I run 93 only, my mods are chip, intake, pulstar plugs, resistorless leads, and a little tuning by me. I tried to run 87 before my mods and my little "Natascha" knocked and pinged oh! it was ungodly. There is a Circle K around the block from me. They have 100 Octane. Natascha runs soooo! nice. And the smell. MMMMM! racing fuel smells soooo! nice. Higher Octane fuel permits less carbon build up. The fuel burns hotter which burns the carbon. Lower octane does not. Once in a while you should add an octane booster to help clean out the carbon build up.
Well, too bad Natascha can't talk, otherwise she would be telling you that the 100 octane gas is burning up her catalytic converters. Higher octane gas is more resistant to combusting under pressure, but also burns a little slower unless it is compressed more, this is why your engine might also feel like it is running smoother. That wonderful smell you get is from unburned fuel going into your exhaust, continuing to burn, and cooking your catalytic converter. So in the end, the fuel in the cylinders will burn colder and the fuel in the exhaust will burn hotter.
To each his own I guess. When you realize that the stock intake sucks in air at 158f it becomes pretty obvious why bmw requires 91 octane or better for this engine. There is nothing special about a 10:1 CR engine using 87 octane. My 10.7:1 CR volvo has been for the last 260k miles. Fix the intake problem and you can use 87 octane at all temperatures.
Also please don't tell me in not going to hear ping or knock. I've seen the difference octane can make for this engine depending on air temperature, altitude and load.
158F intake temperatures aren't that bad at all. Most cars have much higher intake temperatures than you would probably expect. One cause is that heat from the cylinders transfers into the engine head, and from there to the metal intake runners and metal intake plenum. So all the intake air has to pass through heated metal tubing. This is also why putting an air temp sensor in your airbox won't give a very accurate reading of what is actually going into your cylinders.
The reason I run chevron premium is because its not like that shell trash. Chev gas is better because it doesnt sit in the tank for a week. Its cleaner and thus provides better explosions. Riddle me this. My buddy has an evo x and chipped it to 320hp at the wheels. Now should he run regular? No? Should he not use synthetic? No! I get what your saying cobra. If you want to save money like a goldstein run regular and drive like a grandma but I believe you should drive a non turbo base model volvo. I feel bad for anyone who uses crappy oil and crappy gas
Ps. His all aluminum engine is only 9:1 so certainly he doesnt need 92 or better. Hmmmm his air intake is in the middle of the hood. Must be cold! As cold as an sti's intercooler
-Chevron and Shell are both good gas companies to buy from. Any gas company with a Top Tier approval sells good gas. Here is a list you should look at:
http://www.toptiergas.com/retailers.html-If gas sits in a tank for a week, in simple, it will not change "how well it explodes". Gas is relatively stable when properly stored, but I still will agree with you that a gas station with lots of business is probably the better pick than one without much business.
-The reference to your friend's car is pretty irrelevant. I don't see how that his car has 320hp makes any effect on what kinda gas he uses. Give me the resources and I could manage 320hp with regular gasoline on an evo, it would just be a lot harder. Also the fact that is engine is aluminum makes not difference on the gas he uses. His compression ratio is also irrelevant to the gas he uses, especially since the car uses forced induction.
dirty meaning it sits in Arco's tank. Why do arco charge 15 cents less per gallon? Because there fuel sits for weeks and it becomes lower octane. I'm no chemist but this is easy to understand
Obviously, you are not a chemist. If fuel sits for a very long time in a tank it will degrade if anything, and not just become lower octane gas. You treat lower octane rating gas like if it is lesser quality of fuel. It is just as clean and refined as premium. The only difference is how easily it ignites.
Some of you guys should go work for BMW because it's obvious that you are way smarter that the top engineers that BMW hires to design there cars. It's amazing that these terribly designed cars still have such a following 17 years after they were first sold.
They state premium fuel because these are high compression engines with no knock sensors. While you may not always hear the detonations that does not mean it's not happening. You may not have engine failure in the next few thousand miles that does not mean your engine is not getting damaged. Even if you are not one to push the limit you probably still put the car under load enough to cause pinging, for instance going up a hill in a high gear.
If it's recommended to run premium that's what you should be running. If you want to save $200 a year sell your e30 and buy a Corolla, my wife's gets way better mileage than my e30 does and Toyota recommends regular fuel.
I would love to work for BMW and that is definitely a possibility with my career path.
BMW engineers are obviously very smart and did a very good job engineering the E30 3-series. Often though, they are criticized for including overly complex engineering at the expensive of long term reliability/maintenance/cost. Also of course, it takes time to figure out some mistakes and technology does change.
Another reason that 91 octane fuel is recommended is that back when the E30 was produced, gasoline quality was not nearly what it is compared today. The E30 was produced towards the end of the era when gasoline was being transitioned from leaded to unleaded.
I would guess that now, with current technology, you could run 89 octane or "Plus" gasoline and it would perform the same as 91 octane or "premium" back in the 80's
