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Synthetic oil advantages: longer drain intervals, better flow - gets to critical components faster, can promote longer engine life due to using smaller molecular particles vs conventional oil, best cost per mile depending on drain interval, lowers component friction over conventional oil.

Using full synthetic oil at its maximum drain interval offers the same protection as conventional oil does at its maximum drain interval. Using synthetic oil and draining it early is still more beneficial for the engine over conventional oil, although you lose some of the cost savings.
I agree except the following:

Based on oil analysis results, it is debatable whether using synthetic oil can extend your oil change interval. Conventional oil when changed at recommended OCI meet all oil criteria for engine protection. While synthetic oil if changed at extended OCI meet only most oil criteria. The conclusion is that although synthetic oil is far superior than conventional oil, it is only by following the recommended OCI that will give you the guaranteed results.

In terms of lubricating properties, synthetic oil only offers around 1% better lubrication than conventional oil at normal operating temperatures.

Again, under normal driving conditions of the general public, synthetic motor oil is a total waste of money. However, if you drive aggressively or in extreme weather, then you will need the extra protection offered by synthetics. But you still have to stick with the recommended OCI unless the oil is specifically formulated for extended use.
 

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I did various oil analysis for three years on my '99 Taurus (alloy block) and '00 Durango (iron block). As I had mentioned it's better to stick with conventional in vehicles that use iron blocks as more sediment contaminates the oil quicker. I managed to put on 12,812 miles on my '99 Taurus (145hp 2valve engine) in 7 months and sent in 2oz of oil for analysis. The results showed I was getting high in copper, and I could drive another 9K miles without issue. Most of those miles were highway.

My Durango on the other hand, who's engine is based around 1970's architecture couldn't drive more than 6500 miles on the same oil. I went back to conventional oil and changed it every 5K to be on the safe side. The original "LA" block my 5.9L is based on, was rated for 3K oil change intervals. If I can find any of the results in my filing cabinet I'll post them up. To stay unbiased I didn't use Amsoil's oil analysis company, I stayed within Canada and used Wear Check.

My G6 GT had similar results to my Taurus but with the autostick, I drive it harder so I only get about 15-16K out of an oil change. It works out well as I only put on about 10-13K miles a year thus I only need to change the oil once a year. $51 a year for full synthetic oil is decent, not to mention the time savings from changing the oil more often.

My only qualm with the G6 V6 is that it only holds just over 4 quarts of oil. This is my first four wheeled vehicle that doesn't hold at least 5 quarts. The V6 also has a vertical oil filter and is by far the easiest vehicle to change the oil on that I have owned.

I traded in my '99 Taurus last year for a 2012 Chrysler 200 Ltd V6. Taurus needed a slew of fixing that doubled it's current value. As the 200 is still under warranty I get the dealer to change the oil, but I supply it. As it's my new highway car it too will get the full synthetic treatment.

Just to add that I don't go by the on board oil monitor on any vehicle. It doesn't 'check' the engine oil, it merely calculates various parameters to determine when to change the oil. I don't trust the system as it can't be calibrated to account for full synthetic oil.

Here in Ontario, a quart of conventional runs upwards of $5.19 (average price of 3 - QS, Valvoline, Petro), and full synthetic is only $2 more a quart. Blended oil can be had for around $6. QS conventional 5W30 went on sale last week for $2.99/quart so I picked up a box (12 quarts) for my Durango.
 

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Fair enough.

We used to get oil analysis done on our fleet vehicles and wanted to utilize the benefits of synthetic oil. But time after time it wasn't recommended by the oil lab, our accountants, and the manufacturer to use synthetic oil in order to extend the OCI. There is no question synthetic oil will outperform and outlast conventional oil, but test results were inconsistent as to by how much. So far, only extended life synthetic oil were proven to be safe for extended use.

Generally speaking if synthetic oil cost less than 50% more than conventional oil, then it's well worth the money to use synthetic.

GM's Oil Life Monitor is based on an algorithm that mimics an optimum OCI based on oil analysis results. It is not fool-proof but it is reasonably accurate. Yes it's only based on type of oil the engine was originally designed to use (i.e. conventional oil). Unfortunately, there is no standard or formula to say how much longer synthetic oil can last. Given all the different brands out there, doing an oil analysis yourself is the best way to go.
 

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I use mobil 1 5w-30 fully synthetic high mileage oil, with a AC Delco oil filter. Always gets changed every 3000 miles.

Bought the car from my uncle with 127k miles (hes a csr guy, always changed it every 3000) and she now has 202k miles and still runs like a champ! Shes a good girl...
 

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Most engines are designed to run on conventional oil to give full protection under normal driving conditions for the life of the engine.
Synthetic oil will gives you added protection, but 99% of the time this extra protection is not needed and is therefore a waste of money.
That was true decades ago not so much now days.
Most FORD vehicles for example come with a Semi-Synth Motorcraft oil in them.
Many performance cars come with FULL synthetic oil from the factory.


A FULL Synthetic oil will keep your engine cleaner (not making carbon) and your engine will run cooler (less friction) AND you have more protection on a cold morning at start-up because of the better flow with synthetics.
IMOP those benefits are not a waste of money, but it's your money.

Almost ALL drivers drive in some conditions that make their engines qualify for "severe duty". If you want your engine to last always follow the severe duty recommendations for maint. intervals in your manual.
 

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That was true decades ago not so much now days.
Most FORD vehicles for example come with a Semi-Synth Motorcraft oil in them.
Many performance cars come with FULL synthetic oil from the factory.


A FULL Synthetic oil will keep your engine cleaner (not making carbon) and your engine will run cooler (less friction) AND you have more protection on a cold morning at start-up because of the better flow with synthetics.
IMOP those benefits are not a waste of money, but it's your money.

Almost ALL drivers drive in some conditions that make their engines qualify for "severe duty". If you want your engine to last always follow the severe duty recommendations for maint. intervals in your manual.
If the factory recommends semi-synthetic or full synthetic, always use them.

Yes full synthetic will keep your engine cleaner, cooler, better lubricated, etc...all true. But it's still a waste of money because regular oil already give you 100% full protection. The question is "Will the extra benefits of synthetic oils benefit you?". Synthetic oil is something you want, not something you need.

Yes definitely follow the severe duty recommendation. Doing so will make your engine last longer than using synthetic oil and not change your oil regularly. The surprisingly fact is that sticking to a proper oil change interval is
much more important than what type of oil you use.
 

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I have used nothing but Mobil1 EP since i've owned my first car (1997 Honda Civic HX) and any time i get a new vehicle that has a bit of miles on it and i don't know much about the oil change history, i will put some Pennzoil Synthetic with a bottle of seafoam to try and knock out any sludge and change it to my Mobil1 EP no real reason for using that particular one, though it does feel like it runs smoother with it..
 

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Just hit 103,000 miles and switched to high mileage Valvoline conventional from their standard oil. Doesn't lose or burn any oil at all.
 
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