Why Premium Fuel?

[Riley P]

Just a quick question to anyone with technical knowledge.

Now that cars have direct injection for gasoline, what is the point of needing a higher octane fuel? Higher octane has no more energy in it than lower octane fuel (ignoring ethanol), and the need for it to resist detonation is eliminated because the fuel is injected when it needs to be ignited as opposed to just sitting in the cylinder waiting for the spark plug to fire, which it still does...... Hmmmm.

 

[buckhorn76]

burns cooler.

 

[Keith Tedford]

Early injectors had a problem with the corrosive nature of ethanol. lawnmowers, chainsaws, outboard motors etc had a real problem with ethanol destroying fuel lines and susceptible metals. Ethanol doesn't give quite the gas mileage. I just use premium unleaded in everything to avoid any potential problems. With our '05 the manual recommends premium fuel but it not required.

 

[CCO]

Apparently we don't need to burn super but if we do we get slightly more power.
It used to be that detonation was the issue with lower octane but now with spark/timing control that's no longer an issue.

I personally think it burns cooler, at Doug says, as well as burns cleaner.

I wouldn't be afraid to burn regular in a pinch but I'd be listening a little closer for any pinging just in case.

C.

 

[buckhorn76]

cooler burning means less chance of hot spots developing in the chamber which in turn can cause pre ignition. one of the coolest burning fuels believe it or not is nitromethane.

 

[XFIRE82]

....my bulk dealer told me that regular only has a shelf life of 60 days, premium will last a long time and doesn't have the water in it ( not sure how much longer ). I only use premium in everything. Years ago I had to put some regular in cause they were out of premium, so I tried a tank in my 200 cube industrial ford 6 cyl. Full throttle in the field it burned the 20 gal tank in 6.5 hours. On premium it runs almost 9 hours on a tank.....cheaper to burn premium than regular !! Premium doesn't go stale and milky in the tank over winter in something that sits 6 months.
Now the new engines of today are designed to work on regular mostly I guess so that is what they need. The guy who owns the 70 Vette I'm working on just got rid of his Buick Enclave. He also just used premium like me in everything. He had a problem with this thing not starting after -10, it just won't fire, and can't plug it in cause the computer won't let it untill it hits -18. Totally disgusted with it, but he was told to try regular gas, so he did. Well it cured the problem, it starts and even runs nicer he said. How can gas make such a difference ? How dumb has technology become that a computer knows what is in the tank ? Hard to believe but it is true.
This 70 I have here had gas in the tank from 1979. If I didn't see it I wouldn't believe it but the tank is clean, fuel was clear and no stink. It would probably burn too but it was taken out and I put fresh premium in before I fired up the 454. I miss the good old red gas !!!!