Oil changes…if you drive 12-15,000 miles a year like most people, it seems like it’s time for another oil change every time you turn around. Why are oil changes such a big deal? Our technicians at Puyallup Goodyear would like to answer that question, and maybe a couple of others.
Q: What’s the recommended interval for oil changes?
A: At one time, oil changes were recommended at 3,000 mile intervals. Most manufacturers and auto repair techs now agree that a 3,000 mile interval is a little excessive. Today’s engines and motor oil formulations can easily go for 5-7,000 miles between oil changes with no problems. Always check your owner’s manual for manufacturer’s recommended intervals and motor oil grade. NOTE: these numbers apply to conventional, mineral-based motor oil.
Q: I keep hearing a lot about synthetic oil. Is synthetic motor oil really worth the extra cost?
A: The answer is an unequivocal yes. Synthetic oil formulations outperform conventional motor oil in every aspect – they lubricate better, aren’t as prone to carbon deposits and don’t break down as quickly. As a consequence, oil change intervals of 10-12,000 miles aren’t unusual with synthetics (always check manufacturer’s recommendations). The cost may be significantly more, but you won’t be doing it nearly as often either. That’s why almost every manufacturer now recommends synthetics for their new models.
Q: Do I have to stick with the same brand of motor oil forever?
A: No. That’s an old-wives’-tale that has circulated for years…that switching brands would cause a car to start burning oil. Truth is, that was a ploy to keep drivers loyal to the same brand! Any good grade of motor oil (not the store brand at the convenience store) will do an equally good job of lubricating and protecting an engine.
Q: I’ve heard that a switch from conventional to synthetic motor oil will make an engine start to leak. Is this true?
A: At one time, there was some validity to that. Older formulations of synthetic motor oil contained additives that could enable oil to make its way past gaskets and seals to cause leaks. Newer synthetics are formulated differently; lube shops, dealerships and others are no longer reporting leakage problems with newer synthetics.
Q: What’s the story on high-mileage motor oils?
A: Normal wear means somewhat looser tolerances on moving parts…not just engine parts, even things like door handles. When it comes to high-mileage motor oil, there’s two schools of thought. Some will advise a 75,000 mile threshold for making the switch to high-mileage oil, regardless of engine condition. Others recommend a switch at the first sign of leakage, or noise from lifters or other parts. High-mileage oils incorporate conditioners that can help gaskets and seals expand to stop leakage. In addition, their friction modifiers and viscosity additives keep high-mileage oils from breaking down and losing their lubricating properties.
Q: What do the number designations on motor oil mean?
A: Oil tends to thicken when cold and thin out when hot. The Society of Automotive Engineers (SAE) and other industry groups assign numbers that indicate the oil’s viscosity properties; the higher the number (as in, “SAE 40W”), the thicker the oil. A number like “10W-40” indicates a motor oil with multi-viscosity properties, which are achieved through oil additives. Little known fact: the W refers to “winter” and not “weight.”
Q: What happens if I don’t stick with a regular oil change schedule?
A: Putting off one oil change by 1000 miles won’t really do much harm. If you regularly fall into the habit, though, the carbon and acidic byproducts from the combustion process will start to build up in your motor oil. The particles will be suspended in the oil so that they can be trapped by the paper element of the oil filter, but eventually the filter will become saturated and carbon will start to build up as sludgy deposits on moving parts like bearings and the valve train. This isn’t something you want to see happen – it can shorten engine life drastically.
Q: The oil dipstick has a margin for proper fill level. What happens if a crankcase is overfilled?
A: Well, there’s a good reason why your dipstick has “Do Not Overfill” stamped on it. In a too-full crankcase, the crankshaft will dip down into the oil and whip it into a froth. When oil is foamy, with more air than oil, the oil pump can no longer work efficiently. Oil pressure falls off, oil doesn’t make it to crucial moving parts and major engine damage occurs. In addition, it’s possible for enough oil to make it into the combustions chambers to cause “hydrolock,” a condition where the pistons try to compress a liquid. Liquids, of course, can’t be compressed like a fuel/air mixture, and what happens is the pistons’ connecting rods break or bend, resulting in a catastrophic engine failure.
We know this isn’t exactly an exhaustive Q and A on motor oil and how it works, but we hope it can at least answer some of your questions. Have you had a look at your odometer (or your oil) lately? Is it time for an oil change again? Give us a call at Sea Tac Tire & Auto Tech and let us get you taken care of and back on your way again!