ERAU-944

brrt: check the manual. it says 91 (euro) which works out to 87 US octane.

among other things, octane is a measure of how willing the fuel is to combust. the higher the octane the more you have to do to it (i.e. compression and temperature) to get it to combust properly. so unless you're jamming in more air (i.e. S and 951 cars) the extra octane is useless. brrt must be having some other issues (crappy fuel, fuel delivery problems, etc.) to have knocking with 89. i always used to use 93, but now i use 87, and if anything i've noticed an increase in performance, and no knocking.

brrt: use some techron in your next tank of 89 and see what happens, sounds like something isn't right somewhere, in all 3 of our cars 87 gets the job done no knocking.

-Michael-

Peckster

In Toronto Sunoco sells

- Ultra94 (94 Octane)
- Supreme (92 Octane)
- Plus (89.5 Octane)
- Regular (87 Octane)

The ultra is only one cent a liter more than the supreme, but there's a big jump from plus to supreme.

Bryan

Just wanted to second or third the idea of using the lowest, yes, lowest octane fuel your engine will tolerate without detonating.

The octane additive in gasoline does not burn. Therefore it is displacing combustible material. Less combustible material per unit of fuel means less power from the combustion process.

If you have a 16-valve car, your engine has these wonderful devices called knock sensors. They will prevent your engine from being damaged by detonation. Try out a tank or two of 89 or 87 octane and see how your car runs.

I was also made a tool of the oil companies and was buying 93 and 94 octane gas. I shudder to think how much I've spent on it over the years. I just put a tank of 89 in my S2 engined 944, and it's running like a top - it actually feel substantially peppier than it did on 93.

A friend of mine has a '92 Sentra SE-R and it's run on 87 octane since the day he bought it and it runs awesome and goes like stink.

As a general rule, your engine will ping at low rpms and high load. Like if you "lug" the engine. Low rpms give a larger time window for detonation to occur, and high load advances the igntion timing. So if your engine doesn't ping when pulling away from 1000 rpm in 2nd gear, it probably will be fine under all other conditions.

Bryan

jeeper31

ARe you actually saying the car runs better on 89 or 87? Haven't had the nerve to try anything less than 93.

ERAU-944

do it! i noticed a ~small~ improvement in power going from 93 to 87, i have had less hesitation problems when cold, and i have experienced NO knocking. my wallet is heavier though, time to reduce more weight

the 944 (8v) at least the lower compression models were made to run on 87, 91 in the fuel filler is the euro measurement which works out to 87 U.S.

-Michael-

jeeper31

That is good to know. I will try it. Looking forward to saving money now.

Z-man

Check the manual, and run with what it recommends. Our cars don't need race gas. They also don't need 94 octane. Higher octane gas won't hurt your engine, and lower octane won't either: that's why we have knock sensors: these devices will retard the timing/decrease detonation with running with a lower octane gas.

I usually run with 93 octane. A few times, I used 94, and noticed NO DIFFERENCE.

rsrdan: running a combo of 100 / 93 octane gas for the track is really just a waste of $$ with the S2, IMHO.

MPD47

When i filled my car up for the first time in Pennsylvania I had the choice of 87,89 and 95 so i went with the 95. When i got back to my house however I remembered that Sunoco dropped 94 for 93 in most places, and down to 91 in some places. I dont notice any difference between 95 and 93.

incessant

I for some reason am not able to add a link to the previous discussion, but it was early october titled "WHAT OCTANE GAS DO YOU USE?" with a voting poll. Resounding 91 as the answer.

Below is my post from that discussion.
----------------------------------
What the manual says

"Fuel Recommendation"


"944: Minimum octane rating is 95 RON (90 CLC or AKI rating on US pumps)."

"944 Turbo: Minimum octane rating is 95 RON (90 CLC or AKI rating on US pumps)."

"If unleaded premium fuel in not available, a built-in "knock control" on the 944 TURBO makes it possible for temporary use also to refuel with unleaded regular fuel with at least 91 RON (87 CLC or AKI)"

"Octane Ratings"

"Octane rating indicates a gasoline's ability to resist detonation. Therefore, buying the correct octane gas in important to prevent engine "knock" and
possible damage.
The 95 octane rating of your car is based on the research method. The CLC (U.S. Cost of Living Council octane rating) or AKI (antiknock index) usually displayed on U.S. Gasoline pumps is calculated as research octane number plus motor octane number, divided by 2, that is written as:

RON + MON
------------------
2
The CLC or AKI octance rating is usually lower than the RON rating:

95 RON equals..................90 CLC or AKI
91 RON equals..................87 CLC or AKI"


Bibliography:
"Porsche 944/944 Turbo owners manual" (Page 74).
Inside jacket dated 5/88.

For 89 models.


Rennlist Discussion Forums <index.php?s=> > Water Cooled Discussion Areas <forumdisplay.php?s=&forumid=49> > 924/931/944/951/968 Forum <forumdisplay.php?s=&forumid=70> > What Octane Gas do you use?

gleamingred944

Don't know about the US, but in Canada 'octane' is defined by the feds as being lower in summer than in winter, to reduce toxic evaporation. My manual says that a 944na only needs what works out to 87 Canadian octane. I find that 87 occasionally causes pinging, but rarely. In winter I use the maximum I can get here, 91, because of ease in starting. Even on the track, I have NEVER heard or experienced any problem with 91, winter or summer.

As far as I can tell, 944na's don't EVER need more han 91, and we probably could run perfectly with less.