AOL Autos Repair Blog

Tom,
I have a 2005 Hyundai and the book says to use 87octane middle-grade gas. What would happen if I use regular grade?
-Santa Monica, CA

Answer:
Over time a condition called "pre-ignition" or "engine knock" will occur. With this condition, when the fuel enters the engine it pre-ignites, which causes constant hammering of the tops of the pistons, cylinder head face, and valves. Eventually, major engine damage becomes evident and major repair becomes necessary. Your choice? Cheap gas or engine replacement. Don't be 'penny wise and pound foolish.'

Dear Tom,
Could you please explain the difference between synthetic oil and regular oil for a car? Is it safe to use synthetic oil? I drive a 2006 Mazda 6. Thank you.
-Monticello, VA

Answer:
Synthetic oil (though not impervious to) is highly resistant to viscosity breakdown from chemical contamination, heat, and friction inside the internal combustion engine. Viscosity breakdown is the loss of ability of the oil to lubricate an engine. This toughness is due to the chemical fortification of the base stock oil at formulation. Non-synthetic oil tends to break down more easily because it lacks this chemical fortification.