Gasoline Suggestion

[Ranger X]

The manual says 87 AKI and 91 RON. The car is a '90 BMW 525i. Does this car need 87 octane or 91 octane?

 

[notfred]

If it knocks with 87 in it, switch to 91.

 

[Ranger X]

How can you tell if it knocks? Does it make an obvious noise?

 

[Electric Amish]

Just suck it up and splurge for that extra $1 per tank and get 91. 😉

amish

 

[notfred]

<< Just suck it up and splurge for that extra $1 per tank and get 91. 😉

amish >>



Probably the best idea 🙂


Yes, knocking is a very obvious noise.

 

[Peetoeng]

<< How can you tell if it knocks? Does it make an obvious noise? >>



Typically you can hear it on a climb especially when you are on higher gear. You'd hear a periodic knocking sound and feel less power from car. If you are an aggressive driver, defintely get the 91.

 

[b0mbrman]

Depends how you drive...

 

[etech]

The number posted on the pump is aki or (R+M)/2. You should not need a higher octane than is listed in your manual.

chevron.com/

Octane number is a measure of the antiknock quality of gasoline ? the ability of the gasoline to resist knocking when it is burned in an engine. There are two laboratory tests to measure octane which are run in a single-cylinder engine operated under different conditions: Research octane number (RON) and Motor octane number (MON). The octane number posted on gasoline dispensers in service stations is the antiknock index (AKI) ? the average of RON and MON [(RON + MON)/2, usually abbreviated (R + M)/2]. The AKI was chosen as the posted value because experience showed it to be the best indicator of the antiknock performance of gasoline in the majority of vehicles.

For starters, use a gasoline with the AKI recommended by your owner's manual. (The owner's manuals for some older foreign cars recommend an RON value instead of an AKI value. A rule of thumb is that the RON of a gasoline equals the AKI + 5.) Using gasoline with an antiknock rating higher than that required to prevent knock will not improve a vehicle's performance, including its power, unless the vehicle is equipped with a knock sensor (see below).


In other words, 87 octane should be fine for you car.