I’m awaiting a new car with a 10.5:1 compression ratio for which premium (91) fuel is recommended.
Will the octane sensor accommodate 87 octane fuel? Is the absence of detonation proof that it’s OK to use the lower octane?
Octane sensor? Is there such a device on the car?
Knock sensors that I am familiar with cause an instant and drastic retarding of ignition timing and possibly an increase in EGR flow. The loss of power would be dramatic, as would all aspect of performance. Any operation with low octane, other than constant cruise, would likely cause ‘knock’ and the resulting performance decline.
The owner’s manual has your answer. It might suggest that the car be run at all times on 91 octane but it will accept 87 octane has a last resort. Or it may advise you otherwise. Do whatever the manual recommends.
Pay no attention the those other guys laughing at you for shelling out the extra bucks for a performance engine but being too cheap to feed it properly. They probably do equally dumb things.
The owner’s manual will tell you (recommended or required) If required you are risking engine damage with the lower octane.
In either case you will get lower performance with lower octane with that car and you may get lower mileage. It’s up to you.
Don’t forget to get the skinny tires for even better fuel mileage. You want to have tires to match a detuned engine; why else detune it?!
Newsguy, we had this post before; people spend good money to buy premium cars needing premium fuel and they want the computer to accommodate lower octane gas. I only recommend this if you are stuck where premium is unavailable; then the computer will put you into the “limp home” reduced power mode. For best performance and maximum engine life put in what is recommended.
It’s a case by case basis. If pinging occurs then you should step up the octane.
Not using the recommended fuel octane does not automatically mean loss of power, performance, or engine damage.
91 octane is recommended for my Lincoln Mark and I’ve been using 87 forever. The car runs as well and fuel economy is the same as when 91 is used. Matter of fact, on numerous trips to Colorado I’ve used 85 and 86 with nary a hiccup, ping, or loss of anything. The car gets 27 MPG with 91 and gets 27 MPG with 85.
I pull my spark plugs at approx. 10k mile intervals and inspect the tips. Never a sign of anything abnormal after 135k miles. If there were, then I would have discontinued the practice long ago.
Do some net searching about octane rating and you’ll see that the U.S. octane rating is about 4 points or so lower than the European rating; on the same gas. A quote below:
Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the “regular” gasoline in the US and Canada, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as “regular”, equivalent to 90-91 US (R+M)/2, and even deliver 98 (RON) or 100 (RON).
JMHO to use as you see fit.
My wife’s 2006 Sienna 3.3 V6 has a 10.8:1 compression ratio. The manual “recommends” premium, but does not “require” it. We’ve been putting regular in it since day 1 and have had no driveability problems. No sign of ping or knock. On the other hand, neither of us drive it like a sports car. I may try a couple of tanks of premium to see if there is an increase in mpg, but haven’t got around to it yet.
Ed B.