What octane do you run?

[Monkey Wrench]

ive been using chevron 91 here, its the most we can get at the pump. in all my old beat up cars from the 80's because I believe it's the only one we can get without alcohol added. My brother was a Harley mechanic and he said he has less problems with people storing and associated fuel gunk collecting in the carbs whit that better fuel. HE said the new gas just doesnt; smeall the same and it goes sort of stinky, doesnt; store so well..

back some years ago I was running gas with alcohol in it and when I pulled my engine apart it had suffered lots, broken rings etc. I couldn't blame the fuel exactly but I stopped buying it. I felt it was a bit corrosive or maybe washed away oil. alcohol is not a great lubricant.

I always figured Id jut pay the extra and maybe keep the fuel system clean. I sometimes switch cars for a while so they sometimes suddenly fail for some reason then sit a year or two. sometimes ill add some fuel preservative stuff. I started buying it for my gas can and add the conditioner to 5 gallons then maybe top each car up a little to get some in there.

I found they stumbled less , sometimes Ill buy a lower grade but then I seem to get more erratic idle etc.

last time I bought premium it was $2.79 per liter. Its been going up like crazy. It dipped a bit since last week but every time I fill Up I feel like I'm "property poor" everyone is running around near empty watching prices.

I've heard said higher octane than you need is akin to buying shoes too big but I wondered what others thought and what they choose to run, and their reasoning behind their choice..

lots of people say it's better to store a car full of gas than half empty or empty the reasoning is that then there is less air in the tank and it's the air that causes moisture It makes the tank 'sweat" inside and the water pollutes the gas and rusts the tank out.
If you store your car a lot then you have a whole tank of gas to burn up before you can get fresh gas so it could mean a long time before you use it up. do you keep your tank full?


would you put better gas in a "good car" as opposed to a beater? do you follow the OEM recommendations? I know if you raise compression you might also want higher octane to prevent pinging.

racing and race fuel , that's another thing altogether..

[Dano944]

Since my 944 is a weekend driver, I use the highest octane. I’m not even sure what the owners book recommends, except “Use unleaded”. Here in California Premium is now $6.80/gal, thanks to Mr Potato Head, but since I don’t drive that much, I just bite my tongue once every few weeks.

[OK-944]

I've had great luck with mid-grade gas for my '87NA (driving about 500 miles/month). AFAIK regular grade would also be appropriate for my car, but I decided awhile ago to use mid-grade.

But unless the use of a premium grade gas is specified for your car, then you are likely throwing money out the window.

[Jfrahm]

I had some old Saabs I used for testing turbo mods and what I found was that octane matters a lot less if at all in cool or cold weather. And it matters a lot in hot weather.

Yes if your car is not designed to use premium and is not packed with carbon deposits, raising the compression, it's just lighting money on fire to use higher octane than needed. It should also reduce MPG a bit as there is less energy-per-unit-volume in the premium gas as the octane increasing compounds take up space in your gallon of fuel.

I have a 944/S/Turbo glovebox manual handy and it says:
944: 91 RON (euro measure) or 87 R+M/2 (USA style measure)
944S/Turbo: 95 RON or 90 R+M/2

(Fuel capacity is listed as 21.1 gallons or 80 liters in this manual for 1987 or 1988 cars)

Here at altitude we get 85 for "regular" instead of 87 or 88 and that's OK due to the lower atmospheric pressure. I personally would not run midgrade in hot weather in an S or Turbo
Might not run regular in July in a 944NA either. Probably at least midgrade.

I also learned that shady stations are shady and their premium and midgrade might not be for real all the time. In hot weather particularly, with a car that might not have enough timing authority to not ping on regular, avoid the cheap and unaffiliated stations unless known to be good as per your local modded turbo car scenesters.

-Joel.

[Monkey Wrench]

interesting that the gas stations would change what they call "mid grade" because of their altitude. I guess it probably still says the octane at the pump.

Ive actually never had gas I couldn't run out, even when a car sat a couple of years it still seemed to burn the stuff.
with whats being said I'm thinking of dropping at least to a mid grade, my cars dont call for 91, maybe I fell for the Chevron ads and figured a higher grade might prevent injector and pump issues and so forth. I usually use chevron because I hate inputting a list of questions, no I dont want a car wash etc.
a few times Ive bought gas and the pump seemed to have been slowed down. a couple of times I got fed up and left because the pump is so slow after filling for about 15 mins.. maybe they slow them if they are running short on gas.

some of the stations here leave the little tab thing on the pump handle so you can flip it up and let go then wash windows etc but many seem to remove it so you have to stand there glued to the pump handle, which i find a little annoying.

I dont notice the problems so much in cars but It's really common to see small engines with gummed up carbs due to the gasoline varnish or whatever you call the crud. I just try to run any small motor right out of gas, Can't easily do that with a car.

occasionally Ive put a half bottle or so of sea foam in a full tank of gas, to try to clean the injectors. Its hard to tell if it does anything. spraying it into the manifold might help clean the valves etc. maybe getting it into the fuel rail helps better with the injectors than adding it to the gas. maybe I need a fixture to do that.
Ive heard said that if you pull an engine apart and first treat the oil with sea foam it does make the engine cleaner.
I have not used synthetic oils. they presumably are better but Ive always felt that more regular oil changes help enough. some seem really sold on the more expensive oil. sea foam might not be necessary in the oil if you don't let the oil turn all black.

My 944 has a gas line from the tank that turned to mush. I figure it goes to the filter and pump then into a higher pressure line with threaded fittings.. past the pump. is that line as susceptible? I've never seen that high pressure line fail or break down in other cars since it's not a rubber line , probably like a thick plastic with a covering. my ford van has really stupid clip things on the line junctions. I had issues with it leaking gas onto the road due to those a few times. it's an 88 with a 3.9 L 6 love the engine but it's like driving a house around with raised roof etc. I made the mistake of going for a cheapo pump in the ford, and it seems to start making vibrating noises. no more cheap pumps, the bosche ones are a lot more heavy duty I think. Probably not the best way to save 100 bucks by using the Chinese ones.

Ill have a look for old rubber hoses around the engine. Vacuum leaks etc. I can have a better look when I'm doing all the rubber belts. I'll need to learn more about this injection system, and clean and replace what's necessary. maybe some are just hose, and some might be specially molded hoses. Ill try to avoid going in too deep at first. Id rather see how it runs and then of I start working on other stuff at least I have a better idea having tested things and proved it to be operational and free from other starting issues. I bought it knowing it has a starting issue aside from the gas line degradation. could just be a bad DME relay. he said it ran fine until it failed to start, then sat but the cause wasn't looked into so it likely is not a show stopper.

I think i should connect everything except 1 wire to the pump then do the belts, then see if the pump has power. a squirt of oil in the cylinders might be good for it's initial cranking and then I can change the belts before getting too excited and trying to start it. I gave it a little click to see if it would try to turn and it did prove it's not seized up, so I stopped myself there. with my old volvo I can pull the distributor and run the pump with a shaft on an electric drill . that might be good, to get oil pressure up into the journals, and then start it after but that might not be so easy to do on a Porsche. Its something Id do after assembling a fresh engine or in this case, because it sat for a long time.





If I need to pull the injection system apart to clean it or the throttle body or maybe a intake manifold gasket, i'll get to those things after.

the weather will change soon and my car is in a tent which I can;t really heat, so I might be able to pull some of the parts into my basement shop and work on stuff over winter. If it takes a while I'm prepared for that.

[J1NX3D]

I use 95 RON in my previous RoW 8v engine and my current 968 engine but 98 and 100 RON are also available at some stations here in NZ. The 100 RON is ethanol-free.

[v2rocket_aka944]

if its a US spec 8v 1983-1987 - use 87 octane regular.
if it's a 1988 or 1989 8v (high compression engine), use 91 or higher.
if it's a 16v 944S, 944S2, or 968, use 91 or higher.
if it's a turbo, use 91 or higher.

ALL gas will have 10% ethanol content minimum in the USA unless the station specifically sells it as ethanol-free gas, which is usually about $1 more per gallon than plain E10 standard fuel.

[Dano944]

My Smog Check guy told me to run Premium to help with the emissions test. Regardless, that’s what I run anyways.

[924RACR]

93 (R+M/2) in my street 924 Turbo - running double stock boost and 'squirted, of course.

Racecars get 100 (R+M)/2 - either unleaded, when I can get it (only at the racetrack, unfortunately), or a 50/50 mix of 93 unleaded from the pump and 110 leaded race gas (which ends up cheaper, but I don't like because lead is nasty)...

[Fast Freddy 944]

High test corny gas is what we put in our cars. Its crap dippy hippy gas and it destroys fuel systems for lots of vehicles. 91+ fuel goes in my hot rod 951 and a good bottle of ethynol remover per tank. Its not a daily drive since its a fragile machine. Go big or go home.

[djnolan]

to get 91 octane can I mix grades - half 93 and half 89 octane?

[v2rocket_aka944]

Originally Posted by djnolan

to get 91 octane can I mix grades - half 93 and half 89 octane?

yes

[originalowner]

If your gas cap cover or owner's manual says to use 91 RON, that is the same as 87 (R + M)/2 octane, as labeled on the pump in the US. Yes, the car was designed to run on regular gas. I've always run premium, but it is not necessary. At all.

[Peter Graham]

Here in NC and surrounding states, we have Quality Plus/GoGas stations that offer 93 octane no-corn fuel (used to fill 912/951). Here in the Asheville area, price was $4.60/gallon yesterday. When out-of-area and no-corn hi-test fuel is not readily available, I will use top tier premium fuel (Shell, Chevron).

Peter