1WILLY1

iTrader: (9)

ive used no less then 89 since i bought the car.

When I do go 91 or 93 it feels a bit better but im not sure if its all in my head.

The answer is if you have the money use premium as recomended, if not "I" think 89 is just fine.

TechGreek

iTrader: (4)

This to me, is wrong (sort of anyways) because people will not understand it. Yes, your motor will pull timing (to a certain extent) when knocking occurs but there are many more variables that happen for a car that is designed, from the factory, to run higher octane gas.

AIT, etc all play a role in the octane of gas (or pre-detonation), if it's hot outside and you run a lower grade gasoline that has more chance of pre-detonation you'll just enable it to do so, lowering power, gas mileage, and throttle response and potentially flooding your intake path and head with carbon (dumping fuel is a no-no).

EGT's can also go up when running a lower grade octane gas that's on the verge of detonating, but you won't hear anything, and when your EGR recycles hotter-than-normal gas/carbon guess what happens? Carbon Soot Yay!

You never, ever, ever want to depend on your car pulling timing as a sign of oops I should have put what octane gas my car was made for in there.

Both the 1UZ and 2JZ are high compression motors in N/A form, and are advanced ignition timing wise, from the factory.

If you're running an aftermarket ECU, have a EGT probe on each cylinder, and the ability modify all sensor (AIT, etc) then sure, you can toy with that, but until then is the $0.20 a gallon really worth the long term ability of your motor and components inside it?

And for the people that are worried about price, stop buying cigarettes once a week, or stop drinking that beer once a week. There are plenty of areas you could cut down to make sure your mode of transportation and fun stays on the road longer.

JDMJoe239

ive only run 93 so far. and i get my gas at sams club (roughly $.15 cheaper than anywhere else.)

Gate

91 for me, all the way. 92 SC4.

lemaylexus

My mechanic told me it doesn't make any difference. That said, I, like others, continue to put 93 exclusively in my tank because the manual suggests it.

BigBang

iTrader: (1)

I'm running 89... can't afford higher. so far no problems..

MDSC

iTrader: (3)

you'll spend roughly 4-6 bucks more if you fill up with premium over regular..is 5 dollars
really worth it to have this conversation over?

xspsi6

iTrader: (31)

It comes down to weather or not you car is vvti or not since vvti is aggressive in the timing map and high compression to boot and the worse it will do is get slightly less mpg's and have slightly less power however non vvti its just a waste of money.

If you believe your car gets better power on 93 the perhaps you should also invest in a tornado fuel saver or purchase some swamp land here in Florida.

TechGreek

iTrader: (4)

Says the guy who started a thread asking the same question a little bit back Do you honestly think the less power and worse gas mileage is just the ECU saying hey you can run cheaper gas? If so I've got a set of plastic rods that will decrease the rotating mass of your engine too!

Let me just specify since people seem to think I'm pointing at it will give you more power, it won't.

Your ECU will never advance your ignition timing for you if you use higher octane (say like the idiots that like to try and run race gas in a stock car). You will never make any MORE power than STOCK.

MDSC

iTrader: (3)

higher octane gas burns cooler= burns slower = better fuel economy=less power.

xspsi6

iTrader: (31)

Yes I did start a thread asking if the sc400 guys only were running premium still and I did hook up a Vi-pec knock amp to see if there was any audible detonation which only in the worst of conditions there was such as up a hill in od on a 100 degree day which was on 87 and on 89 there was 0 preignition so as I said anything more than 89 is a waste of money as it does not affect the engine opperation.

My thread was more to see if people were running 87 and for how long etc etc

TechGreek

iTrader: (4)

Which cylinders did you mic? Did you mic all eight? You can't just stick a knock sensor on the motor and expect it to be accurate.

How would anything MORE effect engine operation?

account2x

iTrader: (5)

That is likely because your ECU was using the same timing for 89 as 87.

xspsi6

iTrader: (31)

I had the knock amp in the stock knock sensor location and on full sensitive which will pick up even the slightest knock.

Anything more will cause unburnt fuel to allow the engine to run dirty and these cars run mega rich from the factory 12.4-12.8 afr under WOT which is just a factory failsafe built in to the ecu as if you were to build your own timing and afr map I would be willing to bet you could pick up 25-30 whp on the non vvti v8.

TechGreek

iTrader: (4)

What do you think happens when you run 87? Do you think the ECU just happily pulls timing and does nothing else? No, it will dump fuel to compensate for the increase in EGT, etc.

And no, the stock sensor is garbage, and the stock location is not exactly the best regardless. Unless you're monitoring all 8 cylinders you can never give any conclusive evidence as to what was going on, only a general blanket statement.