MD727

guys - you either read his question wrong or your missing the point- he's asking if the car requires premium fuel - which it does - now what you choose to put in it is up to you - but he asked what the inside of the fuel filler door says - and it says only preimum fuel be used.

flipside909

Premium Unleaded is recommended due to the fact the 4GR-FSE V6 2.5L is a high compression motor. 12:1 compression ratio is high. Your engine is designed to run with higher octanes to prevent detonation despite the fact of the V6 having knock sensors. You can use lower octane grades for a short period of time, but you will notice the retard in power delivery and obvious sluggish performance.

unit74

iTrader: (3)

Our 330i calls for premium......... For about the last year we have used the cheapest gas we could find. No noticable change in performance.........

I don't buy into the "Gotta buy premium" band wagon. I thought I read somewhere that all cars had to be designed to run on 87 octane gas by law to meet emmisions standards.

Also, I read a study on gas grades and the gist of it was that only a few higher performance vehicles actually saw real improvements over the 87 oct. gas.

I don't have any hard evidence on it right now, but if I can remember where I saw this info, I'll post.

spwolf

you are wrong. as flipside mentioned already, you car has been designed for premium fuel.

articles you read were probably done on cars that were made for 87, so no gains were made with premium, which is normal. However, with lower octane gas in IS250, you will lose 5-10hp and keep in mind that knock sensor works only after knocks are heard - and damage is already done.

unit74

iTrader: (3)

No it included several cars which would be concidered high performance.

But I'm sure your in the same boat as many others, thinking your car needs this gas to run. To each his own.....

paeko73

Why would Lexus post "premium only" if the IS does not need premium? Doing that would probably steer away people who don't want to pay extra for premium grade. Therefore, the IS definitely needs premium to be labeled that way.

gsrthomas

iTrader: (1)

I sometimes fill up with premium and sometimes with regular. Depends on my mood. No harm will be done to the engine if you run it with regular. To each their own though.

My last car said "premium fuel only" and I ran it with regular for 2 years. Ran perfectly no problems at all. Sold it at 200k miles.

rominl

iTrader: (4)

let's figure out how it works......

all cars will run on 87 no problem, unless the car (ecu) is completely retarded. the thing is the ecu will sense that you have lower grade gas and it will retard its timing to avoid pinging, at the penalty of less performance.

if you just put in 87 and drive normally, more than likely you won't feel anything.

however, if you want to "test" it? put 87 in your car, get a super hot day, and floor the car and redline it. look for pinging and how the engine struggle to keep up with the power. that's what you are losing. it's not like you put in 87 and the engine will explode.... we are just talking about different grades of gas here, not like putting water into the gas tank

lexus recommends premium gas for a reason. they (toyota) get cars to run on normal 87, so it's not like they just put up the sticker for the heck of it.

and btw, just a side note, i have no clue why people would go cheap on gas. i mean, on avg driving, over a yr span, you probably pay about 200 bucks more for premium gas over regular..... you are driving a 30k car (using is250 as an example), you should be able to afford that...

just my 2 cents

rominl

iTrader: (4)

one example i can think of is my friend with the wrx. he got aftermarket ecu to boost up all the timing and such for more power (read: noticeable power, not the 2hp increase from exhaust).

anyway, before he flashed the ecu, with premium gas or regular gas he had no problem running the car and even racing it, it's all good. however as soon as he flashed the ecu, he started to get pinging on medium to aggressive driving. normal grandpa driving was ok.

he lowered the timing on the ecu a bit and it helped, but still got pinging noise. finally he tried to mix in some 100 octane racing gas and all the pinging gone.

what does this say? his car WILL run on all gas, but it's all about the ecu timing. he now lowers the timing further and put in 91 and it's all good. but 87 is a no-no with his driving. however, if he drives slow, i bet everything that he will survive with 87

clubfoot

And I agree with rominl. For 10 cents more a litre for 91 here in Canada its worth it to give your car what it requires. The engine runs a nominal 12:1 compression ratio,... I will only put 91 octane in it.

ShooExpert

I agree with Unit 74. Cars for the US need to be able to run with at least 87 octane. Perhaps you'll get a smidge better performance using 93 octane, but 87 octane (or the cheap stuff) won't hurt your car at all. My dad has a corvette that he puts the cheap stuff in and he has never had a problem. It isn't about the money, it is about principal I suppose. To each their own...

4DOORFUN

I agree with the majority of what you said in your two posts. However, I will guarantee that Lexus has not maxed out engine performance on the IS like the way your friend did with his WRX. What I mean is that most mass produced factory cars are not tuned to maximum performance. Auto makers have to tune for some performance, yes, but they also need to meet strict emissions standards set by the EPA. I'll bet you could dyno tune a stock IS 350 right now and see some marginal horsepower gains just by bumping up engine timing a bit and leaning out the air/fuel ratio.

My point is that the IS is not on the verge of pinging right from the factory. Lexus builds in a fudge factor so to speak. Remember, this car is sold across the country to all diffferent kinds of drivers in all different kinds of climates. If Lexus tuned the IS for absolute maximum performance, then someone would eventually report pinging issues. Instead, they back off just slightly from maxium performance to avoid these issues and allow for some wiggle room. It's this reason that premium fuels are typically "recommended", but not "required". Those two words have very different meanings.

flipside909

Corvette V8s aren't high compression nor are they hi-tech (old school pushrod ohv) compared to their import counterparts. I guarantee you that the new IS350's 2GR-FSE Dual VVTi Direct Injection engine with a twin cam setup has alot more technological features than the LS-1 V8 in the Corvette, even more so than the LT1.

Just for point of reference, the 2GR-FSE 3.5L Dual VVT-i V6 in the IS350 has a 11.8:1 c/r and the 2GR-FSE 2.5L in the IS250 has a 12:1 c/r for it's motor. Both engines run high fuel pressure at 1600psi. I doubt any American V8 has even a fraction of that fuel pressure running through it's fuel lines.

flipside909

You'll be suprised how Toyota/Lexus engineers their engines and ECUs. The engines in most modern Toyota/Lexus vehicles are pretty closed to maxed out...which is why it's very difficult to mod a Toyota/Lexus engine without having to alter or switch out the factory ECU for a standalone setup. Have you ever worked on a modern Toyota/Lexus engine and bump up the timing or lean out the a/f ratio? It's not that easy with Toyota/Lexus electronics and engine management. Did you know most of the modern Toyota/Lexus engines have no distributor? Check it out if you have a chance, it's not fun...which is why many aftermarket companies have struggled to produce forced induction systems and simple aftermarket bolt-ons for a majority of Toyota/Lexus motors...including those TRD S/C's released for the Camry/Solara, Tundra, Tacoma and Corolla/Celica just a few years ago just to name a few. They all have problems with the factory fuel injection system as they are almost maxed out in their regular duty cycle with the other factory fuel system components. Can you imagine how much fun many tuners will have with 1600 psi of fuel pressure through Toyota's D4 (Direct injection) technology?

When the label says "PREMIUM UNLEADED ONLY" on your gas door and posted in the owners manual, you should use what the factory book recommends. On my 2004 IS300 (2JZ-GE 3.0L I-6), it clearly states:

This verbage is verbatim from my owners manual. It should be similar if not the same on the New IS' owners manual. Now if you have a 1MZ-FE or 3MZ-FE V6 from the ES and RX, it states Premium Fuel is "Recommended". It's clearly stated which Toyota/Lexus vehicles require Premium Unleaded and those vehicle that can use "Unleaded Fuel Only" but can recommend Premium for improved performance. When I have time I will post the verbage on my 1999 Toyota Solara SE V6 (1MZ-FE 3.0L V6 identical to what is found in the previous gen ES and RX). Remember the IS is a performance/sports sedan with Luxury. It always has and always will be. Now if you want Luxury at an entry level price, that's what the ES330 is for.

4DOORFUN

Whether or not an engine is considered "hi-tech" as nothing to do with it's tolerance for pinging. Pinging is simply more likely to occur in engines with high compression ratios, high engine cylinder temps., and advanced timing. Yes, the IS350 has a twin cam set-up with direct injection. Great, but that has nothing to do with pinging.

My 2000 Mustang GT 2V 4.6L SOHC V8 engine is hardly considered "high tech". However, ever since I increased engine timing and leaned out the a/f ratio, I need to be concerned with pinging. I now run 91 octane fuel. It's still the same old "low tech" engine, but now it's pushed to the limits for the stock fuel system. I was able to grab peak gains of 8 rwhp/10 rwtq. from the tune. Those are not large gains, but my point is there is always something extra left over. The IS350 is no different. BTW, I tuned my car while performing wide open throttle runs on a dyno. It's the only way to do it properly.

If we were talking about a limited production car like a Viper or ZO6, I'd be more willing to bet those car are maxed out from the factory tune.

BTW, I realize the IS350 doesn't have a distributor. Are you kidding me with that?