Multi-point injection fuel system
- 19.2 gallon main premium unleaded fuel tank 16.0
- Power: 201 kW , 270 HP SAE @ 6,200 rpm; 251 ft lb , 340 Nm @ 4,700 rpm

Toyota ( http://www.motortrend.com/cars/2009/...der/index.html )

- 3,456 cc 3.5 liters V 6 front engine with 93.9 mm bore, 83.0 mm stroke, 10.8 compression ratio, double overhead cam, variable valve timing/camshaft and four valves per cylinder 2GR-FE
- Unleaded fuel 87
- Multi-point injection fuel system
- 19.2 gallon main unleaded fuel tank 16.0
- Power: 201 kW , 270 HP SAE @ 6,200 rpm; 248 ft lb , 336 Nm @ 4,700 rpm

Any experts out there who can explain this?

Joeb427

iTrader: (1)

Yet the same 3.5L in the '08 Camry has 4 less horsepower(268) and a bit less torque than the same 3.5L in the '08 ES 350(272) using premium.
The 3.5L in the Highlander and RX has 270HP.
The RAV4 3.5L has 269 HP.
Same engine with 4 different HP ratings.

I believe the 3.5L has the best performance and MPG on premium.
Toyota would lose sales if premium was required in the Camry,Highlander and RAV4.
I'd go at least 89 in a 3.5L 270 HP.

Here's an article on using regular vs premium when premium is required.

http://www.myride.com/lifestyle/feat...120-page1.html

mandyfig

Use 89 at least, but 93 works better. More HP, need 93.

AM1

iTrader: (6)

you guys can get 93 from the pump? we can only get 91 from the pump without having to go special gas stations.

banjo

Yup, 93 is the top grade here in Texas...

Joeb427

iTrader: (1)

93 in Jersey.
91 at Sunoco only,I believe.

AV8R_BOB

"The 3.5 has the best performance on premium"? The point is the Highlander and Lexus engines appear to be identical and both get the SAME performance (HP and torque, at identical rpm's) even though one burns regular and one premium. That defies logic.

I suspect some marketing monkey business. Selling the Toyotas they know a premium gas requirement will cost them sales. So they design it to run on regular and specify that. Selling the luxury brand they figure specifying premium will make the buyers think they are getting a higher performance vehicle, and will INCREASE sales.

I already understand the points in the article you referenced...
But my point is I'm questioning whether the Lexus actually does require premium. It appears it's the same engine used in two different cars, achieving identical power in both cars, but one requires regular and the other premium. Therefore if the Toyota achieves rated power on regular, why not the Lexus? I was hoping someone could provide a logical explanation why the Lexus requires premium to achieve rated power but the Toyota does not.

Joeb427

iTrader: (1)

Then why is it that the exact same engine has 3 difference horsepower and torque ratings?
The best thing to do in my opinion is go by what the vehicle manual recommends.
As far as the soccer mom RX or the ES350,I believe having those models require regular would not hurt sales.In fact,I believe sales would go up a bit.
Cadillac's 263 hp 3.6L requires regular fuel as well as the $42K 368 HP Hyundai Genesis.

AV8R_BOB

Could be 3 different dyno tests... and 3 results. If you take the same model engine and take 10 of them off the assembly line and run dyno tests, you are not likely to get the same exact results for all 10. There will be some variability.

Joeb427

iTrader: (1)

Why?
They're all made to the exact same specs and bench dyno'd.
Wouldn't engines in the same model then have different HP?

AV8R_BOB

Yes, that's what I'm saying. No two engines will be exactly the same due to the variability that always occurs with any manufacturing process. There is also variability of the test equipment.

The very small differences in HP and torque you listed for the different Toyota 3.5's could be due to the above.

AM1

iTrader: (6)

for the record, my service advsior has said it is ok to run 87 in the RX models including the rx350. otherwise i have no comment whether or not this is what should be done.

AV8R_BOB

I asked the Lexus sales rep (Mark Krueger at Safro Northshore in Milwaukee) to get me an answer, here's his reply:

Sorry, but that sounds like BS to me.

Facts:

1. The Toyota Highlander and Lexus RX-350 have the same engine.
2. The Highlander 4WD weighs 4321 lbs and gets 17/23 mpg with REGULAR
3. The RX-350 AWD weighs 4090 lbs and gets 17/22 mpg with PREMIUM

So the Highlander has the same engine producing the same HP and torque, is a heavier vehicle, running lower performance gas, but gets BETTER mpg ??

But according to Lexus if I run the same gas in the RX-350 the mpg and performance will suffer?

That makes no sense.

Hence my suspicion this is all about marketing.

As an engineer I need a better explanation than what I've been seeing as to why the RX-350 needs to run premium. None of what I've seen so far makes logical sense.

Joeb427

iTrader: (1)

Maybe because Lexus engineers recommend premium.
Just use 87 and be happy.
My RX is leased.
I use 89 and an occasional 93 fill.
My GS is a purchase and I use Shell 93.
Don't tell me you would use 87 in a GS.
Even you wouldn't.
There isn't a Toyota model with the exact same engine.