bureau13

My manual ('86) suggests to not use "gasahol" if you can avoid it, but if you have to it's OK unless (insert list of gas-related symptoms) happen...

hwyengr

What's unfortunate is that premium is now going for a real price premium in the Midwest. Usually 40-50 cents higher, but occasionally 60 cents at some stations in Chicago. But if there's a bright side over the west coast, it's 93 octane instead of 91.

safulop

Right, the list of symptoms! I almost forgot. My 944 exhibited nearly all of them unless running with premium.

Chalkboss

I run 91 here in California, and almost always Chevron. I recently looked at the backside of my valves during an intake refresh and they looked new (at 90K miles), so I think I do like the Techron they use. After reading a bunch of old threads on here regarding octane I tried some 89 and noticed no difference, but decided to just keep using the 91. I think the larger issue here in CA is the ethanol.
I also second Dr Bob's observations- I regularly travel from CA to OR and notice a nice improvement in mpg going north.

19psi

Wrong again.

Right out of a 944 owner's manual:

Unbelievable how many of these evil ethanol threads start because people think methanol is the same thing as ethanol:

GregBBRD

You need to run 91 octane in your S4 to get the best performance from it. The knock sensors will manage if you run a tank of 87 octane, but you will be "missing" at least 5 degrees of timing, on average.

Here, in sunny Kalifornia, when the price of fuel hit $3.00 per gallon, the price difference between the different grades of fuel was (at almost every station) $.10 per gallon....so the cost difference between a tank of 87 and a tank of 91 was about the cost of a cup of home brewed coffee.

It will be interesting to see of the delta between the different grades changes, as the price of fuel drops. Keep in mind, that we are still paying $2.39 per gallon for 87 octane.....while the rest of the nation is way lower than that.

They charge for the sunshine.....

uncre8tv

I am not a fuel scientist, but I have followed stuff like this from a long time back.

- ethanol, by itself, is an octane booster (it's ~110 when pure)
- therefore, octane rating w/ ethanol means you're getting LOWER octane gas that's then boosted back up (% wise) with the ethanol blend.
- ethanol will separate from gas and is heavier! this means you can be getting a "bad blend" or a "good blend" (depending on where the pump draws from the tank) if the fuel station doesn't sell a lot of your grade (esp concerning to us what run premium and live in the boonies!)

Anecdotally, I've only put 91 in my S4 since I got it, and it's got a multitude of issues, but I'm rarely seeing 16mpg. Usually in the 15's. I don't blame this on the fuel though, still a lot of reconditioning/maintenance to do. And I rarely drive it at a civil pace ... (apologies to someone on here whose pic I stole for fuelly.. btw)
http://www.fuelly.com/car/porsche/92...ncre8tv/334516

Tim Noce

Very true, I live in downtown chi and have to drive 30-40mins if I want even a decent price. Luckily there is Costco...

dr bob

Getting further off topic, but... The early justifications for oxygenated fuel in California used some interesting but ultimately bogus science. MTBE was touted as the saviour to the atmosphere, based on calculations that showed significant improvements on a per-pound-of-fuel basis. They neglected to share that the total energy available was also proportionally less, so we ended up paying for more pounds of fuel to go the same distance, ultimately spewing the same number of tailpipe tons per mile driven. Ethanol is slightly, but not much better in the 'available energy' department. It's benefits are much more closely tied to corn subsidies than to tailpipe emission reductions on a per-mile-driven basis. Benefits show up only when cylinder pressures are really high, enough to take better advantage of the improvements in anti-knock characteristics with better engine management.

terry gt

In Canada , at least in BC we have 87 89 91 and 94 , the 94 has no additives

safulop

Just to clarify, I had been thinking of an older user manual; the 88 S4 manual says to use Premium fuel only, so Porsche's recommendation is pretty clear. That's what I'll keep doing. I do notice the mileage goes up and down like crazy with different batches of gas, time of year etc.

The Forgotten On

Winter blend gas gives you less mpg's. That is also why it is cheaper than other seasons.

But the S4 should use premium only as it is a high compression engine Same with all of the euros and the S3. The only ones that can get away with normal gas are 80-84 L-jet cars.

SteveG

How many people don't have an Owner's Manual or haven't read it? Amazing.
Like the New Visitor thread, it has a lot of information in it very useful to the, ah, O w n e r.

dr bob

Funny thing...

Before I finalized purchase of my car, my first 928 purchase was a brand new Owner's Manual from Mark via one of my brothers. It was a pretty good pre-purchase read. Very early in the maiden voyage from Denver to L.A., I had to stop and reread the manual to clarify the cruise control operation.

The original Owner's Manual is still in its original sealed plastic bag. I carry the now-fingerprinted one I got from Mark back in 1997.

Jetdriver69

Back in 87, I put half premium leaded and half 110 octane aviation gasoline into a gray marketed 79. I ran like a scalded cat, but avgas was and still is very expensive.