So what kind of gas should I be putting in my car?

1973 1.7 bone stock car with fi

Regular.

+1
I use it in my 2.0L too

dude your fast thanks ,now i'm in sunny cal so what about makers. you acro shell etc...

Chevron and Mobil have the best fuel system cleaners. Shell has traditionally high in sulfur (not good for Bosch injectors), but I think that's in the past since the smoggies really got down and serious. I don't like ARCO for a number of reasons, some philosophical, some because of their additive package. A former big weenie at ARCO was on the Air Resources Board and suckered the state into using MBTE, that wonderful additive that poisons our water systems and happened to be under an ARCO patent. We're gonna be paying for that for about a thousand years ..................

The Cap'n

Thanks cap, but 87 is ok?

The octane in fuel is increased to prevent pinging/knocking. Your bone stock, low-compression 1.7 doesn't get anywhere remotely close to pinging, so higher octane in literally throwing money out your tailpipe.

Premium fuel is NOT 'the good stuff'.

that's what I like to hear

MBTE also "eats" the rubber in lines & grommets/gaskets/seals exposed to it. I used to have to re-gasket the top of our 88 Westy fuel tank every 2-5 years while they used it here in CA!

I mostly use ARCO in the 88 VW Westy (bone stock 2.1 L EFI waterboxer) & 85 BMW 325e (also stock EFI I-6) -both on 87 Regular - no fuel related problems to date in 206k & 176k mi respectively since new.

My 73 914-2.0 says 91 RON, so I guess I'll use Premium in it when she's running again, but 8.0:1 doesn't seem that high.

However, I don't know if the fuel additives they sell to add per tank do any good.

When I was in the US the first time I filled up i saw this 87 Octane ethanol crap, i serriously doubted you could even make a Molotov out of that stuff, then I discoveed Phillips racing gas (petrol), fantastic...

To answer the original question, 87 octane regular gas is perfectly fine for a stock 1.7 914.

91 RON is not the same as 91 AKI. You guys that think your stock 914 needs premium fuel in the US simply because the sticker on your car says 91 RON, really need to read about gasoline octane ratings, past and present, US and Europe. DOn't take my word for it. Just keep wasting your money.



Not to nit-pick, but it's MTBE and not MBTE isn't it?

What if youre running dual webber would that change the ball game? Or Still use 87.

Yup.

The Cap'n

Since you're already getting poor fuel mileage with Weber carburetors (note the spelling of 'Weber'), unless you've raised the compression you should be fine with 87 octane. Or maybe you like throwing money away and increasing the amount of unburned fuel leaving your tailpipe.

The Cap'n

I was introduced to Tektron FI cleaner by a 38 year master mechanic that swears by it. I tried all the others,,,nothing does what this magic juice does.
Since then, I run everything on regular and use Tektron about once every three months.
The only exception is my bmw which I put in two tektrons and a tank of premium octane every three months..then I do an old fashions carb blowout session on a few onramps...that motor is a bit different than the rest.
My Volvo has 270k miles, bmw has 220k miles, eurovan has 180k and 914 has 140k....they all run fine.
I also use old fashioned dino oil from Walmart on all of them...never had a problem. I shop for oil based upon weight and price.

I have read all the oil reports and given my personal experience with over 100 cars...and my long life motors (I change my oil at least twice per year...honest) I am happy with the money I have saved by not being drawn into the synthetic oil and premium fuel camp.

Rich
Rich

Techron (correct spelling) comes free with every gallon of Chevron and Mobil gasoline. ...............................

The Cap'n

No idea where to get Chevron Gas around here...
Mobile...not sure its in that fuel...could be or not.
I found adding it once in a while does the trick...then I use chaper fuel the rest of the time, and that was the point...

Rich

Very cool, thanks for all the help.....I know very lil about gas....pump gas that is.

To expand upon the Cap'n and my earlier post...

Octane is a detonation/pining prevention. Detonation/pinging are related to engine compression which is set when the motor is built and doesn't change (slight simplification). Nothing you bolt on (carbs, FI, exhaust, chrome engine tin, etc) is going to change the compression ratio, except a turbo or supercharger.

MTBE (not MBTE) poisoned the water because the tanks leaked. The tanks shouldn't leak. MTBE was only a small percentage of gas, which is not exactly mothers milk in its own right, having the known carcinogen benzene, among others. Wells in the LA area continue to be closed due to other solvents that are worse. To the extent that MTBE renders gas more soluble in water is also true of its replacement, ethanol, which has its own bogus rationale and cast of sordid weenies.

I have nothing to add to this thread except that somebody should use this as the name of their band.

To continue this interesting (to me, anyway) sidebar conversation, MTBE is one of the most water-soluble components in gasoline (if not the most soluble component), though it doesn't make any of the other components of gasoline any more or less water-soluble. It's because of this that it actually can be thought of as a pretty good indicator of "trouble ahead" when it starts being found in groundwater, though MTBE itself is not a carcinogen and is relatively non-toxic.

Other components that are much less water-soluble but far more carcinogenic are toluene and benzene. They are spilled from the same gasoline spill, and are more slowly following behind in the same plume that the MTBE was at the vanguard. So in a way, MTBE could be used as an advance indicator of a problem, and I wonder at the logic of removing it completely from fuels. Removing MTBE entirely, at least in my opinion using the logic I just stated, might be penny-wise but pound-foolish if there is not another advance indicator of the plume spread such that we could stop it before the real bad actors (toluene and benzene) reach groundwater. But it seems that decision has already been made.

Of course, all of that discussion is about the relative risks of spilling too much gasoline which is besides the point when one is talking about engine performance. I think most places in the US add ethanol these days, though it could become more cost-effective to just add iso-octane itself (still much more expensive than MTBE) or even ETBE (ethyl tert-butyl ether) as they do in Europe (as I just read). Incidentally, I wonder how many engines out there really need higher octane fuels or is it all just a big marketing scheme? I certainly don't see much need for high-octane fuels in n/a motors at the altitudes I live in (same goes for all of us in the Rocky Mtns), almost regardless of compression ratio.

- Nelson

Always use the LOWEST octane you can without pinging.

This is probably 180* from what you may think: Higher octane fuel is better for my car, it's the good stuff and costs more, so it has to be better right?

The lower octane fuel has fewer additives, which results in a cleaner burn and less carbon build up in the combustion chamber.

"High Test" or high octane fuel has more additives to make it burn slower, and these add to carbon build up on the cylinder head and top of the piston. Extra carbon build up raises the compression and causes pinging and starts the whole vicious cycle.

Techron is a good product for cleaning the combustion chamber. There is also a whole line of products from BG Petroleum designed to help remove carbon deposits.

Hey, it was dark and my fingers couldn't see ............... The biggest problem with MTBE is it aggressively seeks out water. While some wells and industrial sites are most assuredly closed for other solvents, we actively made sure that, wherever gasoline was sold, dispensed, spilled when filling a chainsaw or lawnmower, or anything else, or leaked out of ANYTHING, it was headed for the nearest water. And we did it on purpose. Everywhere. Off road bikes, snowmobiles, personal watercraft, the aforementioned lawnmowers and chainsaws, all spread it to every corner of the state.

The Cap'n

GAS???? yeah I have some, want to smell it? pull my finger

Thanx Gint - I forgot about that factor!

By 73 MY CA was requiring all cars to run on unleaded 87 octane - remember the different pumps with the smaller nozzle to differentiate & not allow you to put "old gas" in your car? There was also a change to the rating system in the USA about that time which showed a lower rating than for the old 60's & earlier system, per my Dad who was a Petro-Chemist in his first career.

So the 4-5+ lower AKI/USA octane rating on87 equals or betters the 97 RON. Also IIRC for the 2.0L's the GA was a bit lower 7.6:1 compression ratio, while the Euro heads were the 8.0:1 on the GB motors, & therefore turned out 100 hp vs. 95 in the GA's.

So I suppose the 87/Regular is fine for my 73 2.0 also, unless it starts pinging/knocking with the current products, and even then I'd first check out the octane enhancer additives etc. for older cars first, before buying higher grade gas. I did run 87 unleaded during 80-85 in it with no problems.

Nelson, good info.

However, while MTBE is not as bad as the others, the jury is still out on its health risks - esp. in the water supply, which is 80% groundwater here in my town - Orange, CA. In Brownfields Redevelopments in which I've been involved, we still need to remediate for it per EPA in order to get site clearances for redevelopment, but it's tenacious in the way it quickly passes through the soil & spreads so quickly, that it's like herding cats/chickens according to our remediation engineers.

As for keeping it as a marker, the problem is - & was known by ARCO from the start - that it eats at the rubber (both natural & synthetic) so that fuel lines, gaskets, seals & grommets, etc. are prone to early failure, and therefore results in more surface spills from vehicles on the roads & off-road. As I stated earlier, I've had to reseal the 88 Westy's gas tank 3-4 x during the time which CA used MTBE additives.

.... don't try that near an open flame or spark!

As a registered Environmental Engineer, water resources and superfund investigation/ risk assessment specialist, Registered asshole (see pole), and authentic old coot, I will state that MTBE failed.
It leaks more easily than gasoline, implying that OK systems are bad, so needed cleanup $ go to false failures.(there is a 2 feet deep plume of petroleum under Phil PA. over 1 foot of petroleum product cover 100s of square miles of groundwater in southern Cali -these are much greater sources than some gas station leaking MTBE. Oh, and then there is NJ...). It eats distribution system (big industrial and individual engine) components. It MAY be carcenogenic, so it is considerd so by EPA risk assessment processes. MTBE was another "science will save us, so we don't have to act responsibly!" delusion, foistered on us codependant users. Bad objective, bad execition, and manipulation of a willing public. I'm glad it got stopped. They are still trying all kinds of chemical, physical, and biological "fixes". Some may work. But some may provide employment for the next gen of Enviro Engineers.

gas,grass, or ass no free rides

I actually had a discussion with a state inspector on the different fuels. In his opinion, there was not enough of the "fuel system cleaners" per tank to make much/any difference. He said to buy the cheaper stuff and run a bottle every few months of good FI cleaner. Now, I do see about 1-2 MPG less in my Jeep if I run Safeway gas vs a little better quality, but Safeway is all I have next to home.

detonation is also related to temperature of combustion chamber (run to hot and it happens) and too much advance with cuase pinging. higher octane can help reduce these effects and allow hotter temps and more timing advance.

That's not so bad, you can't eat gas, 'least you wont starve.

Safeway? that was a super market back in the day.

The Porsche 914 Workshop Manual (group 0 1.2-1/2) states:
required octane rating: 98 Oct. (premium fuel)

...so if today's octane ratings are 10-11 points off from the old method, does that mean that today's 87 octane is equivalent to 1970 era premium (98 octane) and that the old school high compression engines should run 87 octane??

I have not really read this thread.
But I am not going to put ethahol in my 914 unless I am somewhere
that I cannot find alcohol free gas.
Case in point.
I was running the alcohol gas in my 94 4 runner.
It kept loseing power.
After about 2 years I put real gas in it and the power doubled.
Or so it seemed.
After that I only use real gas.
John

Still is...

Safeway is The most common supermarket in N Cal

Gary, that's probably for the early & higher compression non-USA motors. Also note on the next page or so that the 914-6 is listed at 98 octane premium.

The stickers on the pass. front wheel house next to the tank is 91 RON, which as Gint pointed out earlier, equals the 0ld 1970's 87 Regular. Also gasoline formulations were different then, different USA vs. Europe, as compared to now.

For those worrying about +/-10% Ethanol as a smog control additive, most testing I've heard about says that it's not detrimental to performance until it reaches 15-20% for non-Ethanol engineered motors (such as the Chevy dual-fuel ethanol models out today). What caused the poor performance in the 4Runner above was more likely a higher % &/or a bad blend (refiners have been known to cheat on octane, especially smaller ones & independent dealers).

I run the 91 but I'm also running about 10#s of boost

I could prolly push that to 14#s if I ran the 104.

10% ethanol IS determintal, reduces milage in any amount, it has less energy content that the gas it replaces.

from an envirometal standpoint it is also a losser, more valuable land wasted on growing the stuff to make it, petrochemicals needed to fertilize and rid the land of insects, and the energy needed to turn the crops into ethonal all have an enviromental toil, ften over looked when we talk purely about tail pipe emmisions.

plus since the fuel has less energy content, more gallons are burned, which means more tanker truck are needed to haul the additonal volume of fuel.

the added cost of ethonal is tax payer subsidized, last I heard it was near $0.60 per gallon of pure ethanol that teh big agri/chemical industry gets form us for that stuff that delievers lower mpg, and harms automotive parts.

The use of ethanol in the fuel has lead to food price increases, particulary hard on some poor nations south of us, the price or corn went up there and that was a big hurt.

We need to keep this bad crap out of our GAS tanks. bad science, bad policy.

What if you are running 2.0L pistons and cylinders? Still 87?

Just run the lowest octane you can without pinging. Buy a 1/4 tank of regular and see how it runs.

Get a little 'test gas' and see how it runs. If it runs like crap, fill it with whatever you have been using and it will dilute sufficiently to go back to normal.

Knowing the actual compression ratio is the key. Having a 1911 built with 2.0 P&C doesn't truly mean anything. The compression ratio could still be anywhere from 6 to 10 depending on how it was built.

Sorry, I meant to ask about a 2.0L with higher compression euro pistons and cylinders.

Realred -

My comments above were not directed to world economics, taxpayer subsidies, feeding the world & PC issues. While I don't necessarily disagree with all of those points & issues - nor even that non-ethanol fuels are better for some cars, especially older ones - , but the the current REALITY that we in CA are REQUIRED to run the only currently allowed fuel mixture with ethanol!

We simply have no choice, and I commented it was not MECHANICALLY detrimental to the motors/etc. in smaller %'s.

As to lower mpg/power - IF your contention is correct about lower mpg, then with ethanol blended gas at 10% max. (as here in CA) & it's 80-90% as efficient as "pure gas" - then you're really only losing 1-2% of mpg & power produced if my math is right - 10% of 10-20% lower.

That said, other additives in the ethanol blends are supposed to keep the octane levels at 87/regular, 89/mid & 91/premium standards respectively, and since the octane rating measure the energy content of a particular blend - the power/mpg potential for 87 ethanol should be the same as 87 gasoline-only blends - 87 is 87 by the tests/math.

BTW - Pretty much all of our food in the USA is taxpayer subsidized - either directly or with cheap Federal water projects, etc. - whether is corn for food or ethanol, or other meat & produce - and has been since the 1930's.

Like Mark said above, it depends upon the actual compression ratio of your engine build.
Then you can compare that to say mfgr. reccos on a Euro 2.0 (maybe a Euro member/owner has their owners manual that they can tell you, but my info below says 95 RON Premium).

IIRC the stock Euro 2.0 was 8.0:1 & US was 7.6:1 (see below).

FYI All -
Here are the "stock" factory CR's from my 914 Spec Book
- (5/1/74 1st Ed. - so no 75-76 MY info):
Click to view attachment

69/70-70 MY to 71/72-72 MY "W" & "EA" 1.7L's = 8.2:1 w/ 80 hp - 98 RON
> & for 72/73-73 MY Euro EA 1.7L's

72/73-73 MY "EB" 1.7L's = 7.3:1 w/72 hp - 91 RON
> (only about 7.0:1 w/ 69 hp in Calif 1.7L's - IIRC)

73/74-74 MY "EC" 1.8L's = 7.3:1 w/ 76 hp - 91 RON (incl. Calif)

73/74-74 MY to 73/74-74 MY "GA" 2.0L's = 7.6:1 w/ 95 hp - 91 RON (incl. Calif)
> (73-74 MY Euro "GB" 2.0's were 8.0:1 w/ 100 hp - IIRC)

.

My early 73 MY 914 1.7/2.0 Owners Manual (a new/NOS original replacement purchased in 2009 & in English) appears to be showing the Euro specs EA & GB motors (EA as noted above),
& GB at 100 hp DIN (95 hp SAE) with 8.0:1 - & recco's 95 octane Premium fuel.

For comparison on the USA 2.0L GA spec, the DIN is 95 hp & SAE is 91 hp at 7.6:1 per the above spec book figures.

So you'll hear differing hp numbers on these engines, depending on whether it's quoting DIN (Euro) or SAE (USA) testing/rating standards.

Another factor affecting pinging/knocking & fuel grade is altitude, since the thin air high up exacerbates the problem in some cars.

Interesting thread!

Sounds logical, but having lived in Colorado most of my life, I believe that it's the opposite actually. That's why octane levels of all gas sold in high altitude states (like Colorado and Utah) are two points lower across all the octane levels. Regular gas here is 85 instead of 87, and so on... I've driven plenty of cars (even my lowly carb'd 914) from 5k feet to 10-14k feet and still no pinging on the same 85 octane gas I bought down in town.

Where's a chemist when you need one? Nelson...

One of my childhood neighbors house burned down because the fuel lines in a fairly new car rotted out from MTBE and then the car burst into flames in the garage. They sued the state (Kalifornia) and won the replacement cost of the cars and the home. That vile toxic waste was removed from gas a few years later.
I'm glad my primary transportation is diesel (or vegi oil when it's cheap.)

High altitude = lower combustion pressure. There is simply less 'air' up high. Pikes peak racers have insanely high compression ratios if they are NA. I remember seeing a picture of an engine that had a sign on it stating 'do not operate at less than 6000 ft. altitude. It had 15:1 or higher compression.
Steve