Your wagon requires 91 octane gas

wes wagon

Ha! I knew I could make you look! I was checking out the specs section of my factory shop manual for the '89 wagon the other day when I saw something I've never noticed before... it's says the required fuel octane is 91!!! This is right next to where it says the compression ratio is 9.2:1 (9.1:1 4wd).

Of course, the owner's manual suggests a mere 87 octane. Maybe this is why the shop manual I have is a "first edition" - because they needed a second edition to fix the typos in the first!

Mr G

Hmmm, what octane rating was used. 91 sounds wrong.

wes wagon

Mr G wrote:

Hmmm, what octane rating was used. 91 sounds wrong.

Yep, it does.

mtbikerTi

Was it listed as 91 Octane RON? In the US the AKI method (shown on the pump as (R+M)/2) is used to obtain octane. 91 RON is about the same as 87 AKI.

wes wagon

mtbikerTi wrote:

Was it listed as 91 Octane RON? In the US the AKI method (shown on the pump as (R+M)/2) is used to obtain octane. 91 RON is about the same as 87 AKI.

This coud be the answer...

I'll check to see if there was any more specification - there might be in the owner's manual, but in the service manual it definitely said 91, and I don't think it gave the method.
RON is "research octane" if I recall correctly, which is determined by actually burning the fuel in the lab. I'm not familiar with AKI, I'll have to do a little octane research of my own!

wes wagon

wes wagon wrote:

mtbikerTi wrote:

Was it listed as 91 Octane RON? In the US the AKI method (shown on the pump as (R+M)/2) is used to obtain octane. 91 RON is about the same as 87 AKI.

This coud be the answer...

I'll check to see if there was any more specification - there might be in the owner's manual, but in the service manual it definitely said 91, and I don't think it gave the method.
RON is "research octane" if I recall correctly, which is determined by actually burning the fuel in the lab. I'm not familiar with AKI, I'll have to do a little octane research of my own!

At the very least, the two manuals (owner vs. service) were using two different numbers, different methods? we'll see.

wes wagon

mtbikerTi wrote:

Was it listed as 91 Octane RON? In the US the AKI method (shown on the pump as (R+M)/2) is used to obtain octane. 91 RON is about the same as 87 AKI.

So yeah, mtbikerTi, the discrepancy comes from the 2 different methods. Here's what I found: the service manual specifies "91 research octane or higher" and the owner's manual specifies 86 or higher "pump octane". Upon reading up on gasoline specs inside the owner's manual (now if only had I done this before hastily starting this thread in the first place... sheesh!) it mentions that pump octane is the average of the research octane # and the "motor" octane # --> avg (or "pump octane") = (research+motor)/2 which is exactly what you stated in your post...