gasoline! - Toyota Nation Forum : Toyota Car and Truck Forums

ebolabar · 09-07-2007, 02:15 PM

hey guys,
Is premium fuel reccommended or REQUIRED for mk3's? I would like to keep using regular gas but not if it's going to hurt my car

jon_570 · 09-07-2007, 02:24 PM

i think it says 87 is fine but it recommends using at least 89...i use 89.. and ill use it till i start modding

CRE · 09-07-2007, 02:58 PM

Depends entirely on how you drive, climate (humidity and air temp), altitude and if the engine's running stock or not. For the average driver I recommend using the lowest grade you can without the car feeling hesitant or like it's missing at higher RPM.

willtotheumm · 09-07-2007, 06:51 PM

103 octane and nothing less!!!!

well...actually my Supra doesnt even run at the moment so... yeah hahah. 0 octane FTW!

shaeff · 09-07-2007, 09:19 PM

Quote:

Originally Posted by willtotheumm

103 octane and nothing less!!!!

well...actually my Supra doesnt even run at the moment so... yeah hahah. 0 octane FTW!

i hope your car is very modified, otherwise you'll be slower than a car with similar modifications.

so many people think that a higher octane rating will net you more power, which is entirely untrue.

CRE is right on. use the lowest octane possible without pinging. (or feeling a noticable decrease in power due to the timing being pulled)

93 octane fuel burns SLOWER than 87 octane. you want to use high octane fuel with a high compression motor, whether it be a high static CR, supercharged, or turbocharged.

now, just because you're turbocharged doesn't mean that you automatically need 93 octane. if you're stock, you could probably get away with 87, but might experience pinging on a hot day. a safer bet would be 89. i ran 89 on my car for quite a while at stock boost levels.

once i started running 15psi, i went to 93 octane. so many people overlook octane ratings, but there's power to be made simply in the fuel you use. take advantage of the cheap fuel, and more power! especially if you have a stock motor!

-shaeff

CRE · 09-07-2007, 09:38 PM

Thanks for posting that Shaeff... i get so sick of trying to fight all the bad info out there sometimes and I really didn't want to cover that one again.

shaeff · 09-07-2007, 09:46 PM

no problem, man.

-shaeff

jon_570 · 09-08-2007, 12:43 AM

the fuel rating is really just the resistance the gas has to detonation.

CRE · 09-08-2007, 01:44 AM

Or how long it takes to burn.... It's not just a matter of detonation. Running too high of an octane can result in higher EGT, O2 sensor damage, power loss and in some extreme cases burnt valves.

jon_570 · 09-08-2007, 03:21 AM

^^ it realy cant damage the o2 sensor unless you got some WAY SHITTY fuel... or youre running SUPER SUPER rich..

even then. the o2 sensor wont get hurt from what octane you use.

CRE · 09-08-2007, 03:52 AM

Bud, I've got an O2 sensor that's going to cost me $100 to replace because the stock location is simply too hot at stock timing.... take my word on this one. I didn't say it was common, but it does happen. The only reason I didn't have HUGE problems is thanks to a massive timing advance which brings down my EGTs greatly.

The reason for the increase in EGTs is quite obvious and O2 sensors have a limited operational temperature range and lifespan (a factor of which being the temperature range they're typically exposed to).

TcmaBoy · 09-08-2007, 11:41 AM

Quote:

Originally Posted by CRE

Bud, I've got an O2 sensor that's going to cost me $100 to replace because the stock location is simply too hot at stock timing.... take my word on this one. I didn't say it was common, but it does happen. The only reason I didn't have HUGE problems is thanks to a massive timing advance which brings down my EGTs greatly.

The reason for the increase in EGTs is quite obvious and O2 sensors have a limited operational temperature range and lifespan (a factor of which being the temperature range they're typically exposed to).

It sounds like you have a lean out problem.

CRE · 09-08-2007, 03:02 PM

Quote:

Originally Posted by TcmaBoy

It sounds like you have a lean out problem.

Nope.

Regardless, you guys are missing the point. Even one grade of gas can mean a big difference in your EGT. The gas was still burning that much closer to the time that the valves opened and as little as a couple ns can mean enough of a temperature increase at high RPM to shorten the service life of certain components drastically. The relationship is much like the one between EGT and ignition advance.

I wasn't trying to say that it was extremely common, happens often, will happen from going up just one grade higher than you need, or that it would result in instant death. My statement did come off as a bit final but I was just trying to make a point.

As for my own issue, that occured for a couple different reasons.