Value of "high mileage" synthetic automotive oils vs. regular automotive oils 1

[Tunalover]

I've heard so many different opinions on this that I don't know what to think. The "high mileage" synthetic oils, used on high mileage cars, it MUCH more expensive than regular motor oils. Is it a waste of money? I was hoping to snag a tribologist or two with this thread to give the facts.

Tunalover

 

[romke]

synthetic oils are more expensive then regular mineral oils for two reasons: the base fluids used in synthetic oils are subjected to longer and more complicated processing then standard base oils and that makes them more expensive, the other reason is marketing: buying something that is "newer and better" always comes at a premium...

from a pure technical point of view the synthetic products are "better" in a number of areas: better cold flow properties, so after a cold start all the engine parts that need oil are served sooner. They also can withstand high temperatures better, which means that they do not deteriorate (oxidize) as fast as standard oils, which means they can be used longer or can be used in engines that have parts that run at very high temperatures where standard oils fail to offer the protection needed. Another notable difference is that because synthetic oils usually contain less of the complex molecules that are used to modify the viscosity-temperature characteristics (viscosity index improvers) they are not as prone to temporarily loose part of their viscosity in high temperature high shear situations as can occur in the valve train areas of modern engines. Because they are less susceptible to temporary viscosity loss they can also be thinner, which can make a small contribution to lowering fuel consumption, especially when the engine is used for commuting traffic.

for a number of modern cars with extended oil intervals use of these new quality oils is a absolute necessity - standard oils do not meet the quality requirements for these designs.with other designs both synthetic and standard oils may be used - often with a notable difference in suggested oil change intervals.

thus, underlying the hyped marketing is a strong backing of relevant testing and specifications - these oils would not have been brought to the market if their was no technical need for their use.

 

[Tunalover]

romke-
Is there any value to use these oils in high-mileage vehicles?


Tunalover

 

[romke]

you mean: vehicles that already have covered a long distance? maybe there is when they are used for commuting, covering small distances at a time and thus not fully warm up (to get the oil up to the envisaged temperature can take about 20 minutes, much longer then the thermostatically controlled engine coolant). on the other hand: if it is a older vehicle it may well have worn a bit and using a lower viscosity synthetic engine oil may result in the need for more top up. you might also notice a somewhat lower oil pressure. that is no need for worrying though - the lower oil pressure only indicates that the oil pump has to generate less pressure to push the oil through the piping towards bearings and valve gear - there the pressure is build up hydrodynamically to values that can be a 100 times higher then the pressure in the supply lines.

you could put it this way: if synthetic oils had been available at the time the vehicle was designed, the manufacturer most likely would have chosen such a type of oil. if the vehicle is older, it may already have worn to such a extend that it only would cost a lot more, whereas the advantages mentioned will not be fully available due to the wear of the engine that already has taken place.

at very low starting temperatures it might still be worth it: it could make a difference in the sense that with a low viscosity oil the engine would start easily whereas with a conventional oil the cranking speed would be insufficient to get the engine to start at all.

 

[IRstuff]

"if synthetic oils had been available at the time the vehicle was designed, the manufacturer most likely would have chosen such a type of oil."

NOT, unless there were a serious demand for it, but since most people dump their cars after 3 yrs, it's irrelevant. Car manufacturers niggle over the cost of bolts being a few pennies more; do you really think that would put in something that costs twice as much without a big fight?

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[Tunalover]

romke:
When I say "high-mileage vehicle" I generally mean a vehicle with many miles on it, say, >200k, used for long trips (>100mi) as well as frequent, short-mileage trips (<15mi).



Tunalover

 

[romke]

@tunalover

it is true that manufacturers try to cut production costs. that may also result in using a oil that offers somewhat less protection to help running in and/or that may not be used as long as a synthetic oil that they recommend for the user afterwards.

there is however a clear tendency to use better quality oils right from the start that can be left in the engine for a longer period, especially with european manufacturers.

 

[Tunalover]

@romke What I'm trying to answer is whether I should be using the synthetic oils instead of regular oil in my Toyota with 215k miles on it. Is it worth the extra money? If I use the synthetic oil, can I extend the time between oil changes? My mechanic says that regular oil is fine (and more economical) as long as you change it every 3-5k miles.



Tunalover

 

[romke]

your car will have some wear if you clocked up 215k miles. using a thinner synthetic oil might lead to some oil consumption past seals, valve stems and piston rings, or may not, depending on the amount of wear that has occurred over time.

as far as oil change intervals are concerned you might extend to say 15 k miles.

whether that would lead to a saving is hard to say, since it depends both on top up needed and the prices of standard and synthetic oil.

toyota engines usually are designed in such a way that they can function quite well with very little wear on rather cheap oils - a deliberate choice because a lot of the cars are sold in african and asian countries where high quality oils are not always available or people operating the cars will not buy high quality oils if they are available. thus, apart from more recent models that meet the latest emission regulations and where high quality oils are recommended, most likely those cars will neither need a synthetic oil nor will it give you any economical advantage.

 

[ccfowler]

tunalover,

You may want to consider lubricants specifically intended to be used in older or high-mileage vehicles. These are conventional oils with additives intended to help extend the useful life of old gaskets and seals. I've seen these from other sources, but the only one that I can remember at this moment is Valvoline. In general, I prefer to use or specify conventional lubricants unless there is some compelling reason to use a synthetic lubricant for the specific application.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.