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Will using a higher octane damage my engine?

edited November -1 in General Discussion
I have a 2007 Toyota Yaris with a little over 30,000 miles on it. Over the past year or so I've noticed some slight pinging when getting up to speed on the highway or climbing hills, but since last week the engine began pinging more frequently and a little more noticeable than before (maybe a bad batch of fuel?). So at my last fill up, I decided to put mid-grade (octane rating 89) instead of regular (87). This made the knocking virtually disappear. I don't mind using mid-grade permanently, but will using a higher octane fuel than what's recommended for my engine cause problems further down the road? Thanks for any help.
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Comments

  • edited November 2009
    No, using higher octane will absolutely never hurt your engine. But yours is the only situation where it is a good idea to go higher than the recommended octane. It never hurts anything but the wallet, but it's usually pointless.

    That said, if you've got pinging in a car that new, either you got bad fuel, or you've got a problem.
  • edited November 2009
    Thanks for the response. Some additional information:

    Before I put mid-grade in the tank, the pinging would occur between 1000-2000 RPMs under moderate or heavy load and it doesn't seem to matter if the engine is cold or running at normal temperature. Once the engine starts spinning closer to 2500-3000 RPMs, the knocking would go away, so I assume this is just the nature of an underpowered engine?

    I also think it has to do with the 4-speed transmission trying to stay in a higher gear for better fuel consumption despite the engine is practically lugging. I started forcing it into 2nd and 3rd gear to keep the engine spinning in the 2000 RPM range when I needed to go up a hill or get on the highway.

    With the mid-grade making the pinging stop completely, I hope the issue was just bad fuel.
  • edited November 2009
    Using higher octane fuel won't hurt you motor. I'm glad the pinging is gone. However I'd advise against lugging the motor, because that will hurt your motor.

    Shifting to a higher gear and keeping the rev's down is a good way to max your mpg, but with the small motor in your car you have to balance the mpg without lugging the motor. Go to the higher gear and keep the rev's low on downgrades or flat terrain, but not on hills.

    Your motor takes higher rpm to make sufficient torque to cope with inclines. So on hills let it rev to about 3,200 rpm then shift to a lower gear and keep the rev's at 2,500 or higher as long as you are going up hill. My guess is you'll use less fuel going uphill at 3,000 than lugging up the same hill at 2,000. At the higher rpm your motor will he happier and last longer. Lugging the motor puts a lot of stress on the bearings, and crankshaft.

    Going up hill at a few more rpms won't do much damage to your mpg, but will avoid damage to your motor.
  • edited November 2009
    Out of curiosity, what grade of fuel does Toyota recommend in your owner's manual? I suspect it's probably regular (87) but just checking.
  • edited November 2009
    Toyota recommends 87 octane in the Yaris, if it has four speeds, it has an automatic transmission. The manuals are 5 speed.

    Make sure the EGR is working normally. When the EGR valve fails in a closed position, you get detonation at cruise and lower mpg.
  • edited November 2009
    Is this engine supposed to have its spark plugs changed at 30k miles?
    Is the Powertrain Warranty still in effect?

    If a car this new is pinging, unless there is truly a "bad fuel" issue, that situation indicates either a need for maintenance or a need for repair. Check the Toyota Maintenance Schedule to see when it calls for spark plug replacement.

    If the plugs are not due for replacement at 30k, if the pinging continues, and if the Powertrain Warranty is still in effect, then you should take it to Toyota for FREE repair before the situation causes valve and piston damage that you have to pay for after the warranty expires.

    Right now, you are putting Band-Aids on what could be arterial bleeding, so to speak.
  • edited November 2009
    Everyone here is making the assumption that car engines are built with the precision of a Swiss watch..They are not..Your engine, for whatever reason, could have it's compression at the upper limit or the ignition timing control/knock sensor is a little out of whack. Changing the knock sensor MIGHT help, or simply changing BRANDS of gasoline (try a "top tier" brand like Shell or Conoco/Phillips) might cure the problem and save you some money. I disagree with the EGR reference. That valve is closed and not in the picture during any acceleration period..A rip to the dealer to check the timing and knock sensor might be in order..
  • edited November 2009
    In addition to the others' good advice, this is one situation where I'd run a full dose of a fuel system cleaner through it (like Techron, read the lable so see how much). I'd also try Shell gas for a while to see if it cleans out some deposits. Cheap, may help.
  • edited November 2009
    That's funny, I've had EGR problems cause a knock at light acceleration before.
  • edited November 2009
    That's what I've been doing. It's an automatic transmission (I think you're under the impression its a manual), so when I have it in drive the transmission likes to stay in high gear and the torque converter coupled even when I'm trying to go uphill or get up to speed. For instance, I could be accelerating at 30-35 mph uphill and instead downshifting into 3rd gear, the transmission stays in 4th and chugs along at 1000 RPMs, thus the pinging occurs.

    I'm not a leadfoot so I'm trying not to floor the accelerator...instead, I'll change the gear selector to 3rd or 2nd gear to keep the engine spinning faster for the extra torque and smoother acceleration (which stops the pinging).
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