RussRPJ

Related to JoshB's post, what octane would be best for a 85.5 944na with 125k miles? Owner's manual printed back in early 1985 says anything better than 87 is fine, but the guy I bought the car from a couple of months ago said don't use anything but premium (around here the highest premium is 91). Sure, the car theoretically should perform better with the higher octane, but just how much of a difference would I expect running the mid-level 89? Car engine is stock, no mods. Reason I ask is I have a problem of a raw-gas smell in the garage when I put the car up for the night. Is there a relationship between too-high an octane and incomplete combustion? Just thinking out loud.........

Jerad

I think 89 is fine for these cars, but I run premium just to be safe. My friend had an '83 and fed it 87 with had no problems and just sold it with over 200k on the engine.

As for the fuel smell, you might have a leaky injector. This causes fuel to run down the cylinder and in the oil. Pull the dipstick and smell the oil for fuel smell.

snappy

The specs only require 89, if you want to keep it clean, Then do the 4 -1 ration. For every 4 tanks of 89 oct. Fillup one tank of Premium. The higher octain will remove mos tof the gunk left behind by the "oiler" 89 octain..

RussRPJ

Oil smells OK. Don't think that's it. Is 89 that much different, is "oilier" than 91? Anybody ever use any of the redline injector and valve cleaners? Seems like that would work better to clean out a gunky system that just a 2 octane increase.

Jerad

Don't know about the oilier part, I have never heard of that.

As far as fuel system cleaners, Chevron Techron is the Porsche Approved one.

cherokee

Lets clear a few things up. The difference in the ratings of fuel is the flash point of the air/fuel mix. Unless your car is pinging during accl. run the 87 you will not hurt a thing. There are several things that could cause you to need to a run higher octane (carbon buildup/hot spots) these will cause pre-ignition or detonation and that will put holes in pistons. "The higher octain will remove mos tof the gunk left behind by the "oiler" 89 octain.." This statement is bunk.

The only thing that you will get out of higher octane is you will be-able to advance your timing a-little...thats about it. I would reccomend sticking with the MFG. reccomendations.

cherokee

The gas smell could be anything from simple and painless to very bad and car killing. You could have emissions problems charcoal canister to gas cap, on the bad side you could have a leak at injector/fuel rail (very bad big fire)your car is an 85 and just a little rubber o-ring seals the gas in. I doubt that you are having an over rich problem (gassy smelling oil) other problems usually come along with this.

RussRPJ

OK, thanks. The octane thing is likely a matter of debate. There are those that say they get smoother acceleration and better mpg using the higher octane. Personally, I never noticed much difference in other vehicles. The fellow I bought it from also told me that premium 91 is all he ever burned in it, but I still think that was just his choice. Think I'll drop to 89 and try that a while.

Gas smell is worst when I crank up in the AM to go to work. The car chugs and sputters for about a minute, idle bouncing around from 300 to 800 rpm. Really stinks during that period. Finally, it kicks-in and goes up to 1100 rpm and you're ready to drive off (it will just die if you drive off before that). I have looked at the tailpipe while it was "warming up" and saw not only black smoke puffs, but small liquid droplets being blown out onto the concrete. Its most likely just water. At least, I hope that's all it is! Could also be unburned fuel (possible source of the smell) and that worries me.

cherokee

If it is just a cold start problem it could be the cold start injector. I would doubt that the moisture you see out the tail pipe is fuel...you are most likely correct in it is water. If it is SO rich the liquid fuel is comming out the back I doubt it would run as you say it does. I would check around the fuel rail area for your problem. If you have never had the injectors PULLED and cleaned then you may be looking at those little rubber O-rings I was talking about.

brianh

ran my '89 944 n/a on 89 for years with ne'r a ping to be had.

brianh
'94 968

Devia

I use the Chevron Tech valve cleaner on my boyfriend's Eclipse, every other tank.

On my '85 944, I would alternate between 89 & 91 octane, depending on what I was going to do with her.

Also, I would suggest to NEVER use Arco gas; the additives they add have always seem to me to prematurely burn out the spark plugs. Just IMHO. I could be wrong, but I haven't had any problems with any car, since I quit using the cheapy stuff.

- Julie

Luis de Prat

I ran U.S. premium gasoline in my '83 for 8 straight years until last year, when a thread on Rennlist convinced me that I was just pouring my money down the drain and I switched to 87.

Didn't notice any change in how the car runs. It now has 202K miles on the original engine. I say drop to 89 or even 87 and if the car doesn't ping, why bother with the higher octane?

In Europe I do put Euro 98 in the 951 (must be something like U.S. 93 octane) simply because of the turbo engine, but I'm sure Euro 95 (probably like U.S. 91) would be enough.

YMMV

Boy Racer

Your problem could well be a sicky airflow meter. I had a similar problem only much worse that happened one day. After hours of diagnosing, a tap on the airflow meter brought things to normal again, but I do get that same roughness now occasionally for a while after I first start.

RussRPJ

I think its due for a bow to stern tuneup. Don't think its ever been properly done as far as I can tell. Got a leaky water pump now. What's next? BTW, here's an interesting one. One of the mechs at the local Pep Boys store/garage told me that you have to burn only Chevron gas in order for the Chevron Techron fuel system/injector liquid cleaner to do its job. If you burn anything else, its like you've neutralized the whole process and no effect. New one to me. Ever heard that before?