Is Synthetic Motor Oil Bad For Old Cars?

hello everyone and welcome in this video we are continuing the series sponsored by mobile one where they have provided me with access to their engineering teams to answer the many questions that surround motor oil in this video we're tackling a heavily debated subject whether or not you can use synthetic oils in old cars so we're going to be answering the following questions can you use synthetic oils in old cars can synthetic oils cause leaks in old cars if your car is consuming a lot of oil should you use a thicker oil and when should you consider using a high mileage oil lots to work through so first off let's start with the basics can you use synthetic oils in older cars and older engines the simple answer is yes absolutely there's no issue using synthetic oils in older cars and we'll get into where the idea that you couldn't originated but whether your car is 30 years old or a classic there is often a synthetic product available for it i think the easiest way of knowing this is simply looking at manufacturer recommendations porsche has factory filled with mobil one synthetic zero w40 since 1996 but if you go back further to porsche classic cars you start to get cars with larger engine clearances that require thicker oils porsche approves a mobile one synthetic 5w50 and 15w50 in their classic cars requiring a 50 weight oil and synthetic oils are nothing new they've been around for commercial use in the automotive industry since the 1970s so in my opinion the more interesting part of this discussion is where the idea came from that you can't use synthetics in older cars ultimately it comes from bad experiences in the past some of the early synthetic motor oils were ester based and actually some engine seals are ester based and there's a compatibility there esters can cause swelling of engine seals and a little bit can actually be a good thing but if the ester concentration of the oil is too high you could see excessive swelling of the seals a drop in the seal's hardness or a loss of tensile strength okay so think about what you want to happen inside of the engine you want the seal to maintain its properties regardless of what the engine is doing hot cold say you drop a seal into hot engine oil you don't want the seal to get brittle or lose strength and with some early synthetic motor oils likely with base stock formulations that are no longer used today that's what happened the oil wasn't super compatible with the engine seals so you found oil leaking all over your driveway so how do we know modern synthetic oils won't damage engine seals well there's all kinds of testing to ensure that doesn't happen which is why it's no longer a problem for example mobil 1 synthetic was commercially introduced to the united states in 1974. obviously at the time there were far fewer industry requirements today if you look at the back of a bottle of oil you'll see an api certification an ilsac certification and various manufacturer certifications like gm's dexos these certifications have extensive testing and they'll include seal compatibility tests to ensure that what's inside the bottle is actually compatible with the seals used in engines all of this is to say that if an oil has the proper certifications you don't have to worry about seal compatibility with your engine and running a synthetic is no problem okay so what about this idea that's often perpetuated that synthetic oils have more cleaning power and will remove built up sludge and gunk within your engine exposing leaks and causing your engine to now leak oil now this is the absolute wrong approach towards the longevity of an engine so it's true that synthetics can have higher concentrations of dispersants and detergents and other cleaning elements but cleaning your engine is never a bad thing keeping an engine clean is never a bad thing certainly if you have sludge or gunk building up this is bad for your engine that sludge can plug up oil drain holes which lead to more sludge forming on the top end of your engine which then gets too hot and eventually fails if your engine has a leak that's obviously a problem and there's probably a failed seal however sludge and gunk building up around that seal is not a solution it's just another problem using sludge as the solution would mean causing your engine to fail sooner so that it doesn't leak oil that's obviously a bit backwards okay now what about old engines that are burning or consuming a lot of oil in this case should you consider using a thicker oil and actually it might not be a bad idea as a general rule you should always use the viscosity your car manufacturer recommends but as we all know engines don't last forever where happens and as you have wear occurring this can change the clearances within an engine for example let's say you have an old car and there's quite a lot of miles on it and while you're sitting at idle when you have a relatively low oil pressure the oil pressure light comes on or maybe flickers well in this case the oil may have originally been fine for maintaining oil pressure but as the clearance is within the engine increased now there's more space and the oil might be too thin to maintain pressure in the wider areas so using a thicker oil could prolong the life of the engine i think the important thing here is understanding that you shouldn't proactively switch to a thicker grade oil without any signs that your engine is old or worn bumping up an oil grade should be thought of as a last-ditch effort of prolonging the life of an engine that's clearly on its way out the thicker oil could help but it's not going to change the fact that your engine has significant wear higher viscosity oils also tend to have a lower volatility which means less of the oil burns off over time now as far as an engine that's leaking oil so you have spots on your driveway well changing to a thicker oil isn't addressing the problem that seals have failed and it likely won't help if there's a passageway or seal that oil is leaking through the difference in viscosity between say a 5w20 and a 5w30 at operating temperature is too small to actually make a difference in whether or not oil can slip by the leak is going to continue to leak again the problem here is a failed seal not that your oil is the wrong viscosity and this discussion on leaks leads to our final question when should you consider using a high mileage oil so high mileage oils seek to be a solution for engines that have started to wear and might be burning excessive oil or leaking oil there are a couple of differences versus a standard synthetic oil high mileage oils have a seal swelling agent which serves the purpose of reconditioning engine seals so if you think about a seal over time the seal can harden shrink and lose its elasticity the swelling agent is designed to recondition that seal so that less oil makes its way past now this doesn't mean the seal is permanently fixed right if your engine's issue is a broken seal well then the ultimate fix is replacing that seal but a high mileage oil can help prolong the seal's useful life if it has started to deteriorate it can be useful to try and swell an old seal back to its original state but obviously you wouldn't want to proactively try to swell a brand new seal that said if for some reason you were to start using a high mileage oil early it's not going to harm your engine as long as you can see it meets all of the required industry tests a common spot where a failed seal can cause you to burn a lot of engine oil are the valve stem seals so these seals prevent oil from within the cylinder head from entering your intake manifold if the seal deteriorates or fails oil will drip down onto the intake valves and move into the combustion chamber along with the intake air and burn up in the engine or if the oil leaks down the exhaust valves the oil will exit with the flow of exhaust gases another difference of high mileage oils is they may use a base oil with a heavier mixture this slightly higher viscosity means the oil has less volatility and less of it turns into a gas burning within your engine again it's important to understand why your engine is burning more oil than usual for example it could be from oil leaking down the valve guides it could be that the surface between the piston rings and the cylinder liner is too smooth and the cross hatching is worn down and no longer holds oil it could be from oil mist in the crank case specifically the more volatile compounds which end up burning off through the crankcase ventilation system quite simply old engines will start to experience problems a high mileage engine oil isn't going to reverse engine wear but it can help recondition engine seals and help cut down on oil consumption so to summarize yes you can use synthetic oils in old engines and it's not going to cause a leak like some of the early synthetic products on the market yes bumping up a viscosity grade could help a worn engine restore oil pressure and yes switching to a high mileage oil can help reduce oil consumption in an aging engine now as a quick little bonus fact it's often stated that rotary engines cannot use synthetic oil because they'll create carbon deposits i asked mobil1 about this and they suggested the original logic behind this is likely linked to a bad experience when synthetics were first introduced rotary engines spray oil directly into the combustion chamber to lubricate the apex seals and this oil is eventually burned off but whether it's a synthetic or a conventional oil you're spraying oil which is made up of hydrocarbons chains of hydrogen and carbon atoms directly into the combustion chamber either way you're going to be burning this oil so if a synthetic were to cause carbon buildup well a conventional oil would as well synthetics offer a lot of advantages however which is why you'll see them used in motorsport applications that are still using rotary engines sometimes even removing the oil metering and instead pre-mixing specific oils with the fuel so a big thank you to mobil1 for sponsoring this video and providing access to their engineering teams mobil1 synthetic can be found at a wide variety of retailers and service stations near you if you have any questions or comments of course feel free to leave them below thank you all so much for watching

Channel: Engineering Explained

Views: 982,651

Rating: 4.912746 out of 5

Keywords: synthetic vs conventional, synthetic oil, synthetic motor oil, motor oil, mobil 1, mobil 1 synthetic, high mileage oil, engineering explained, full synthetic, old car

Id: pPFSR-2lhxY

Length: 10min 39sec (639 seconds)

Published: Wed Sep 23 2020