What is the elevation where you live? It affects the octane requirement... the higher up you are, the less you need. That's why you don't see a lot of stations with 93 in Denver

 

94 Ultra...

It's such a good feeling when you go to the gas station and use the VIP pump for sports cars.

 

Figure it this way, premium is roughly .20 more than regular which is about 3 extra dollars a full tank. I would say 3.00 is cheap insurance in avoiding pinging and possibly damaging your engine.

 

My dad (who's been around cars for decades) and others have told me it's unnecessary to run 93 in my car.......I've been putting 87 in it since I've had it (about 3 months now) and I've had no problems.

My dad's '70 Buick Gran Sport Stage 1 needs 93 otherwise it'll ping........but I've heard it's unneeded to run premium in a '94 Z28 with no mods.

 

Like what GT KILLER said, if you don't have any mods, it's probably fine to run 87, i run 87 and have been fine, but now my tranny gave out so i can't drive. But the manual does call for 91 or better octane. And as someone else pointed out, 3 dollars more a tank is safe insurance, get it and you're car will last longer and save money in repairs in the long run.

 

Read your Owner's Manual. Clearly states high octane fuel is required, that you can run lower octane fuel, but could suffer from performance loss. When the PCM senses knock from low octane fuel, it retards the timing. That can cause a significant loss of HP. Won't damage the engine in any way, but it isn't giving you the performance its capable of.

As I recall the Owner's Manual recommend at least 91 octane to avoid performance loss. When air temperatures are high, the octane requirement increases. So running 87 in the summer (depending on where you live) will cost you lost HP.

You can verify the proper octane level for your car by putting a scanner on it and looking for knock retard. If you have any, you're losing performance.

 

So it's just costing performance? It's not in ANY way damaging anything temporarily or permanently?

 

I run 92 octane only if I absolutely have to..I stick to 93

 

Hmmmmm, I wanna try some 93 next time I fill up, just to see if I notice any performance gains. Is it ok if I wait until my tank is like at 1/4, then put in 93 over the 87 I just filled it with on Sunday? Basically is it ok to mix a whole tank of 93 with a little left of 87 already in there?

 

Depends on how poor the quality of the fuel is. The PCM can pull up to (roughly) 15-degrees of timing to protect the engine. Normally, when this happens, you will not hear the "knock".... the knock sensor hears it before you do and retards the timing.

However if your fuel quality is poor enough, more than the PCM can compensate for, and you can actually hear the knock, you are at the point where damage can happen.

 

yeah, its fine

 

OK, I don't remember hearing any knocks.

 

So have you ever ran 93 in your Geo??

I get much more mpg with the 93, so I will stay 93 period. I get 3-4mpg more(city) EVERYTIME.

I went from 200miles on 7-8 gallons to 230 on 7-8 gallons. I check mileage EVERYTIME I fill up...I've had this beater car for 3 years for 1.5 years I ran regular and the last 1.5 years I've ran premium, so it's not just a one time thing.

I'm just stating the facts....from experiance.

 

OH and the only reason I run 93octane is for the mileage, not because 87-89 isn't efficient.

 

You WON'T hear it because the knock sensor is much more sensitive than your ears The only way to know for sure is to scan the car and check for knock retard.

The problem with these knock systems is that they are reactive, not proactive. They don't prevent knock, they lessen it. If you're running low octane, it has to ping before the timing is pulled out. The PCM will slowly add timing until it pings again, and repeat. It will do this unless it's so bad that it goes into low octance mode.

Even with the knock retard, it's not good for the engine because it WILL knock. You also have to consider the loss of effeciency. You will burn more gas as the engine is constantly altering the timing. In the end you have less power, more abuse to the engine, and you lose fuel economy (which negates some of the money saved on fuel).

I will never understand how someone can spend thousands on a car, thousands on insurance, tires, oil, etc., etc. and then avoid the extra $0.20 for gas Buy an economy car if that's what you're after!