Gotta love the internet, Facebook group rant Options

[IronHillRestorations]

The first time we had a Renegade Festival in Hot Springs (2nd mid west event), I lucked up and got a tech rep from BG Petroleum Products to give us a tech session. BG (was Wynn's Spitfire) makes fuel and oil additives. Their fuel additive is very effective for helping remove excess carbon build up. This is especially a problem in Japanese cars, or at least it was 20 years ago. He had quite a bit of technical data and, was there for a Toyota, or Honda tech summit of sorts. I saw him getting stuff out of the truck with a big BG on the side and started asking questions, and he graciously agreed to give us a tech session.

The guy did a cool "Mr. Science" kind of demonstration showing the difference between regular and premium gasoline. The demo showed that regular gas burns faster and cleaner than premium. He put a small eye dropper of each fuel on their own white Corell saucer. The regular burned without a lot of smoke and left a little residue. The premium burned slower, made noticeably more waxy like smoke, and left much more residue on the plate. Part of the point is to demonstrate that gasoline octane is the opposite of what most people think, "high test" or "the good stuff" is less volatile and has more additives. High octane fuel is the same fuel as regular, but with an additive package to lower the volatility, raising the octane for higher compression engines. He went on to say that you should use whatever your auto manufacturer recommends, and if no solid recommendation the general rule of thumb is to use the lowest octane you can, without getting pinging, or pre-ignition. Using high octane fuel in an engine that doesn't require it, can result in more unburned fuel, that can cause carbon build up in the combustion chamber, raising compression, and thereby requiring you to use a higher octane fuel that adds to the problem. Make sense? Are you tracking with me?

Most all of the guys there had questions, as well as their minds changed about the best fuel to use, in any car.

Someone posted on one of the 914 FB groups asking "what octane fuel should I use". My reply was based on my own experience, but mostly on the info from the BG rep: "Unless the mfr or engine builder says otherwise, you should run the lowest octane you can as long as you don't get pinging, or run on. Octane additives typically translate into carbon build up in the combustion chambers." Good grief, you'd have thought I said there's no Santa Claus, or our 914 is just a VW.

I've been around these cars for a while, and cringe whenever I get called an "expert" or "guru". Part of the great thing about our internet 914 community is we get to share insight and experiences both helpful and otherwise. Most everyone of us that's been elbows deep in a project has something good to share, even if it's "man I really messed up" But some people have to tell you how wrong you are, even if you aren't far off the mark, I don't get it (IMG:style_emoticons/default/blink.gif)

[Dave_Darling]

Well, atmospheric pressure at somewhere near sea level. (IMG:style_emoticons/default/wink.gif)

What's interesting is that the combustion speed is not dictated by the octane spec, so it is possible that premium could burn faster than regular. Vanishingly unlikely, and probably would require some PhD chemist specifically trying to make that happen, but it is possible.

Anecdote time: Once upon a time, they built aircraft engines specifically to use ~80 octane AvGas. Many years later, this became hard to find. Some folks just decided to stick 110 low-lead in their plane and call it done, because new engines cost a ton of money (and re-certifying your engine for car gasoline, which can be found with a reasonably acceptable level of octane, also costs a lot).

All of a sudden, there were a whole lot of burned exhaust valves showing up in those engines. Turns out the high-test stuff was still burning as it went out past the valve, heating up the exhaust valve and related bits (seats, guides) a lot more.

So those folks got to buy themselves new engines anyway... Oops.


I strongly suggest that nobody put 150-octane fuel in their stock 914... (IMG:style_emoticons/default/biggrin.gif)

--DD