On my 74 2.0L, I have MPS (Part#: 280 100 043). I am not having an existing problem with my MPS, but with today's gasoline (ethanol blends, etc..) should an MPS be recalibrated for optimum operation? I typically fill up with Chevron 91 premium.

Of course, if it's not broke then don't fix it...

You're probably OK. Running 91 octane fuel is most likely a waste of money unless you're running pretty high compression. The correct version of your last sentence is "If it ain't broke, fix it 'till it is". 914 guys follow that one a lot.

The Cap'n

Probably? Probably?!!! Haha! Just kidding.

What's everybody running on their stock FI systems? Mid-grade 89? Or 87?

Back when I had a BMW E36 M3, I once calculated that running the 91 premium fuel for a year costs about $400/year extra (assuming aroudn 15K miles/year.) I suppose that's $400/year I could be putting towards an eventual engine rebuild.

87 in both the /4 & /6 everywhere and never a problem except at a no-name gas station with tanks full of water.

I use 87 octane as that is what the car was designed to run on. Save the money and add a wideband A/F mixture gage. You will then know if you need to adjust your MPS. I have a 76 with a calibrated MPS but was still running lean until I made the adjustments to richen it up.

Just my $.02

Hi - I'm glad this issue has come-up because I just bought a '76 2.0 with injection and pollution controls intact - found on 914world! I wasn't sure what to run and the previous owner had said 89 at most. I had assumed I should run higher and the little sticker in front says 91 but the octane rating were different then? Thanks.

Germany calculates using the RON (The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.)

The US (uses In most countries, including Australia and all of those in Europe[citation needed], the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON).)

Because of the 8 to 10 point difference noted above, the octane rating shown in Canada and the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. This difference is known as the fuel's sensitivity,[4] and is not typically published for those countries that use the Anti-Knock Index labelling system.

So the 91 RON octane rating in Germany is about the same as 87 in the US.
RON x .95 =~US pump Octane.

Thanks very much. So, using anything with an octane rating above that doesn't help performance ..and it's been suggested to me, may be harmful ..or is it just a waste of money?

I have been running 87 octane pump gas (with ethanol) in my stock 74 2.0 D-jet for about 3500 miles with no problems. I have never fiddled with the MPS and I believe it still has the factory settings.

Bought a rebuild kit from Tangerine Racing and with the intent to get a spare fixed & calibrated. Will be a winter project.