Can Synthetic Engine Oil Help Prevent Intake Carbon Deposits?
Direct Injection Turbo Engine Carbon Issues – Sponsored By Valvoline
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This video about car engine oil will be focusing on three questions:
1. Why do modern engines have carbon build up?
2. How can engine oil help prevent carbon deposits?
3. How do you know if the oil you’re buying helps prevent carbon build up?
Unlike many older engines, modern engines are trending towards turbocharged, downsized, direct injection engines for efficiency benefits. But these changes now create unique challenges for newer engines, which have higher internal pressures and temperatures, and a lack of port injectors. Looking at the intake valve on a gasoline engine with direct injection, we need to think about all of the different ways that contaminants can contact these intake valves.
1. First off, blow-by from combustion can reach the intake valves through the positive crankcase ventilation system, which prevents the crankcase pressure from getting too high.
2. The PCV system also means that as the lighter part of the engine oil evaporates, it can pass by the intake valves.
3. You can also have exhaust gases routed back to the intake valves, through an exhaust gas recirculation system, typically used for emissions purposes, which carry combustion contaminants. Remaining exhaust gases can also contact the intake valve from inside the combustion chamber when the intake valve opens.
4. Finally, engine oil can leak down the valve guides and contact the intake valves, especially as oil viscosities continue to become thinner for efficiency purposes.
In direct injection engines, the oil itself is really all you’ve got to actively protect your intake valves. The oil itself is composed of about 80% base oil, and 20% additives, both of which play a role in fighting carbon deposits. From a base oil standpoint, you don’t want molecules that break down or evaporate with heat, but at the same time they should have good flow characteristics at low temperatures. This means you don’t want overly large or overly small molecules, molecules that aren’t fully saturated with hydrogen or overly long straight chain molecules. The wrong molecular structure can break down with heat and form deposit precursors. These precursors will attach to intake valves, pistons, and cylinder walls, and form deposits. This is where the additives come in, particularly detergents and dispersants.
Detergents have a hydrocarbon tale and a polar head, usually a metal.This means one end, the polar head, likes to bond to metallic surfaces, while the other end deflects deposits and prevents them from bonding to the metal surface. If precursors can’t contact the metal surfaces, they can’t form deposits.
Now dispersants also have a hydrocarbon tale and a polar head, however the tale is a bit longer than detergents, and the polar head isn’t quite as strong. The hydrocarbon tale likes oil, while the polar head likes water, metals, and contaminants, basically the things you don’t want. So as a deposit precursor is floating around in the oil, the dispersants will attach to it, keeping the contaminant suspended so it doesn’t attach to metal surfaces. From there it can either be filtered out as it passes through the oil filter, or kept suspended until you change the oil.
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