jdmSW20

iTrader: (12)

the same gas people ran in the 2IS, its the exact same motors in the 250/350

or you could just run the premium that it says to run

Jack1995

same here! I hand wash it every week and put only shell or chevron premium gas in it, unless I'm running on fume and have no choice to go to other gas station

FSPORTJC

Dealer told me that the iS250 FSport can run perfectly on 87 Octane Regular Gas and premium is not necessary.
I even asked the GM and he told me that the manager wasn't joking.. that its legit and it is confirmed with Lexus.

Ive always used 93.. I guess ill go in the middle and give 89 a shot and save a few cents which will eventually buy me a Chipotle Burrito Bowl.. Winning! lmao

yycdave

All modern engines can run on lower octane, but the engine detects the knocking and cuts back on power to run on that octane. It shouldn't hurt your engine but it will hurt your power.

keyframe13

Others might have a different experience but I put 89 for a month in my car and didn;t feel any hesitation and couldn;t tell the difference. Not even a drop in MPG, was even slightly better.

ISISGUY

And we all know, the dealership would never say something that wasn't true... lol

RedMica

Always 91 octane just because .

SonyHome

Where can you find 93 octane? I only see 91.

profet

Around here (Long Island, NY) Shell and Valero seem to have 93 octane.

Usually if the pump has 4 grades of gasoline (and not diesel) one will be 93 octane.

sc00b

i usually use 93
if i can find higher then I get that

ultran00b8

In Canada, although I can find 94 octane gas I choose Shell V Power (91 octane) because it is the only gas that doesn't have ethanol in it. Everything else has up to 10% and I can clearly see that V Power gives me better fuel economy.

Truly55

Shell V Power Nitro+ for me (UK 99 RON) and definitely got better mpg in my previous cars. Engines run sweeter too and are more eager on the throttle.

CobraGSF

iTrader: (2)

So on my way home I decided to fill up. Usually I put exon but decided to give the Sunoco gas station some business. Not really thinking I just pushed the gas all the way to the right when choosing which grade. While filling up I noticed 4 grades instead of 3 and realized I put 93 Octane gas rather than my normal 91. it was only 4 cents more per gallon so no big deal really . I paid $4.23/ gallon

Driving home I noticed a lot more pep and throttle response on just normal driving. What's the deal with this stuff? I've heard about it but never really knew what the true difference is, can anyone shed some light on this for me? I tried to Google it but couldn't find a definitive answer. Will the car benefit in the long run from using 93 all the time?

Also, what are your guys opinions on who has the best quality gasoline? Ive heard good things about BP, Shell and Sunoco. I know Sunoco is racing fuel so I cant imagine anything bad about it. Just trying to gain some knowledge here, Thanks guys.

KahnBB6

iTrader: (5)

93-94 octane is a good thing for any high performance car or any car designed to use premium. Manufacturers have to design ECU's to compensate for a range of octane ratings but cars that call for premium as per the manual usually have a fuel map designed for 93-94 octane gas. It comes down to the more expensive fuel being more capable of bringing the best performance your car can offer. It's more resistant to detonation and therefore your engine computer isn't pulling timing as much. With 91, 90, 89 or god forbid 87 your engine's power is severely limited by the computer because the lower the octane fuel the quicker it burns. This is fine for vehicles specifically designed to run on 87 or 89 100% of the time but not for a luxury car or high performance car requiring premium.

This is also why your manual states you CAN use very low octane fuel if you HAVE TO but only for as long as it takes to get to a gas station that sells higher grade fuel to top off with. Still, anything 91 or higher is considered "premium".

Perhaps it's apples to oranges but my SC was also tuned for 92 or 93 octane from the factory. It runs on the 91 we have in California just fine but power and ultimately some smidgen of fuel economy is sacrificed. There is a big difference between 91 octane and 93 or 94. I'd venture a guess that your IS doesn't need 94 octane but it should benefit from running 93 regularly. In Florida there is no 91 in most places, just 87, 89 and 93 so plenty of cars calling for "premium fuel only" run 93 all the time.

Beyond this, people with turbocharged cars need usually need the highest octane fuel that they can afford-- unless the manual says otherwise.

Someone else can better explain the physics of how different octane fuels burn in the combustion cycle, how high and low octane fuel and other byproducts are made from the same batch of crude oil and generally why high octane fuel is required for some engine designs but I hope this clarifies things a bit.

FinaLpeace

Honestly, the gas station's "premium" gas has its name to sell more expensive gas to customers with low performance cars who has no knowledge of octane requirements and such where they would come to believing that premium gas is better for their car. In other words the sign "premium" gas is there to misinform customers to using "better" gas for their cars when it is really only the octane that plays the role in the differences between regular and premium gas. Fortunately, higher octane would not have any affect on lower performance cars, that's why they can purposely mislead customers into buying it and would not have any damages to their engine. On the other hand, if you are driving a high performance car and do not use high octane gas to meet it's requirements then it would have negative effects on the engine.