It is not generally realized that a large number of things enter into the economical use of gasoline. To get the most out of a gallon of gasoline all moving parts must work properly. This means proper lubrication. The brakes should not drag; each cylinder of the engine should fire properly; the clutch should not slip, and the carburetor should be in proper adjustment. It is not well to adjust the carburetor unless you are sure it is at fault. Excessive carbon in the cylinder causes a decided loss of power, due to back pressure on the piston, and the partial clogging of the muffler indirectly consumes extra gasoline. The importance of keeping the muffler free is not usually understood.
To insure each cylinder getting its proper power without waste, the engine should be driven with the spark lever advanced as far as possible without causing back pressure. The spark-plug gaps should be properly adjusted to insure a thorough ignition of the charge; the spark plugs should be kept clean to prevent the loss of a charge of gas through non-ignition, likewise the interrupter points, and the distributor should be kept clean and properly adjusted.
To use all the gas that is taken into the cylinder there should be no loss of compression through leaky valves, or weak valve springs, or poor gaskets on spark plugs or valve caps; and it is equally important that pet cocks, cylinder head, where there is one, and piston rings are tight, so that gas will not be wasted.
It is not safe to leave these things to the chauffeur and the garage man. The owner should learn himself how to make all these adjustments. If he does so he will find that his propelling machine will work better, and that he will not only have more use and pleasure out of it, but he will save a very appreciable part of the cost of up-keep.
CHAPTER XI
THINGS WHICH MAKE GAS BILLS HIGH
There are other things which affect the amount of gas consumed which need the attention of the automobile owner. One of the common things, mentioned in the preceding chapter, concerns the intake manifold, which has to do with the distribution of the gas mixture from the carburetor to the several cylinders. A leak at the carburetor side would prevent drawing into the manifold a sufficient supply of the mixture, so that the cylinders would be scantily supplied—perhaps one or more not supplied at all. Likewise air would be drawn into the manifold through the leak, and this would thin the mixture coming from the carburetor. As the mixture in the cylinders would be thin it would not compress properly, the firing pressure would be poor, the mixture would fire badly or not at all, and the power would be lessened.
The natural thing to do when the misfiring is noticed is to open the spray or needle valve, admitting more gasoline to the mixing chamber and making a higher consumption with no gain in power. The proper thing to do, however, is to look for a leak in the manifold.
If the leak is on the cylinder side of the manifold, it might be at one or all of the cylinders. The result would be the same as in the case just cited, a poor supply of the mixture, or some of the cylinders might be properly supplied and work all right, while others might be short of the mixture and might not fire at all. The loss might be sufficient to affect seriously the power and lessen the speed of the car.
The manifold ought not to become loosened in the ordinary use of the car. There have been cases where vibration has done it, but the usual trouble is where the manifold has been removed for some purpose and improperly replaced. Copper and asbestos gaskets ordinarily are used, and these may be dented or jammed out of shape so that the joint is not tight, or there might have been no shellac handy, or the bolts may not have been tightened enough. Whatever the reason, the leak makes a weak mixture, and the first thought of the chauffeur or the average garage man is to increase the gasoline at the spray nozzle of the carburetor to make the mixture of the right proportion to fire. On account of the mixture being made in the intake manifold, instead of the carburetor, as it should be, the work is not efficiently done and gasoline is wasted, the result being the increase of the expense account.
One of the most common causes of gas loss is from leaky supply pipes. Where there is a solid pipe from tank to carburetor the only leak, barring a break or perforation of the pipe, would be at the connection with the tank or the carburetor. Vibration might cause the joints to loosen, though if they are put together properly with shellac, soap or some equivalent, and are thoroughly tightened, there ought not to be any loosening. It is needless, but how often we see a car dripping gasoline at considerable loss. It is also dangerous, for a stray flame or spark may ignite the gas.