Bus and Motor Coach Library

Basic Maintenance – Some Fundamentals 

Author – Tom Olszewski, ExxonMobil (2001)

Tom Olszewski is a recognized lubricant technology expert.  He has spoken before industry association panels and has published several technical articles.  He is based at ExxonMobil Lubricants & Petroleum Specialties Company headquartered in Fairfax VA. 
As Group Leader for automotive and heavy-duty products at ExxonMobil, Olszewski works with research staff and additive suppliers to specify, formulate, and field test finished lubricants.  He works with ExxonMobil customers on new product development, fleet operations, maintenance issues, and special lubricant requirements.  He also assists with training new ExxonMobil technical sales engineers.

A lot is published about "Best Maintenance Practices".  There is no doubt that preventive maintenance is the key to keeping your fleet vehicles road ready, reducing your vehicle operating, maintenance, and replacement costs, and improving your fleet's bottom line.

Here, we'd like to address some of the areas often overlooked as well as common mistakes made in fleet maintenance practices:


It is important that there is no "leaks" between the air filter and the engine and that the filter is changed at proper intervals.  Air cleaner elements should be changed based on intake restriction not necessarily at regular intervals.  Each time the air cleaner element is changed, there is potential for dirt to enter the engine.  Premature changes often result in dirt entering the engine.  Small amounts of dirt cause accelerated engine wear and may wear out the engine.  In used oil analysis, dirt will show up as high silicon content.

Starting aids.             

If you use Ether as a starting aid, remember you're dealing with an "explosive" that can seriously damage your engine.  And never let a starting aid substitute for the correct viscosity oil.  An engine that starts despite the sluggishness of the oil will receive almost no lubricant at critical points for several minutes after start-up.  This is when significant engine wear can occur.  For frequent low temperature start-up, lower viscosity oil may be needed.  Consult your owner's manual and talk with your oil supplier about their recommendations.

Cooling system. 

            Keep a close watch on your cooling system.  Some trucking experts believe that 50 percent of all premature engine failures begin with a problem in the cooling system.  Check cooling fans for wear.  An intermittent squeal often signals a loose belt.  Choose your antifreeze/coolants and supplemental coolant inhibitor wisely.  Coolant leaks deplete not only antifreeze but also supplemental coolant inhibitor concentration.  Manufacturers' recommendations should be consulted at all times.  Coolant leaks into the engine oil may be found using oil analysis.  Elevated levels of elements such as sodium, potassium, boron, and silicon may indicate a coolant leak.

Fluid ratios.             

Less can be more.  Don't increase the ratio of antifreeze/coolant to water above 70:30, expecting that a "stronger" mix will do a better job.  It won't.  For optimum freeze protection always follow the manufacturer's (engine or antifreeze manufacturer's) recommended ratios.


            If you're using a turbocharger without a separate oil circulator system, let the engine idle a few minutes before shut down so the oil can cool down; otherwise it may "cook," shortening its useful life and forming harmful deposits on the turbocharger bearings.  Using high quality engine oil with excellent detergency and anti-oxidants is also an important consideration.

Oil filter.             

Changing oil without changing the oil filter is poor practice.  The useful filter life has been reduced during the first drain, and may fail during the second, leaving your engine unprotected.  It is important to use a high quality oil filter.  For extended drain applications, it is important to use a synthetic media type filter.

Oil change. 

            If you're ready for an oil change, don't pull the plug on a cold winter's morning.  A lot of oil and sludge will stubbornly cling to the cylinder walls and as much as two quarts of oil may remain in the engine.  Oil changes are always more effective when the oil is warm and flows freely.  This also holds true for gear oil, transmission, and hydraulic fluid.


If you're concerned about fuel costs, try cutting down on your idling time.  In most ambient conditions, engines will retain enough temperature to restart after sitting a few hours.  Anything beyond idling for a few minutes after a long run, wastes fuel, may reduce the life of your engine oil and promote corrosive wear in the liner and bearings.  Why?  Because engine temperature is so much lower when you're idling, and water vapor can condense in the crankcase and produce corrosive sulfurous acid.  With the right choice of engine oil to help your cold weather starts, most of that idling can be avoided.  Idling can also lead to high levels of soot in your oil, which can shorten oil life and thicken oil prematurely.


Supplementary additives (top treats) - even those sold under popular brand names - are an expense that you can live without.  If you've made a good choice in engine oils, you don't need any other products in your crankcase.  In fact, supplemental additives may destabilize your engine oil and create problems.

Fluid levels.             

Maintain proper fluid levels.  Running an engine while the oil level is too low can cause engine damage.  Too high an oil level often results in rapid oil loss out the breather.  Maintain oil levels between the high and low level marked on the dipstick.


Try to fill your fuel tank at the end of the day, rather than first thing in the morning.  This helps to prevent condensation from forming in the tank overnight; condensation often leads to a build-up of water and sludge.