Can you "feel" a difference after a regular oil change?

Yes, longer change intervals is what synthetic is good for. When Mobil 1 first came out, Mobil was promoting 25K miles between oil changes, but they quickly backed down from that recommendation because they didn't want to be liable for warranty issues resulting from owners violating the required oil change interval in the manual.

Now the longer change intervals are finally making it to the U.S.. The Mini Cooper is at 15K miles now with synthetic. Going beyond 15-20K is dicey, not because the oil no longer lubricates, but because of the acidity caused by the by-products of combustion. If you could add some more additives that neutralize the acid, you could go even longer.

One reason why synthetics last longer is they already have more additives. The additives often cost more than the base stock oil.

Jeff

actually, it's stability of the base oil, not so much the additives. because the base is highly refined, it doesn't have nasties in it like aromatics, branched chains, sulfur, etc. thus the base, 1-decene for example, is highly stable, and so doesn't break down. indeed, 25k was mobil's original stance on synthetics because it was a real number, and they were prepared to unconditionally guarantee it too. but it's not good for sales and dealer service profits, so they backed down. you can try it yourself though - just send oil in for analysis and see how it's doing.

Hi, How about starting with definition of synthetic?

actually, "synthetic" is hokus pokus. been to the auto parts store lately? looked at brake fluid? noticed how there's a premium on "synthetic"? well, /all/ brake fluid is "synthetic"!

for motor oil, provided the base stock has the required formula, it doesn't matter whether it was refined or synthesized.

one more thing - despite the fact that "synthetic" motor oils can indeed be superior stuff, their price premium is a rip compared to production price. in indonesia where there's a large g.t.l. [gas to liquid] facility that manufactures a lot of the world's synthetic oil base stocks, the stuff they don't sell for lubes is sold as diesel oil. yes, it's that cheap.

Hi, Where do you live? Have any experience driving in sub-arctic zone where they never shut off engines once it is started in winter time? Even where I live, it is PRETTY cold in the winter. Including wind chill, temp. can reach down to -45F or so. Synthetic oil DOES make big difference.

Hi, Dull people can't even imagine, LOL!

Actually one benefit of the synthetics is that the superior base stock needs less additives to maintain viscosity, so you get more base stock and less viscosity modifiers.

Synthetics become acidic, and eventually become saturated with suspended soot particles, just like regular oil.

An oil analysis is a good investment to determine the optimum oil change interval, but since you really shouldn't be exceeding the manufacturer's requirements during the warranty period, and the manufacturers are very conservative, there's no benefit to using a synthetic if you're doing

Yes, it's true that synthetics have a benefit in extremely cold climates.

But go by the actual temperature, your car engine doesn't care about the wind chill, which is solely for body heat.

If I do it myself - No change... If I have it done by someone - most definitely!!!! My wallet always feels much lighter!!!!!!!!!!!!

DaveD

What a complete lot of nonsense. If the lubricity of the oil changes in any perceptable degree, the engine bearings will fail. Particle entrainment in the oil does not increase viscosity. Incidentally where are these particles coming from? Surely you are not suggesting these are metallic particles from engine wear. Where do you people get their technical education from?

Just like after a thorough car wash.

Or a new set of JDM "speed" decals... ;-)

the oil does indeed make a difference - i'm talking about the word. "s-y-n-t-h-e-t-i-c" is primarily a retail marketing device. "group IV" is what the industry uses.

/all/ motor oils become acidic. that's because of combustion product.

er, the whole point of using analysis is so that you /know/ the condition of the oil. wtf would you disregard analysis in favor of guesswork?

you've worked with cars for /how/ long???

how odd - when you /measure/ viscosity over time, if the base doesn't degrade, viscosity goes up! strange how misleading measurements can be!

er, it's called "combustion product". ever heard of that in a "combustion engine"?

there's all kinds of crap in there. anything too small for the filter remains in the oil. duh.

clearly a much better place than you.

If you're changing every 3-5,000 miles, then most likely you won't/ can't detect a difference. However, if the oil level was down a quart or two, and was excessively dirty, then I can at least entertain the possibility that it would make a difference with fresh oil hitting all the lubricated surfaces inside the motor.

After changing the oil on a friend's car after 11K miles between changes, I recall that it seemed to idle smoother and quieter afterward.

.> Is it possible to feel a difference (smoothness, better acceleration,

Well, not being a mechanic, I would've guessed the engine is controlled by a tightly timed ignition system rather than how lubricated the engine is.

Al

Mine runs better just after it's washed and even better if I get it waxed too.