Long change synthetic or short change regular?

[KW]

Couldn't you shed the fuel by going for a longish drive say 40 or 50 miles and burning/evaporating the fuel off?

I ran my last OCI for 10,400 miles and the fuel was <0.5%.

 

[Ed]

Thats a question thats been asked frequently ever since synthetics made their appearance on the automotive scene.
Justification for using synthetics is valid on either end of the the temperature extremes. At all "normal" environments the only real advantage is one of "insurance". What if your thermostat sticks shut or you lose a fan(waterpump) belt?
With synthetic in your crankcase (even if it has over 6000 miles on it) The length of time to severe engine damage will be materially increased.
If your a dude you probably will shut the vehicle down immediately anyway. If your a chick you probably wouldn't even slow down but turn the airconditioner on full becaue of all the heat coming through floorboard. My aplogies to the politically correct and automotive savvy females.
Ed

 

[mikemc]

A good point is made that synthetics are better performers at temperature extremes. For those of us who watch the gages, take care of the cooling system and don't see arctic cold, they are probably wasted money.

 

[SWS]

Posted by Curtis Newton:
I always thought you wanted the oil to get dark because that meant it was doing its job. In other words, the oil is holding the by-products in suspension until it is drained out.
------

Yes, that is what I think too, but I don't think that is always the whole story! My hot-headed Camry engine is tight and clean, so there are not many byproducts of combustion in the oil. Also, with frequent oil changes since it was new, it never had a chance to sludge-up. Given that the oil actually looked cleaner in the winter than in the summer (opposite of my experience with other my cars), I concluded that in my case that the rapid darkening of the oil in the summer was due to heat stress (oxidation?) of the oil. A UOA would have to be performed to confirm this hypothesis - I just look at the oil and let it "speak to me" (just kidding!). Anyway, my recent experience with M1 is that it has stayed the nice "new" color all summer, which adds to my thought that there are few "contaminates to hold in suspension".

 

[SWS]

Another reason to use Synth instead of Conventional oil:

Synth is claimed to have less volatility than Conventional oil. Mobil says that M1's volatility is approx 50% of Conventional oil. The spec on volatility is less than 15% of the weight. To me, that is a lot of oil lost! Especially for frequent oil-changers like me, the fresh Conventional oil "boiled off" frequently, adding oil to the intake system and probably coating the valves with crud!

 

[kbohip]

Hmmm, well after hearing all this great information I'm still confused as what to do. I really don't want to shell out the extra $30 for an oil anlysis at 3k miles if I don't have to. What do you guys think of me waiting till 6k miles and then having the analysis done?

 

[XS650]

quote:

---

Originally posted by kbohip:
What do you guys think of me waiting till 6k miles and then having the analysis done?

---

Go for it, 6k miles on asynthetic is pretty conservative. No need to do frequent oil analysis either. Do one at 6,000 miles and if you don't see any problems, no need to do one again soon.

I doubt that 1% of privately owned cars get frequent oil analysis and modern cars aren't falling by the roadside at a high rate. Oil analysis on privately owned cars with decent maint. is educational and entertaining, but hardly necessary.

 

[Bill Morris]

That would be wise at 6K with synthetic oil. From there you have an idea what is going on with your oil and engine for further extended OCI.

A good quality synthetic oil can go 6K. Mobil 1 which is easier to acquire comes to mind. Amsoil is another synthetic oil which can be purchase through a dealer.

 

[XS650]

quote:

---

Originally posted by SWS:
The spec on volatility is less than 15% of the weight. To me, that is a lot of oil lost! Especially for frequent oil-changers like me, the fresh Conventional oil "boiled off" frequently, adding oil to the intake system and probably coating the valves with crud!

---

Oil loss from volitility in a real world engine is much much less than that. My wifes a car and mine both lose less than 2% of their oil in 6,000 miles due to all causes. My car, less than that 2% on M1 and dino Delvac Super1300 also is showing no loss after over 2,000 miles in my car.

 

[Geoff]

KW - agree the fuel boils off on long runs, usually. Problem is, when do you know the oil is fuel diluted (other than constant UOAs)? New car in good tune, no worries. Older car running in the winter on oxigenated fuel, dunno.

I bought a used SUV with 88K. It had decent oil change records, around every 7500 k per book. Turns out the engine was heavily coked and varnished. The crankshaft bearings all worn through to copper when I dropped the pan at around 100K miles.

This is a project vehicle, but I am left thinking, gee if the previous owner had spend the extra $40 annually on another oil change I might have avoided a Saturday on my back under a smelly engine.

 

[Audi Junkie]

quote:

---

---

 

[Audi Junkie]

quote:

---

Mobil says that M1's volatility is approx 50% of Conventional oil.

---

Mobil says this, Mobil says that. They are comparing their top oil to the lowest grade oil available in the conditions most favourable to their product. How many engines see these temps regularly anyway?

How about comparing to the newest top-notch conventionally-priced (<$2) oils or others that compete directly at that price-point?

 

[Dr. T]

Yeah no doubt. The oil turning dark and then black means it's getting spent....just like the oil in your favorite frying pan. The heat kills it. Synth's hold up better. A3 synth's hold up even better yet...

 

[Tim]

quote:

---

Originally posted by RedWolf4000:
Im not a chemist, but if oil appeared to show less wear after its first 3000 miles, wouldnt that mean its becomming saturated?

(I may be wrong) but doesnt oil become saturated when it suspends dirt and wear particles? If this is true, wouldnt it make sense to see less wear in the engine after 3k, even though there actually is the same or more wear going on, but the oil just doesnt do its job of picking it up to show in the report??

Please correct me lol.

---

RedWolf4000 this rant is not directed at you, I just picked this spot to reply:


Well, I am a chemist and I say this is total nonsense...the idea that wear rates/mile are higher when the oil is fresh.

Anyone who has had a 200 level analytical chemistry lab will tell you that the wear metal rate only appears higher per mile early on because of either contamination from left over oil or stuff in the virgin oil.

Let's apply a little common sense to this. How on earth will clean oil allow for greater wear than dirty/depleted oil?

Don't forget to factor make up oil and filter changes...


Tim

 

[Robbie Alexander]

What Oil?
M1 fairly sure. Me I'd go 6-7 Drain and sample
And refill
I assume Terry is doing the test.

The point is to spot a trend.
But you also have to know what it looks like at certain levels too.

If the oil on extended drains can go for 14-18+K miles, that doesn't mean its okay to just skip the rest of the sample times. You should plan on sample at the same areas or miles.
I.E. 4k/8k/12k(drain): REPEAT for the known if your service is about 12K.
I.E. Service is 28K
you may go: 5K/10K-then filter replace/15K/20K-then replace filter/25K/drain
or whatever
I.E. Service is at 8-10K
4k/8K-drain
5K/10K-drain

You have to always do testing on extended drains to be safe.

Cheers

quote:

---

Originally posted by kbohip:
Hmmm, well after hearing all this great information I'm still confused as what to do. I really don't want to shell out the extra $30 for an oil anlysis at 3k miles if I don't have to. What do you guys think of me waiting till 6k miles and then having the analysis done?

---