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Message started by shawn on Dec 3rd, 2014 at 7:07am

Title: Fuel type/grade for porsche 944?
Post by shawn on Dec 3rd, 2014 at 7:07am
Does anyone know if a 1983 porsche 944 uses regular (87 octane) or premium (93 or higher octane)?

Title: Re: Fuel type/grade for porsche 944?
Post by Zundfolge on Dec 3rd, 2014 at 7:19am
Welcome to the forum! Shoot your questions, and pay with pictures :P

See if you can find an owner's manual online, there you'll find that kind of information. Old school manual expecting old school users, they describe how to change fluids etc. - unthinkable today!

Note that US cars are rated differently than rest-of-the-world (RoW) cars. Here's the US manual:

"Fuel Recommendation
Your Porsche is equipped with a catalytic converter and must use UNLEADED FUEL ONLY.

944: Minimum octane rating is 91 RON (87 CLC or AKI rating on US fuel pumps).

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

Federal law prohibits use of leaded fuel in this vehicle.
[...]"

Followed by a definition/conversion of different "octane" numbers.

RoW cars have a higher compression and are supposed to run on 98 "octane" - note that the definition of "octane" may differ, and what "regular" means, too.

Title: Re: Fuel type/grade for porsche 944?
Post by marty944 on Dec 3rd, 2014 at 1:57pm
Now that octane ratings are posted, here is an additional comment: avoid ethanol. avoid it in your lawnmower as well as your classic cars. the brand is not as important as the octane and the purity. I have one local provider that has a mid grade that is sold for about 5% more than the ethanol low price leader. I get an additional 10% range from this fuel over ethanol, so the savings is direct. this does not count the savings to the indirect engine maintenance. it is not necessary to pay for premium.
I would also recommend at least an annual fuel additive course. I prefer Lucas, some prefer Chevron, some like Sea Foam,  but whichever brand you choose be sure to keep that fuel line clean. it is much easier to keep the injectors clean than to repair.
I also suggest an occasional treatment, if not continual, of Marvel Mystery Oil in the fuel. I have found it at wal mart in a large jug.

Title: Re: Fuel type/grade for porsche 944?
Post by Greg_P on Dec 4th, 2014 at 8:51pm
Good information above.

In my '84 NA I always use unleaded regular.  Runs great.

Greg

Title: Re: Fuel type/grade for porsche 944?
Post by pfarah77 on Dec 4th, 2014 at 11:11pm
I typically use Shell, Mobile 93, or Sunoco 94 octane whenever possible.

Title: Re: Fuel type/grade for porsche 944?
Post by Dave W on Dec 5th, 2014 at 11:00pm

pfarah77 wrote on Dec 4th, 2014 at 11:11pm:
I typically use Shell, Mobile 93, or Sunoco 94 octane whenever possible.


You're just wasting money unless you have a turbo.  The NA is spec'ed to use 87 octane (US rating).

Title: Re: Fuel type/grade for porsche 944?
Post by Joe Sharp on Dec 6th, 2014 at 2:22am
I also use 93, but only because the station in my town that does not have ethanol ,only has ethanol free gas in 93 octane.

when gassing up somewhere else I only get the 89.

Title: Re: Fuel type/grade for porsche 944?
Post by pfarah77 on Dec 6th, 2014 at 3:10am
Dave,

I found the car actually is more responsive and gets better gas mileage.

Title: Re: Fuel type/grade for porsche 944?
Post by porschecidal_maniac on Dec 6th, 2014 at 2:13pm

pfarah77 wrote on Dec 6th, 2014 at 3:10am:
Dave,

I found the car actually is more responsive and gets better gas mileage.



Patrick, please don't take this the wrong way, but this is in your head. If you're getting better mileage with 93, then you're driving differently. NA 944 cars have, at most, 10.6:1 compression, and I'm certain that yours is under 10:1. You cannot burn the octane in 93 fuel. Therefore, each gallon of gas you put in your car has less gas and more additive. Since our cars literally waste the octane, you cannot get more mileage from less fuel, unless as I said before, you drive it differently.

I have tried every variety, brand and octane rating of gas in our cars, Turbo and NA. The best blends for NA cars are non-ethanol 87 or 89 fuels with ethanol. The extra detergents in the 89 and the octane have some isopropyl that absorbs the ethanol. There is much less unburned fuel. Turbos need to run premium, but not for the octane, instead it's to prevent knock and resultant detonation again caused by ethanol. at 1 bar, the cars only have 8:1 - 8.5:1 compression, and boosting, the equivalent is about 12:1. They can burn the octane, but it's more important that there's no water.

I will share a secret right now - If you guys want to try something out of the box and see some real results, go to a marine or auto store and get a bottle of Stabil Marine Ethanol treatment. Add it to 89 grade fuel at it's recommended dilution. Wipe the orange sweat from the inside of your oil filler cap. In 1-2 tanks of gas, you will no longer have moisture in your fuel or oil and your car will run like it's on steroids. You can do this all the time. It costs less than the differential between regular and premium and is way more beneficial for your car. Don't blab this out, it's my trick and I count on the better performance on track days.

Title: Re: Fuel type/grade for porsche 944?
Post by pfarah77 on Dec 6th, 2014 at 11:52pm
Jason,

Maybe you're right, I do like spending more on fuel ;D.

Perhaps I had a couple of bad (contaminated) fill-ups in the past which jaded me.

Title: Re: Fuel type/grade for porsche 944?
Post by Chewbacca 911 Burritos on Dec 9th, 2014 at 4:35pm

porschecidal_maniac wrote on Dec 6th, 2014 at 2:13pm:
Patrick, please don't take this the wrong way, but this is in your head. If you're getting better mileage with 93, then you're driving differently. NA 944 cars have, at most, 10.6:1 compression, and I'm certain that yours is under 10:1. You cannot burn the octane in 93 fuel. Therefore, each gallon of gas you put in your car has less gas and more additive. Since our cars literally waste the octane, you cannot get more mileage from less fuel, unless as I said before, you drive it differently.

I have tried every variety, brand and octane rating of gas in our cars, Turbo and NA. The best blends for NA cars are non-ethanol 87 or 89 fuels with ethanol. The extra detergents in the 89 and the octane have some isopropyl that absorbs the ethanol. There is much less unburned fuel. Turbos need to run premium, but not for the octane, instead it's to prevent knock and resultant detonation again caused by ethanol. at 1 bar, the cars only have 8:1 - 8.5:1 compression, and boosting, the equivalent is about 12:1. They can burn the octane, but it's more important that there's no water.

I will share a secret right now - If you guys want to try something out of the box and see some real results, go to a marine or auto store and get a bottle of Stabil Marine Ethanol treatment. Add it to 89 grade fuel at it's recommended dilution. Wipe the orange sweat from the inside of your oil filler cap. In 1-2 tanks of gas, you will no longer have moisture in your fuel or oil and your car will run like it's on steroids. You can do this all the time. It costs less than the differential between regular and premium and is way more beneficial for your car. Don't blab this out, it's my trick and I count on the better performance on track days.


Yep, Jason nailed it.  Octane is the resistance to igniting from compression.  However, this also means harder to burn.  High compression motors use high octane fuel, and can burn it all.  If you're using too high of an octane on a lower compression motor you can't burn all the fuel.  The result is less burn, wasted fuel, wasted power.  Agreed 100% with Jason here, it would because you are driving different (placebo effect), not because of the gasoline. 

Some years go some of the guys on a motorcycle community had this discussion and finally dyno'd the results.  Lower compression motors with high octane gas made less power, period.

Title: Re: Fuel type/grade for porsche 944?
Post by pfarah77 on Dec 10th, 2014 at 2:32am
Thanks for the explanation guys.

Title: Re: Fuel type/grade for porsche 944?
Post by vintageant on Mar 2nd, 2019 at 6:13pm
OK, old thread, but just found.

Who is using Rec 90 gas in their 944?

Title: Re: Fuel type/grade for porsche 944?
Post by Springgt on Mar 3rd, 2019 at 6:17am
I've used regular 87 octane fuel in my '84 since it was new with zero problems.  That is what the owners manual specified.  It runs great on it.  Every 5-6 tanks, I also add a bottle of Chevron Techron fuel injector cleaner.

Both regular and premium contain pretty much the same number of BTU's per gallon which is why they both get pretty much the same mileage.  If your engine doesn't need the additional anti-knock capability of premium fuel, don't buy it, as it is just a waste of money.





Title: Re: Fuel type/grade for porsche 944?
Post by SactoJohn on Mar 19th, 2019 at 4:42am
91 Ron = 87 US. Unless you change compression higher octane isn't going to run any better. If you have a smog test in your state it will usually have a higher reading with higher octane in an engine not designed for it so if you are on the borderline, you might actually fail the test thinking you would buy "the good stuff" for the smog test. Ideally you don't want the fuel burning too fast or too slow so buy the fuel the engine was designed for. Unfortunately, in CA we are stuck with 10% ethanol in our gas unless we buy racing fuel for $$$. It runs fine in my 944, but it evaporates after sitting a few days in my Edelbrock on the truck and it vaporized in the 280z I used to have whenever I parked somewhere longer than 5 minutes.

Title: Re: Fuel type/grade for porsche 944?
Post by OhioTom on Mar 22nd, 2019 at 8:04pm
US octane is an average of research and motor.
It is posted on the pumps (R+M/2).

Having said that. I have raised the compression on both of my 944's as well as added Wilks performance chips.

Now it does make a difference if I do not use higher octane fuel.
She needs mid-grade. Runs best on Premium.

Price you pay to run higher compression ratios...

Title: Re: Fuel type/grade for porsche 944?
Post by Brainiac on Jun 14th, 2019 at 9:39pm
….well I just wanted to chime in on an experiment I am undertaking...mine is an 84 n/a that I have had for six years...up until recently I have always put in either regular or more often midgrade Chevron, taking the advice of those who seem to be in the know here...I make it a point to use Green Marine Stabil as well, been doing so for about 4 years...about a month ago I finally got around to looking in the manual for recommended fuel, and then looking at the Chevron pump, I interpreted it as saying ( perhaps erroneously) minimum 91 octane so I put in 92 Octane Chevron Supreme....the first tank only took about 8-9 gallons...anyway I had a 150 mile business trip to take the next day....the road through Eastern WA State was two lane with very little traffic, some big canyons, hills with lots of curves and straightaways...I was being bad and I drove it very hard and very fast while constantly looking for law enforcement....I had not done that in years...on the return trip I took a different route with lots of 30-40 MPH curves that I was easily doubling the speed...never got out of 4th gear for 15 miles...after that road, then I was on the interstate and kept it at 75 and under....with this car I have never gotten better than 22 mpg...when  I stopped for fuel, considering how I had been exceedingly breaking the law for about 200 miles, high revs for a lot of it, I was expecting mileage in the upper teens at best...I was shocked at seeing that I had gotten about 24.5...I cannot really tell about more or less power...it has always run great for me and I am not a good judge of things like that...since then I have been putting in Chevron Supreme 92 octane...mileage is always between 24-26 mpg...and I drive it like I always have...I take it easy most of the time, but on certain roads, on ramps and when passing, I have fun and drive it hard...as far as  know, this motor is plain jane but when I bought it, it had an exhaust header, I replaced it a few years ago, and last year when repairing a ruined camshaft and timing gear I discovered a broken valve spring...Lindsey Racing rebuilt the head and gave me a deal on turbo valve springs...so with the better mpg, at least I am not paying more out of pocket for premium, but am I doing any harm?...I am going to switch back to midgrade (89) next week to see if I notice anything...

Title: Re: Fuel type/grade for porsche 944?
Post by OhioTom on Jun 24th, 2019 at 6:11pm
No harm...
Hey, if your car likes it, that's all that matters.
Every motor is different.
Carbon buildups. A/F ratio, REAL compression ratio, variation in manufacturing... All can make one motor behave differently than another.

It can all play a part in how "detonation sensitive" a motor is.


Both of my 944 cars get 24-29mpg depending on driving style.
never seen one get in the teens. Something is not right about that...


Title: Re: Fuel type/grade for porsche 944?
Post by Brainiac on Jul 5th, 2019 at 3:00am
….well...my experiment is over...the last couple of tanks my mileage with the premium Chevron never got above 23...that tells me it was probably more to do with my driving style...and on a couple tanks it was great...but perhaps I was fooling myself...I have gone back to mid grade Chevron...and though I mentioned that I am not a good judge of power comparisons...it does seem to be running stronger and more fun as a result...and if I stick with it...I will save money!!! ...I wonder if gas varies from location to location...even if it is the same brand...Thanks again Ohio Tom...

Title: Re: Fuel type/grade for porsche 944?
Post by OhioTom on Jul 8th, 2019 at 5:28pm
Yes, fuel quality can vary alot..

In Ohio, fuel "may have upto 10% Ethanol" in the regular grade.
All depends on what that station buys from the dealer.

yes fuel dealers sell all kinds of grades of regular gasoline.
Even "off spec" stuff is sold to cheap stations to dump it.
My Brother works in the industry and tells me they make over 100 grades of fuel for the USA. Each state and even Cities can have thier own specs on fuel.

Meaning: It may, or maynot have ethanol.....

great...

One reason I am not afraid to run premium. The quality is much better, and is always 100% GAS.

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