I was reading another thread on here, and I'm looking into getting an IS300 myself...My main question is....Can I use regular gas, and what would the downside to not using 91 octane be?

 

Personally I think the entire gas question is very opinionated. Octane level was a much larger issue with older engines but with newer motors there are a lot more sensors and fail safes to keep the engine from miss-firing. IMHO I don't think it is absolutely necessary to put 91 octane in your car unless you plan on going turbo with your IS. The IS really isn't running high enough compression to where putting 87 octane will be detrimental to the engine. I personally just alternate between 91 octane when gas prices are not as high and 87 octane when gas prices go crazy.

 

/\ could not agree more. I run 93 in my supra all the time because of the turbo. On the IS its straight 87 averaging 24 (23.8 mpg on the last fill up) with no ill effects. If it doesn't ping I don't see a problem.

 

I think it retards the timing myself, so you don't have all the power. So yes you cold run regular gasoline, but I wouldn't unless money is a real issue. Remember your engine is a in line six cylinder, with valve timing, Supra engine without the turbo. stright sixes are not around anymore except for BMW's. I would not run low gas in such a advanced engine, while I would with a plain v6 like in the Es300 for example. Just my thoughts, go with what you think is best.

 

lol...sorry but the 2jz-ge engine is not a super advanced engine. It was created almost 20 years ago. Also, you cannot retard the timing by putting different gas in your car. In order to alter your timing you must actually adjust the position of your cam gear.

The inline six has been virtually phased out by practically every auto manufacturer because it is more inefficient compared to the V setups. All 06+ Lexus are V setups, all new BMW's are V setups, all Ferrari's are V setups, etc.

Lastly the 2jz-ge engine and the 2jz-gte engine are not the same engines minus the turbo. The only thing really identical between the supra tt engine and the IS motor is the block. The supra tt engine has a different bottom end, different cams, and the compression is lower since it was built with a turbo. I believe the supra tt was 8.5:1 and the IS is 10.5:1.

Sorry to burst your bubble, but these are the facts.

 

Ok you are right about the supra vs IS engine facts. Just two things I think you are wrong on. The inline six is not an inefficient design for performance reasons, it was phased out by the Japanese manufactures because of emissions and cost. For Japanese car fans the 2Jz of the Supra turbo and the RB26 of the Skyline GT-R are the best engines ever, because of strong internals compared to the V6. Many have built 1000hp cars because of this. Also BMW still uses the inline six, right now in the 328i and 335i, 128i and 135i, and the 528i and 535i. Also the straight six is in all Z4’s. Tuners are trying to unlock the secrets to the 3.5 BMW inline six with twin turbos and once they do, tuned BMW turbos will be one of the biggest tuner cars. As for the original question- just use the gas you think is best.

 

Sorry I should rephrase that its more the amount of space a I6 takes up relative to a V6 for a FR setup.

 

Timing will be affected if the vehicle decides the octane level is insufficient and will retard timing even if its not enough to cause a knock or ping so youre wrong there. I've seen the effects of low grade gas on valves before in 2J's so do what you want but you will pay in the long run. If Lexus and Toyota thought it was ok to use low grade fuel they wouldnt put labels on their vehicles warning you to use premium. Cheaper fuel would be a selling point, dont you think?

 

use e85 its good shizz

 

Its hinders performance. I mostly run 93 OCT but sometimes I run 87 or 89 if im low on gas and the nearest gas station is MORE expensive than my resident gas station. Personally, I prefer HESS.

Back on topic. When I do put in 87 I can feel the car working harder at acceleration. It picks up slower. At 93 the car accelerates quicker and easier.

the manual says to run min of 91. Its usually best to just adhere to the owners manual. Im pretty sure the engineers know what they're talking about. If 87 was sufficient im sure they would have just said to run on REGULAR. I think even the inner gas cap says PREMIUM fuel only.

 

I keep telling my brother to run 89, but he insists on running 93 and to sit around in D.C. traffic. No point IMO. If it were turboed I would say definately.

My first Legacy GT required 91 min. I always ran 89 and it did fine. 87, not so good.

 

If gas is really an issue then you should probably look into getting another vehicle. The IS also doesn't get very good mileage.

BTW, nothing but 91+ in mine since the day I bought it.