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Synthetic Oil Myths

Synthetic oil myths and facts

There are lots of synthetic oil myths, but here are the facts about synthetic oil

image of bottle of valvoline synthetic oil

#1 It’s a synthetic oil myth that you must perform an engine flush before switching to synthetic

NO! The screwy rationale for this myth is that since synthetic oil contains more detergents than conventional oil, it will immediately dislodge the sludge in your engine and destroy it.

Synthetic oil does have more detergent than conventional oil. However, synthetic oils also contain higher levels of dispersant additive. The dispersant is what keeps the dirt in suspension and carries it off to the filter. In other words, synthetic oil doesn’t dissolve buildup and then just drop it at the bottom of the engine.

The myth also assumes that you have sludge buildup in the first place. If you’ve neglected normal oil changes, you may have sludge. But if you change your oil on time, you won’t have sludge.

If you’ve been maintaining your vehicle according to the manufacturer’s recommendations, flushing your engine is a complete waste of time and money. If you’ve neglected your engine, flushing it is the WORST thing you could do. See my article “Engine Flush=Wallet Flush” to see what kind of catastrophic damage you can do to a sludged-up engine by flushing it.

The bottom line is this: DON’T flush a well-maintained engine before switching to synthetic, and DON’T flush a poorly maintained engine in the hope that you can bring it back from hell.

#2 Switching to synthetic will cause my engine to leak — NOPE

This was true when synthetic motor oils first came out. Those oils were designed for racing. Racing oils don’t need seal conditioners, dispersants, or detergent additives because they’re changed after every race. But when people used those racing oils in their daily drivers, the lack of seal conditioners caused gaskets and seals to leak.

Seal conditioners soften the seals and actually make them swell. If an aged engine seal returned to its hardened state, it can leak. But since synthetic oils flow easier when cold, that only compounded the problem. The engine parts on a cold engine contract. Add in hardened seals and a thinner oil and guess what—you get leaks.
But today’s synthetic oils have the same seal conditioners as conventional oil. So if someone tells you that switching to synthetic will cause your engine to leak, tell them their information is outdated by about 25 years.

#3 It’s a synthetic oil myth that you can automatically go longer between oil changes if you switch to synthetic

Synthetic oil can go longer between oil changes in an engine that’s designed for synthetic oil. Those engines are designed differently and have tighter tolerances for blow-by and wear.

The only safe way to extend oil changes when using synthetic is to get the oil lab tested to determine how well it’s performing in YOUR engine. So you can test the oil every 5,000 miles and see how the additives are holding up over time. But you’ll spend $25 on each test. In the meantime, the viscosity improvers, anti-oxidant, anti-foaming, friction modifiers, and dispersants are constantly wearing out. Even if the lab results show little metal wear, worn oil reduces gas mileage and increases engine emissions.

Bottom line. The only way to reliably run extended drain intervals is to test your oil on a regular basis. That will cost you far more than just changing it according to the manufacturer’s recommendations.

#4 Once you switch to synthetic, you can’t go back to traditional oil

There is NO truth to this rumor. None. Nadda. Zip. It’s a myth—plain and simple. Go ahead and switch back and forth as much as you want.

#5 Since synthetic oils flow better at cold temps, you can bump up to the next higher viscosity to provide better engine protection

We all know that you want a thicker oil to protect your engine at higher temps. So, if the manufacturer recommends 5W-30, should you move up to 10W-50 if you’re running synthetic? NOPE. It’s true that synthetic 5W oil flows better than conventional 5W oil. But it’s not true that a 10W synthetic flows as well as a 5W conventional. And that thicker oil can really screw up variable valve timing mechanisms—even resulting in a Check Engine light. Trust me, the manufacturers have done a lot of research on this. If they want you to use 5W-30, don’t think you can outsmart them.

For more information on synthetic oil, see this post

© 2012 Rick Muscoplat


Posted on by Rick Muscoplat

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