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For classic car owners there are certain topics that consume the internet in both the form of questions and answers. Topics such as “What fuel to use? What octane? What brand of oil? What weight of oil? Should I use synthetic? How often should I change my oil? And the list goes on and on especially when thinking about classic BMWs or classic Mercedes.

Unfortunately as many questions as there are, there are ten times the number of answers or opinions. So where do you turn to get the straight scoop on your car? Only one place, the owners manual for your specific car! While your owners manual is not a romantic, drama laced read, drama and lack of romance quickly ensue when your classic “fails to proceed” on the side of the road.

While many might argue, “times have changed and we now have better and different products,” which I won’t disagree with, the manufacturers directions are still the best, most reliable answers you will ever get. At the very least, the owners manual provides the standard and baseline, should you introduce the latest technology fluids, etc.

ONE IN THE SAME

Let’s look at two of the most common questions from classic car owners. First, what brand of fuel should I use? And what octane is needed? Good questions.

Gasoline sold in the United States must meet specific government guidelines for quality/ additives and are acceptable for your car if stored properly. In short, oil companies pump oil, the oil is shipped to one of 139 refineries throughout the country and sent through the pipeline to gasoline storage facilities. It is then collected by tanker trucks and distributed to the various gas stations around the nation.

The question now remains, when you fill up at Chevron, for example, are you really purchasing Chevron drilled, Chevron refined, gasoline? Most likely, no. According to Platts, all the refineries output flow together into storage prior to distribution. So what makes Chevron, different than say Shell brand gasoline? Simple, at the point of pick up, most branded gasoline retailers add a patented detergent package such as Chevron’s Techron or Shell’s V-Power to the standard fuel prior to delivery, making that delivery, a Shell, or Chevron specific product. Other branded gasoline retail outlets, often add detergent packages, however they are not patented and are generic government regulated additives.

TOP TIER

For example, Costco Gas is rated a “Top Tier” gasoline and according to their advertisements, they add a detergent package that is “5X better” then the minimum government mandated standards. So what does that mean exactly? In order to be rated a “Top Tier” fuel supplier, you must exceed the 1995 EPA standards for detergents which help keep all combustion areas of your engine free of carbon build up and fuel injectors and carbs clean.

So where do we buy such fine fuel? Here is the list of “Top Tier” licensed gasoline retailers according to toptiergas.com: 76, Aloha Petroleum, Amoco, ARCO, Beacon, BP, Break Time, Cenex, Chevron, CITGO, Conoco, Co-op, Costco, CountryMark, CountryMark Plus, Diamond Shamrock, Entec, Esso, Express, Exxon, Holiday, Kwik Star Stores, Kwik Trip, Mahalo, MFA, Mobil, Ohana Fuels, Petro-Canada, Phillips 66, PUMA, QT, Quik Trip, Road Ranger, Shamrock, Shell, Shell V-Power NiTRO+, Sinclair, Standard, SuperAmerica, SuperFuels, Tempo, Texaco, Tri-Par, Valero.

ALL THE SAME?

That now leaves us with just a few remaining loose ends. Are unbranded gas stations like Big Joe’s Gas, as a random example and hopefully unreal example, just as good then as branded? Not necessarily. The further from the pipe line the fuel travels, the less is known about it’s handling and additives. Unbranded stations my not provide the extra detergent package designed to keep the inner workings of your engine and fuel system (injectors) clean, but will more than likely not cause a problem if the fuel is being kept fresh and free from contaminants etc.

KNOCK, KNOCK

Perhaps you find hearing knock, knock jokes funny, but be assured hearing them from your engine is no laughing matter. Engine knock or pinging, is very hard on a gasoline engine. In simple terms, the knocking is the result of combustion taking place at the wrong time by self combustion and timed combustion in the cylinder. These multiple and scattered explosions cause the piston to essentially rattle in it’s socket. Unlike diesel engines that essentially “knock” the entire time they run, hence the traditional diesel clatter, gasoline engines are not built to withstand such violent erratic shocks.

So what keeps our classics from knocking or pinging? Assuming the engine has been properly tuned and all systems are in good working order, octane is what keeps the fuel from wanting to combust too early or at the wrong time. More or less, octane helps control the time of explosion as it enters your cylinder.

The manufacturer determines what octane your engine will run best on and that is what you should stick with, unless you have modified your engine. As mentioned previously, look at your owners manual and see what your particular model requires, don’t ask for opinions. Most U.S. gas stations sell fuel rated from 87-93 octane. Depending on the region, octane rating may vary.

WHO’S RON?

For example, in the case of the 1975 Mercedes 450SL, with a V8 and an 8:1 compression, Mercedes specifically calls for fuel with a minimum rating of RON 91 and that is exactly what you should use, no more, no less.

But what exactly is RON? RON is the european equivalent of the U.S. octane rating and is converted using the following formula: In this case, RON 91, multiplied by 0.95 giving you a minimum octane rating of 86.45 or 87 octane at the pump.

As you can see, your cool classic, in this case our oh so cool, ’75 Mercedes 450SL simply does not need high octane gasoline. Remember, running higher octane levels then the manufacture designed the engine for will serve no purpose other than to fund your gasoline retailer and your favorite oil company.

In the event your engine should start to ping or knock, you should not automatically jump to conclusions that you have an octane problem. Instead, check all of the following which can cause knocking: Carbon buildup in the cylinders, Timing that is too advanced, Engine overheating and lean fuel mixture can all cause knocking.

IT’S ALL IN THE BURN

Should you discover that your engine does require higher octane than you can get at the pump, there are options, but one that really does the job well. After extensive research on dozens of octane boosters and experimenting on numerous brands, Torco Racing Fuels, Accelerator stood out among the crowd. The Torco Accelerator was tested on a Rolls-Royce 6.25L V8 that requires 100 octane fuel and on the first tank, sufficiently increased the octane when added to 93 octane at the pump. While the owners manual and the placard mounted above the gas cap states “100 Octane Fuel” it has been observed that the engine does not ping or knock with a 97-98 octane mixture.

Unfortunately many chemicals, additives, etc., do not live up to their claims, despite the awe inspiring stories. In this particular case, the reason the Torco Accelerator works is simple. It is nothing more than enhanced racing fuel in a can.

As with any new product you are not familiar with, read all instructions carefully, following all manufactures directions for proper use/application and READ YOUR OWNERS MANUAL. It takes the guess work out of everything.

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Written by :
West Kenyon

West Kenyon is a Multi-Media Design Consultant and automotive enthusiast. Cars in his collection include a 1956 Austin FX3-D, better known as a London Taxi, a 1965 Rolls-Royce Phantom V, and a 1975 450SL and 1981 240D by none other than Mercedes-Benz. West said, “owning one or a number of vintage cars is often an expensive proposition", which is why he does the majority of mechanical and interior work/restoration himself. West added, “not only does it save a significant amount of money to do the work yourself, it also provides full opportunity to know the job is being done with excellence and allows for an unprecedented appreciation and knowledge of the car.” For FCPEuro, West will focus on providing in-depth information on both the Mercedes-Benz R107, 450SL, D-Jetronic version and the W123, 240D. Glücklich Autofahren! (Happy Motoring)


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