Many of us don't want to give up our fine older cars. We don't want to trade their reliability and ease of maintenance for today's inefficient icient and temperamental engines. We don't want to trade the solid comfort we now enjoy for the cramped confines of a little dodge-em car. Why drive a sardine can?
However, we who drive the fine older cars have a real problem. Whether deliberately or not, "they" are driving our cars off the road. Engine problems are now endemic among American cars built between 1955 and 1974. The culprit is the gas we're sold today.
[quoteright]Our pre-1972 cars were built when the competitive efficiency of U.S. oil companies resulted in the highest octane gas in the world at very low prices. At a time when European and Japanese car manufacturers had to build engines for expensive gas of dubious quality, U.S. manufacturers made efficient engines that took advantage of the inexpensive high octane gas available here. American engines were the envy of manufacturers the world over.
But thanks to the paternalistic machinations of our governmant during the past 15 years, the quality (octane rating) of gas available in the U.S. has deteriorated. The high compression engine in an older car will not run satisfactorily on the unleaded gas you can buy today. You'll be asking for major engine work much sooner than should be required, and you may wind up junking your otherwise good old car. What can you do? A few definitions first, then sons suggestions.
Compression Ratio. This specifies how much the engine compresses the gas and air mixture before ignition. Ratios of 9.5:1 or higher are generally called "high compression." The 1965 Mustang 289 has a 10:1 compression ratio, and the 1968 Chrysler 440 has a 10.5:1. For comparison, the 1981 Honda Accord is only 8.8:1.
Octane Rating. This measures the ability of a gasoline to deliver power to the engine without "pinging," or detonating prematurely. The octane number posted on gas pumps today is a different measure from that used in 1965; 96 (average method) octane today is roughly equivalent to 100 (research) octane then.
Lead. Tetraethyl lead is a gasoline additive, disliked by the EPA. It serves two purposes in gasoline: it raises the octane rating, and it both lubricates and cushions the valves in the engine.
A high compression ratio requires high octane gas. If the octane rating is too low, the engine will "ping" when accelerating or under load, especially in hot weather. Pinging tells you that the valves and spark plugs are taking a beating. Exhaust emissions are increasing and the day you need an engine overhaul is rapidly getting closer. Even if you find an unleaded gas that eliminates "ping" in your car, you can expect an engine overhaul many thousands of miles earlier than if you were using the leaded formula your car was designed for. Before EPA, leaded gas had 3.0+ gm/gallon of lead; it now has as little as 0.5 gm/gallon, which is an absolute minimum for engine protection.
If you drive an older car with a high compression engine, the following hints will help you keep it running well with a minimum of repairs and a maximum time before an overhaul is required. However, they will not improve an already damaged engine or noticeably improve mileage.
1. Don't use unleaded premium gas. You will damage the valves.
2. Don't try to get by with leaded regular. Although the lead will help protect the valves, low octane pinging will damage them.
3. Don't use an oil additive; today's multiviscosity (e.g., 1OW-40) oils have all the ingredients needed.
4. Don't drive with worn or fouled spark plugs.
5. Don't retard the spark setting. Some mechanics recommend this, but it degrades performance and tends to foul the engine.
6. Switch to 92 octane leaded premium, such as Union Super 76 or Ashland. This is the highest octane leaded gas available today. It is usually adequate for a clean engine with a 10:1 ratio or lower. If you engine doesn't ping except rarely, you're in luck. You may not notice an improvement until after taking a 50 mile or longer nonstop trip at highway speed with the new gas.
7. If your engine still pings, mix 92 octane leaded premium with 90-91 octane unleaded premium from Mobil or Texaco. The mixture will be very scant on lead, but will have about 93 octane. The reason is another essay.
8. Ignore those who advise mixing unleaded premium with leaded regular. The resultant octane is too low and the lead content also is scant.
9. Have your engine overhauled and its compression reduced to run on leaded regular. This costs a fortune, and performance will still suffer.
10. Have a demand-type water injection system installed. This is an expensive modification to be approached with caution.
11. Do as I do. Follow suggestion #6 and add an octane booster. An octane booster is a specific kind of additive you can buy at auto parts stores. Available brands include Moroso, Vortex, and 104+. I use 104+ in my 1968 Chrysler 440 because Vortex must be premixed before it is put in the gas tank. 104+ costs $5-10 for a 12-ounce can, so it pays to shop around. I believe that use of an octane booster with today's leaded premium will help keep a high compression engine running much longer, delivering the kind of performance it was designed for.
If you pour a half can of 104+ into a nearly empty gas tank and fill with 92 octane leaded premium, the result should be adequate for lightfooted everyday driving. Although this can raise the cost of gas by 20 cents a gallon without noticeably improving mileage, you may save it back in repairs while increasing the enjoyment of your fine older car.
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