It was in the paper last week that crude has gone down $2 a barrel. Prices should reflect that soon, but definately not before memorial day weekend. That would just be rediculous.

My understanding of how our cars adapt/function on lower octane gas is such that the ECU retards the timing to avoid pinging. This results in lower HP and torque. I'm not sure how this affects mileage. It's also my understanding that the higher octane gas burns more cleanly.

If you insist on using lower octane, ween her down slowly. Give the ECU time to compensate. Do a half fill with 89 (the other half being 93), then a full tank of 89, fill her half with 89 and ther other with 87, then try a whole tank of 87. If you don't notice any adverse effects, then you should be fine. Just remember, that HP rating that comes from the factory is based on high octane.

Another *trick you could try... Reset the ECU. If you drive with a lead foot, your ecu has learned this and compensates with an agressive fuel mapping. Take the negative battery cable off for 15 mins or so. Then put it back on, and drive like grandma I usually do the opposite, but that's becuase I want an aggressive mapping for the best performance. I reset the ECU then hit the highway under full acceleration and high speed for a few passes...

As to the effectiveness of either of these "tricks", I'm uncertain. If you search the fourms you will find others that have also said much the same thing you're reading here.

If you're wondering, I still run 93 (I even try to avoid 92), but I have been debating the idea of going cheap.

 

This will only work if when you have pinging, your detonation sensor actually picks it up which most of the time it won't.

If you run 89 and don't have pinging, you're probably OK. I run 89 in my sc400 but when I do, I don't drive it aggressively. No WOT runs.

You could retard timing by 4 degrees or so and run lower octane safely at the cost of some peak power, but you're gas mileage shouldn't suffer. Best thing would be to have your ECU reprogrammed for 87 fuel maps.

 

You're mechanic is an idiot. It's true most cars will retard the timing if you put lower octane gas than required......but only AFTER the ECU has detected detonation which means damage could already be occuring. Yes that's right, the only way the ECU can retard the timing for lower octane is IF IT DETECTS DETONATION. Even worse, detonation cannot be picked up by the sensor under most of the RPM range.

 

You need to adjust your timing. It is obviously far too advanced. Either that you have serious carbon deposits.

 

dont run low octane just go buy some cheaper gas like arco, costco or safeway gas. its cheap and you dont have to worry about running low octane

 

Hopefully everyone is already running off brand gas. Here in Northern California, all gas is refined at TOSCO, so it doesn't matter where you buy it. You get the same gas.

 

every brand??? even the mom and pop gases???

 

Yes. Every brand. The only difference is the detergent packages in some cases. In many cases, especially for the mom and pop places, the detergent package is exactly what what it was for one of the major brands as the same truck that just filled up major brand x came right across the street and filled up mom and pop.

 

i've been running 87octane ever since premium reached $1.50/gal

car = 92SC400 106k miles

no pinging, no knocking. My last dyno session I ran with 87oct and ran 214rwhp. I figure no point in going to dyno with super gas when I'm not going to fill her up with anything better anyways.

 

Knock sensors are placed at strategic locations to detect knocks at certain harmonic frequencies faster than human can. Try running engine with and without knock sensors under load cause that will tell you whether or not those sensors can detect detonation. Anyhow, some knocks are acceptable per Toyota instructions. Engines produce optimal power when they are on the verge of knocking, and the most reliable way to get to that point is advance the timing until knocks occur then back off a bit. The ECU constantly monitors knocks and store optimal timing values for future references.

 

Yes, but most pinging, even damaging detonation, cannot be picked up by the sensors in much of the RPM range. Knock sensors are there as a safety net in case you get bad gas or accidently put gas in that has a lower octane than your engine needs. Again, the only way the ECU retards timing due to lower octane gas is IF detonation is detected and if it is, the ECU will retard the timing to eliminate it. However, damage could already be occuring.

Some here report they can put 87 in their SC400s and others say they ping on anything less than 91. Each car will be different. The base timing is the biggest factors. Not all cars will be the same. Other factors are carbon deposits in the combustion chambers, temperature, humidity, etc.

 

depends on driving style, i baby my car and accel really slowly and on 87 it runs fine, but of course when i punch it to WOT or close it knocks, but not a lot before it is quiet again

 

strange... i beat the living daylights out of my car and it still runs great on 87oct.

i regularly redline it and no knock and no pinging.... **knock on wood**

 

well it depends, sometimes it knocks and sometimes it doesnt at WOT but the point is that 87 works

 

I've been using 87 on my SC3 and accelerate like crazy. I get no pings, great performance, and to a tank I get around 370 miles, all this with exhaust and custom BFI.