Increased engine wear from 87 Octane

[harthamm]

I have a Nissan Maxima that calls for 91 octane. I have been using 87 with the same mileage and no knocking.
A friend of mine stated that the 87 will cause more engine wear. Is this truth or fallacy?

 

[d00df00d]

There are always occasional knocks that are small enough that you don't feel. So, theoretically, 87 octane could cause more engine wear.

Now, will it matter? Probably not.

Basically, unless you drive really hard, engine wear isn't a reason to go for higher octane.

 

[aquariuscsm]

I tried regular unleaded once in my Z31 turbo (that required premium) and it would barely run if you put your foot in it the least lil bit.

 

[mechtech2]

Increased wear is not the problem.
Loss of power and gas mileage is a potential problem.
If your knock sensor is going off and retarding your ignition timing, you are suffering power and MPG losses. Your computer will also relearn and lower the timing, if the sensor calls a knock too much.
It is almost always better to use the designated fuel. The price difference should make it a wash with MPG and power.

 

[Quest]

+1 to mechtech2 and dogfood's comments.

So...unless your computer failed to retard the timing a bit when sensing knocks, otherwise, running slightly lower octane shouldn't be too much of a problem (other than minor loss of power/output).

Afterall: with over 10.3:1 compression ratio, my 07 fit spec'ed for 87 octane rating and gets the best mileage out of it. I've already tried all kinds of gas and different octanes and get no perceivable benefits out of them. My computer keeps it well under control.

Q.

 

[lexus114]

Originally Posted By: Quest
+1 to mechtech2 and dogfood's comments.

So...unless your computer failed to retard the timing a bit when sensing knocks, otherwise, running slightly lower octane shouldn't be too much of a problem (other than minor loss of power/output).

Afterall: with over 10.3:1 compression ratio, my 07 fit spec'ed for 87 octane rating and gets the best mileage out of it. I've already tried all kinds of gas and different octanes and get no perceivable benefits out of them. My computer keeps it well under control.

Q.


Dude,you said dogfood...Eh,hahahaha,ehhahahaa.

 

[chevrofreak]

The problem is that a lot of cars don't have knock sensors. My 96 Crown Vic doesn't, so it has no idea hat it's detonating like mad on 85.5 octane. It even does it on 88.

 

[harthamm]

So bottom line, can I assume that if there is no knocking that my car's computer is adequately adjusting and that except for a mild decrease in horsepower there is no excessive wear?

 

[d00df00d]

As long as everything is in working order, yes.

 

[lexus114]

okay,but here is my question re;this.Is their going to be any other physical damage done to the motor say maybe long term by running it with the timing and fuel mixture altered?? I know years ago I would never have dreamed to run my motors on any timing other than peak. I.E just before a detonation.

 

[d00df00d]

Knock can cause wear directly by putting abnormal stresses on components.

An excessively rich mixture can cause wear indirectly: it generates excessive by-products and leaves unburned fuel around, which can get into the oil and compromise it.

 

[lexus114]

Originally Posted By: d00df00d
Knock can cause wear directly by putting abnormal stresses on components.

An excessively rich mixture can cause wear indirectly: it generates excessive by-products and leaves unburned fuel around, which can get into the oil and compromise it.


Plus the motor runs hotter on retard timing.

 

[BearZDefect]

harthamm, I didn't see the year of your Maxima, but the knock sensor on the fourth generation Maxima seems to last only about 60k miles. Its failure does not light the CEL, but if you read the codes you find it.

If the ECU detects a knock sensor failure then it is already using 'safe' timing for regular gasoline because it cannot detect knock. In this case you don't benefit from using premium gasoline.