Know the Fluids Under Your Hood

Phil Ramsey

Did you know that there are eight types of fluids under the hood of your car? If you haven’t already remembered what they are, at the end of this article I will name them. I have written about most of them in previous columns. But it occurred to me that not much has been written about the one we use the most - gasoline, or Petrol, for our European and Latin American friends.

Gas is the one fluid we are the most selective with at the point of purchase. People will drive for miles on a trip with a low fuel tank to find a better price. Brand loyalty to the major manufacturers, based on customer confidence in that particular company, has been falling for the past three decades as a result of the gas crisis of 1979. Back in those days of long lines at the pumps, just being able to purchase any gas was an achievement.

Gas has changed the cars we drive. Emissions laws have changed the gas we purchase. Consider that cars manufactured in the United States since 1975 have mandated catalytic converters on them. They must burn unleaded gasoline or the converter will plug and choke the car. Leaded gasoline was allowed to be sold until 1986 to cover those cars that were made prior to 1975. At that point, gasoline additive development had progressed to the point that older cars could burn unleaded gas. Leaded gas was banned in the United States after that.

The lead was added, in part, to raise the octane value of the gasoline, but octane values have not fallen with the removal of the lead. To accomplish this, refining techniques had to be modified to keep the octane standards that millions of cars on the road required. Gasoline is becoming a blended product designed to meet low-sulphur antismog requirements, as much as performance requirements based on weather conditions.

Political and market factors have changed the marketing of the product. My father owned a couple of gas stations during the 1950s and 1960s. We sold two kinds of gasoline, regular and premium; and two kinds of oil, detergent and nondetergent. Our gas had a substance: ethyl, a copyright brand and a corporation name, which was tetra-ethyl lead. It was placed there to artificially raise the octane rating of the gas, and it also lubricated the valve seats in the combustion chamber.

Back then, most anyone who worked in a gas station could perform general mechanical work on cars, fixing flats and servicing as needed. Those mechanics checked the fluid levels under the hood with every fill-up, offering free advice about the care of your car and its under-the-hood needs. But that, to borrow a phrase, is a day gone with the wind.

Since 1975, it is illegal to sell gas with lead in it. So now we have regular and premium, both unleaded gasoline. Gasoline is sold at convenience stores and mass outlets with little windows. Most oil is now changed at a specialty shop - same with flat tires. No one checks fluid levels under the hood anymore. Next time you are at one of those gasoline stores with two dozen pumps and the little window, stop and look around; you will not see a single hood open. This is great for mechanic shops, but bad for the customer who thinks he is saving a few cents on his gasoline purchase.

The gasoline and its delivery to the combustion chamber have changed dramatically in the last 30 years. Beyond regular and premium, the most familiar characteristic of gasoline is its octane number. Gasoline is the preferred fuel in cars during the last century.

The original combustion engine, invented by Nicklaus Otto in 1877, ran on alcohol, not gasoline. Henry Ford was a proponent of alcohol fuel and backed his beliefs by manufacturing the Model A from 1928 to 1931 to run on either gasoline or alcohol. Even though alcohol has a higher octane number than gasoline, is renewable, and burns absolutely clean, gasoline won out because it was cheaper. Today, however, both fuels are approaching the same cost, and alcohol has all of those other wonderful properties.

We do not want gasoline to knock or explode in the combustion chamber, but rather to burn smoothly over a few milliseconds. Its power can be applied in an even stroke on the piston, without a hammer or knock. Gasoline’s ability to resist detonation is measured by its octane number. The higher the octane number, the less likely the engine is to knock.

All gasoline is a blend of several refined crude oil components. Asphalt-based stocks of crude are blended with paraffin-based stocks. Chemicals, like the lead of the past, are added to keep the octane number within the advertised range. Gasoline is now blended to regional weather predictions, and some cities have special blends mandated by their EPA air quality readings.

Ethanol is a renewable resource with great emission properties. Ethanol is now blended into gasoline for emission and economic reasons. Henry Ford preferred ethanol over petroleum-based fuels. In an interview with the New York Times in 1925, he pointed out that ethanol had better octane ratings than the gas of his day, and that one acre of potatoes could produce, in one year, the fuel necessary to drive the machinery to grow that field for the next 100 years.

Fuel delivery has changed since my oil-drinking days (see the article “New Meaning to Oil Consumer” in Machinery Lubrication magazine, May-June 2001). Gasoline was vaporized in a carburetor, delivered by a mechanical pump and held in a tank vented to the air.

Today’s gasoline is different, the tanks are different, the carburetors are gone and the pumps are electric. The first in-tank electric fuel pump on a production car was on a 1975 Buick Riviera. When I realized that we had an electric motor sitting in a tank of gasoline - allegedly to keep the motor cool - I kept waiting to hear about explosions all over the country. Luckily I was wrong. The biggest problem with electric fuel pumps is that a fair number of people drove with their tanks half-full or less. The pumps were not cooled according to design and had to be replaced prematurely.

Water from condensate used to be a big problem. Carbureted cars would collect the water in the metering jets and shut down, or sputter and run poorly. Because cars now have fuel injectors instead of carburetors, it is no longer a big problem if a little water - say one to two percent - gets in the tank. In contrast, computer-controlled fuel-injected cars will merrily roll along most of the time, with the driver unaware of his contaminated tank.

The ability to alter combustion timing and fuel spray volumes, a feature of the later model fuel-injected cars, has made it easy to introduce ethanol into fuel blends today. In many cases, simply reprogramming the chip can provide the ability to burn pure alcohol. Henry Ford achieved this ability to burn either fuel in the same engine, without computerized fuel injection more than 70 years ago.

Automotive tip for the month: It is better to have a full tank of gasoline than a half-full one. The pump will last longer, thus preventing expensive repairs. Changing the fuel filter as part of your 15,000-mile service should help extend fuel pump life. The fuel filter is often located under the car near the fuel tank, and the old adage “out of sight out of mind” prevails. Change it every 15,000 miles please.

I said eight fluids were under the hood; do you remember all of them? Gasoline, motor oil, transmission fluid, power steering fluid, coolant, brake fluid, wiper fluid and air conditioning refrigerant (freon). The refrigerant’s accompanying oil can be number nine. Please see the related article “Replace or Convert?” in Machinery Lubrication magazine, March-April 2001.

Keep the gas tank full, and check under the hood.

Vehicle Fluids

For those of us who work and shop close to home, methanol may be an invisible assassin to our car engines. Under “short haul” driving conditions, fuel and water accumulate at a much higher rate with the use of methanol than with the use of gasoline. Testing conducted by General Motors Research Laboratories1 shows some of the drawbacks associated with the use of methanol as a fuel source.

  1. Methanol steam - Under test conditions, the methanol fuel accumulated in the crankcase of the test engine at nearly three to one vs. gasoline accumulation. Given the single boiling point for methanol vs. a sliding boiling point for gasoline, the methanol boils rapidly off of the crankcase via whatever means is possible once the oil sump temperature exceeds the methanol boiling point.
  2. Build-up of water in the crankcase - Because of differences in the energy content of the fuels, methanol produces twice the amount of water upon combustion as gasoline. Under the right circumstances, this could raise the level of fluid in the crankcase to a point high enough to cause churning and aeration of the fluid.

Engine wear increased appreciably as well in the methanol-powered engine during the test. Lead, iron, aluminum, chromium and copper were measured, as noted below, and found to increase between three to five times over the rate of wear for gasoline-powered engines.

The contamination issue seems to be self-correcting though. A single trip of sufficient duration to force the crankcase temperature to exceed 100ºC for at least one minute was enough to burn off the accumulated fuel and water contaminants in the methanol-powered engine.

While the test did not completely attribute the difference in wear metals increase to the contaminants, a general understanding of dynamic loading and the impact of that contamination suggests that there is a reasonable correlation.

Schwartz, S., Smolenski, D. and Clark, S. “Entry and Retention of Methanol Fuel in Engine Oil.” General Motors Research Laboratories research publication GMR-6092 FL-858. Warren, MI: February 1988.

Subscribe to Machinery Lubrication

About the Author