i let my brother borrow my car for a couple weeks while i was away. he was using regular gas. i dont feel any knocks from the pistons like i expected. is it ok for me to keep using the regular gas or should i be using premium?

 

Its up to you. It is the ultimate saying of "you get what you pay for". Ive noticed that when I use premium gas, it lasts longer than when you use regular. Premium gas also helps the engine components last longer.

 

Just take it easy. One tank isn't going to hurt anything. Just top off with premium whenever you get the chance.

 

89 for me.. havent tried 87

 

The manual says premium only.......why use regular? Even when you open the gas tank it says premium fuel only. lol

 

This car won't run on 87. Literally, it will sputter and idle low. The VVTi high compression engine needs a certain amount of explosion in the chamber to burn properly and the engine flat out won't run on 87. It's like having water in the gas. Put premium back in it and it'll run twice as good.

 

I've always put premium 93 ocatane gas in my car since I bought it. It is up to you what you use, personally i say always use premium, but it's hard to convince some people of that. I get many people that call me crazy for buying premium gas, they say there is no difference between any of them except the color. Anyways I think differently, I still always put premium 93 octane gas in my car lol.

 

dont worry about, I always pump regular on my IS the manual says Premium is preferred but regular would do just as fine.

 

Don't listen to this guy.

People like that don't understand why Premium is required or recomended for the vehicles it's needing to be used in.
There's a few reasons why it's needed. Compression being the number 1 reason.

BUT wait you may think well thats a silly reason to use premium!?!?

I'm sure while you're driving the car and it's detonating you probably wouldn't know what detonation sounds like! Do you?

Aside from killing rings, pistons, and possibly blowing a head gasket go ahead and run 87 thru the car regularly and then call it a POS when the engine fails.

I can go into a few paragraph's long discussion on this but I wont.

To the OP go ahead and run most of it out and fill it with 93. Just take an easy on her while she still has 87 in the tank.

BTW I don't run 93 regularly in my 2.7l 2000 4Runner but when it starts to detonate and get sluggish I run a few tanks thru her and she's good for a good while and it doesn't require premium.

 

1 or 2 tanks wont hurt as the engine will adjust to the lower octane but always use premium for the above reasons

 

lol, I like this threat. Anyway, if they were the same, they would not be priced differently. I got my pre-owned IS and didnt know what kind of gas used before but since it's mine... premium is the only choice. I'd rather skip a breakfast to get the premium for my baby.. Love IS.
Note: I am very skinny.

 

93 all day.

 

Just put 93 in regardless of if u "think" it's a good idea to use regular voleduy is right they r not the same and the price difference between 87 and 93 is maybe 30 cents and that's pushing it. Take care of your car and it will take care of you. Enough said

 

Alright new idea, if you're a dumbazz enough to run cheap gas in your high compression engine then go for it..... it'll just blow up sooner and you can go back to the honda you started with since you can't afford to drive a Lexus.

These VVTI engines are very advanced over the "old chevy 350" and the high compression engine needs to burn as hot as possible in the chamber.

 

While I do agree that the use of premium gas is most definitely the way to go, as it is recommended, and it is what Toyota/Lexus tuned the ECU to run at, lower octane fuels burn hotter.

The octane rating of a fuel is it's resistance to detonation, ideally you want to run the lowest octane possible to get the best fuel economy and power. Lower octane gas actually contains more energy than higher octane. The lowest octane possible on the IS300 (in my opinion) is 91. If you run lower octane than this, the engine will retard timing, etc. and you will not be getting the most out of your engine.

Running 93 or 94, etc. isn't helping over 91. It may be better fuel for other reasons like the additives and/or quality, but having a higher octane rating alone does nothing to help you.

Jeff