Has a majority opinion been reached regarding synthetic vs. "traditional" oil?

There is complete consensus on most Synthetic oils having much longer life than conventional oils. There is a lot of debate whether this matters at all for the very short oil change intervals called out in most US autos. Specifically, a properly formulated synthetic (not just any synthetic) can routinely last 25,000 miles whereas a conventional oil will rarely last that long.

So if the concern is the engine life and wear, you change at the manufacturer's stated interval, and you use the specified oil weight, then it makes little difference between synthetic and conventional. (However, extreme conditions of cold can make a difference if you are in a really cold climate.)

I'm at the other end of the spectrum. I don't want to waste oil. So I use a high grade synthetic, do oil sampling at around 15k miles to 25k miles, and change the oil based once the sampling indicators showing any impending degradation. Note that sampling checks BOTH the oil and the engine, so I know if I have a lubrication problem OR an engine wear problem.

 

I go to the Amsoil web site and order prepaid oil sampling kits. The kit is essentially a small bottle and a return pouch, along with some forms. A small sample pump and some tubing are needed in addition to the kit. I extract the oil out of the dipstick tube using the pump and tubing into the bottle. I mail the bottle in the prepaid pouch and wait two weeks to get the results via e-mail.

High grade means essentially the following:
1) The acid neutralization chemistry is enhanced to allow the oil to absorb a lot of engine contaminants.
2) There is a series of European oil ratings (ACEA) with an A1/B1 rating being very high grade and A5/B5 being very high grade. (The European ratings are more demanding than the US rating system. Long story of why.) That is the clearest definition of "high grade" I use.

 

Longevity of engine = following the bible faithfully: your owners' manual.


Either conventional or full synthetic oil MUST be changed! Exceeding (or ignoring) the manufacturers' recommended oil and filter change interval is asking for trouble.

If this is what your want, then have at it.

As already mentioned, synthetic does has better cold weather starting than conventional oil.

DBCassidy

 

My Civic is over 200k miles on a steady diet of bulk conventional 5W-30. Go look on Bob Is the Oil Guy or other forums and you'll see people who regularly change their conventional with a good filter are doing fine.

On the other hand synthetic does have some advantages and can run longer intervals safely. The downside of synthetic is that many dealers and shops seem to price a synthetic oil change like it is made of gold. $30 for a conventional change, and then $80 for synthetic. DIY, 5 quarts of Mobil 1 is just a few bucks more than good old Pennzoil yellow.

 

Yes

 

I prefer to tell what the tradeoffs are in this case and leave it to the readers to decide the course of action they choose.

For example, I want my engine to last far, far longer than the warranty. To do that requires me to go above and beyond what the owner's manual requires. This is one of those things. The 2001 engine is still running great, burning extremely little oil, and runs smooth. Another thing not in the owners manual is changing the transmission fluid at 60,000 miles. That has been shown to make a difference as well.

 

There must be a diminishing return along the way.

Care to guess what the curve looks like ? Or what oil change interval with a high quality oil is reasonable for say a 75% chance of the engine lasting 300/400/500k miles ?

As an aside, my WAG is that driver behavior is more important by far than exceeding the manufacturer recommended change interval. My engine lives most of it's life on road either off or running at 1500 - 2500 rpm, and rapid accelerations are rare.

 

FL does this sentence read the way you intended?

 

^^ The B designation is for diesel.

Many years ago an engineer posted his recommendations on a yahoo group for engine oil an filters. I still follow it, although I use 0W-20 for the later Gen Prius.

 

- Bob is the Oil Guy

 

All my experience with heavy machinery (e.g. Diesel engines, steam turbines, not cars) never depended upon an "interval" for lubrication change, it depended on sampling and inspections. Inspections often included checking magnets and filters for wear materials, color and even smell. Usually the limiting item on properly lubricated items were seals and intentional finite wear items such as piston rings. These items did have an inspection, overhaul, or change interval and there was a complete change out of lubrication fluid then, so we are not talking about making the lubrication last for crazy long periods. Obviously the approach for long component life is fundamentally different than how car components are handled. Cars are designed to last the warranty using the simplest maintenance approach feasible, change oil every XXX interval.

The key question about how long a car engine can last is very dependent on what is considered the End-Of-Life criteria. If no overhauling/tear down/ internal inspection of the engine is desired, then 500k miles might be achievable, but not guaranteed. However, if it dies, It's not going to be from the oil IF the oil is maintained at full lubrication specification (e.g. Total Base Number, Viscosity, Contamination from Water/Fuel/Oxides/etc.) Proper sampling checks all these things and a few others.

Now if overhauling and inspecting the engine is done, like on aircraft ICE engines, then 500k miles would be routine. A huge number of plane engines are crazy old, but extremely reliable and safe.

 

Correct me if I am wrong, I thought the oil analyses presented here on PC show that a 10k mile oil exchange interval using high quality oil are within spec.

 

Yes, but what I intended should be questioned. Glad you did. To be more precise:

The A5/B5 designation is the highest performance. The A1/B1 designation is high performance, but not to A5/B5 specifications. Both are excellent for Prius use. There was a time when 0W-20 was not available as A5/B5 so the best I could put in the 2010 Prius was A1/B1 for a while.

 

No, you are not wrong at all. Changing oil at the manufacturer's recommended interval definitely works. However, long life oils and sampling can achieve the same result or better at much longer intervals. That's what I practice. It results in a) much less oil going to waste, b) lower lifetime costs, and c) a positive check of both engine and oil health.

 

Yes, you are correct. If, you check with the latest owners' manual, you are fine. Problem is, when people think that using synthetic oil they can go 30, 40, 50K miles before changing the oil. UOA, will show the increase in various metals and contaminants in that same batch of oil. Build up of acids will also be seen. This build up does not go away until the current batch is exchanged with a fresh batch of oil and a new filter.

DBCassidy

 

Who here has said anything about actually going 50k miles on a single oil change? As far as the acids, that is why long life oils have very good acid neutralizers to keep the TBN at an optimum level. Using any extended interval should ALWAYS be supported with sampling to ensure no acid build up is occurring.

 

Has a majority opinion been reached regarding synthetic vs. "traditional" oil?

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Short Answer?​

No.



It's passionately debated, and when you read fiery 10,000 word posts on the subject you get to discover the difference between 'data' and 'fact'.
It's a lot like trying to discover whether or not caffeine REALLY IS is good for you or bad for you. My theory is even-year good/odd-year bad....or maybe whether or not a hospital needs a research grant...but I digress.....


Here's the thing.
Most cars don't go to the automotive afterlife from broken engines, and even an abused car with semi-occasional oil changes (like rental cars, fleet vehicles, etc....) will pretty much hold together for a few hundred thousand miles. About the time that a car gets lunar mileage, things like A/C compressors, brakes, suspension and exhaust components start failing and it's pretty hard to justify spending $500 for A/C work on a car that's only worth $1000.
In the 1950's it was the rare car that had 100000 miles on the clock, because waaaay back then, people built cars and motors (today it's done by robotics) and most people drove a heckuva lot less than we do today.
Now?
Even the humblest of cars are pretty much guaranteed to give you 100,000 miles before you have to even change things like brake pads (unless you drive like a moron) spark plugs, etc.....let alone do a motorectomy.
If you do have to swap out the motor?
A quick trip to eBay will show you that it's almost cheaper to buy a used motor than it is to buy a new A/C compressor.
Change your oil at any interval up to the factory recommended 10K (I use 4-5k) and use any oil that's cool with your OEM. If you're like most people, you'll fall in love with your next new car long before your old car goes off to car heaven.

Parents will drink tap water.....but for their BABYs??!!!
No way man!!!
It's got to be certified pure nursery water in a new BPA-free container.

Same thing.