Premium vs Regular fuel?

[untrueparadox]

For me right now, I drive the i30 '98 with about 20k mileage on there. I received this car from my uncle as a gift and was never told to put in premium gas until someone at an Arco pump told me I'm using the wrong grade and would "damage" my engine. Both my uncle and I used 87 octane gas for 10 years on that same car without much problems, should I make the switch now or just go with the regular? I later read on the manual that premium is "recommended" so I take it that I can probably run regular? Bottom line is I'm trying to save money, whichever fuel takes me farther per $ will be the one I'm filling up with. The difference between 87 and 91 is 20c or more here in California and gas is about $3 where I live at the moment for 87.

[Nrw]

Yes you can run low grade fuel. The ECU will retard when it hears knock, knock sensor picks it up and sends the signal to the ECU. I personally only run premium, which is 93 around here. You get a bit better performance out of it and a bit better gas mileage, and less wear on the knock sensor obviously.
Modified by Nrw at 11:28 PM 8/2/2009

[asand1]

The ECU will RETARD TIMING when it "hears" detonation. Injecting more fuel would just foul the plug and cause a miss. low octane will result in retarded timing and less power. Premium should only cost another $2 per tank or so.

[untrueparadox]

for me its about a cup of coffee at starbucks but it stacks up. and i dont have a full time job or anything so i dont want to be spending unneeded cash. when i graduate in a year, ill probably be getting a new car so for me longevity isnt an issue.

so basically would the 20 cents per gallon or so be saving me money or losing money? i dont care about power because i dont race or floor the gas pedal at all.

also let me ask something, my car uses about 15 gallons at the pump every 1.5-2 weeks and i use it only to go to and from school on the weekdays with very little drive outside of that. its about a 10 mile round trip daily for 2 weeks is 200 miles? anything wrong when driving in the city and 15 gallons only last 200 miles?

[Nrw]

The ECU will RETARD TIMING when it "hears" detonation. Injecting more fuel would just foul the plug and cause a miss. low octane will result in retarded timing and less power. Premium should only cost another $2 per tank or so.

damnit. I need to stop giving advice when I've been out all night. Sorry about that and fixed my post so it's correct.

[jltibbs]

IMHO, there is no "vs." here. The long term problems caused by constant use of low octane fuel are not worth the risk. Knock sensors (though most do not replace them) are not cheap. You say you are planning on getting a newer car in a year anyways? Keep your I30 in good condition and use it for a secondary vehicle. Thus, take more care of it now for possible prolonged use.

[untrueparadox]

what specifically is knock? and does it have anything to do with like a jolt when i accelerate and the automatic shifts gear?

[Nrw]

what specifically is knock? and does it have anything to do with like a jolt when i accelerate and the automatic shifts gear?

pre-ignition of fuel

[untrueparadox]

so im guessing it doesnt have to do with the gear shifting? ill try to fill with 91 from now on.

[MinisterofDOOM]

what specifically is knock? and does it have anything to do with like a jolt when i accelerate and the automatic shifts gear?

Knock happens when the air/fuel mixture in the cylinder ignites BEFORE the spark plug has sparked due to heat from compression alone (like a diesel). Since when knock occurs, the detonation is occuring on the compression stroke instead of the ignition stroke as it's supposed to, it puts a lot more stress on the rotating mass of the engine in addition to cutting into power and making unpleasant noises.

But no, it doesn't have anything to do with gear shifting. Depending on what kind of "jolt" you're feeling, you may have a slipping transmission or it may be normal.

[untrueparadox]

the jolt is pretty bad. it feels like some one hit me on the back of the car. transmission..sounds like a lotta money. i know how it feels regularly when an automatic car shifts, its usually pretty smooth and such but when i press the gas a little too hard or sometimes when i accelerate from 0, itll get around 20mph and have that sudden impact feeling.

[97BlkMaximus]

Transmissions actually are not that bad if you can find a lower mile used one.I work at a used auto parts/recycled auto parts store and they run about $480 for a manual. However its the install/swap that your going to have to dish out the cash...If you know anyone in the biz you can get the whole thing done for less than $600.

BTW: I ONLY used premium in my Maxima.

[untrueparadox]

ya seems to me like everyone uses premium in their maxima. is it worth it to replace the transmission now or can i wait for a year and get a whole new car?

[jltibbs]

what specifically is knock?

[MinisterofDOOM]

ya seems to me like everyone uses premium in their maxima. is it worth it to replace the transmission now or can i wait for a year and get a whole new car?

Really hard to say. Transmission failures are hard to predict without seeing what's going on inside the trans itself. You might have a year or more, might have weeks. If it's slipping that bad, though, it probably is on the way out.

[untrueparadox]

^haha good one

so there isnt much of a way to check the transmission without taking it apart? i wouldnt say its too bad right now, most gears are very smooth, only the one that shifts at 20mph thats bothering me a bit. whats the consequence of having a broken transmission? anything dangerous i should be aware of?

i just got the car serviced at the dealer for one of those 180k milestones a year ago and they said everything was fine and that i can probably run the car for a couple more years with just regular maintainance.

[kc240guy]

It's a motor mount, not the transmission being bad. Mine does it. I need to replace it, but I spend too much time and money on my 240.