TJ, I believe you've reached the wrong conclusion. This is how it was explained to me long ago.

Water is a byproduct of combustion. Ever see water spitting out the exhaust pipe of a car that's just been started? Some small amount of this water is mixed in with the oil, crank churns oil and mixes in water. If the oil is brought to normal operating temperature the water is for the most part eliminated. If the oil isn't brought to operating temp, water stays in. Enough of this and you create a "mayonnaise-like goo" which is what water and oil combine to make.

This is (one) reason there is a mileage recommendation and ALSO a time recommendation for oil changes. I think you most certainly qualify for the severe schedule and I'd follow it religiously.

 

[QUOTE]Originally posted by ruexp67
I have heard (and this IS annecdotal, but it was from an airplane mechanic.)

 

Ok, OK!! I'll take the freakin' long way to work! And follow the severe maintenance schedule!! Sheesh

TJ

 

Road Rage,

Is it that MORE water is produced when the engine is cold as opposed to when it is at operating temp? So more cold starts, more cold running, produces more water than the same number of hours run continuously and at operating temp, correct?

And the water that is produced stays in the oil no matter that the car is brought to normal operating temp?

Just trying to understand what's really going on.

Thanks,
Gary

 

Also, is this true for all engines? My 03 Rav4 manual doesn't have anything about severe driving maintenance....

TJ

 

Yes, a bit more water in the blowby, because the engine combustion efficiency is not optimal during warmup, it si richer as well, and the ring alignment is not optimal. Just havubg the car sit picks up water vapor - but it will not form the gooey white mess someone mentioned unless there is a cylinder headgasket, head crack, or block crack - there is not that much vaporization int he oil sump.

No, the small amount of water in thge oil from normal driving is completely eliminated as the car oil temp gets over 200 degF, but it takes 10 minutes or so - frequent short hauls do not allow it to happen, and the process of acidification I described can occur. Read carefully what I wrote - there are additves (detergents, represented by the higher TBN numbers of better oils, that have a great capability to deal with acids/ocidation. Red Line is high, Amsoil close to 11 or 12, while Mobil1 is about 5 (no better than regular mineral oils like Pennzoil or Valvoline). That is the main reason they do not recommend extended drain intervals. I think a high quality synoil is a good choice for someone who does not drive a lot, and does not want the hassle of frequent oil changes.

 

Of course it is true - it is true of all internal combustion engines. They do not mention it because they go out of their way to dumb down maintenance frequency and maintenance costs for the average nitwit who could care less whether their car gets the best treatment. Look at all the Camry owners who went 7500 miles with rot gut el cheapo oils, and wondered why the lousy oil galley design of the Camry resulted in excessive clogging and mucking up, esp. in the V6's. It was owner ignorance and Toyota promotion.

You also have to remember that cars like the Camry dumb down maintenance because they appeal to fleet buyers, who fcator in things like maintenance costs to figure the TCO (total cost of ownership). A few more miles or even lowering the amount of oil in the pan (old trick) can mean millions in sales.

Use your head!

 

the distance from my job/school to my home is only 5 miles. when i go to work/school, i let the car warm up to 2 bars on the coolant temp gauge and by the time i get there everything is at normal operating temperature. when i come home, i take a very fun backroad which extends my trip to 15-20 miles. this long route allows my car to fully warm up to normal operating tempeartures and allows me to breakin the motor with engine compression braking and various rpm changes.

 

I'd like to clarify some points on the corrosive nature of the exhaust:

The primary products of combustion in an engine are carbon dioxide and water vapor. When the exhaust system is cold (as when you start your engine), the metal surfaces are colder than the condensation temperature of the water vapor, and therefore the water condenses on the inside of the exhaust system. The last part of the exhaust system to reach dew point temperature is obviously the end of the exhaust, or the mufflers. Modern mufflers are designed to either have weep holes to drain condensate, or are sloped to allow the condensate to drip out the tailpipe. But not all of the condensate can be removed from the system this way.
That's why allowing your engine to warm up is important - if you don't, then the inside of your muffler is like a humidity chamber. Since you also have residual sulfur from the fuel as well as carbon (not tied up in gas), you form carbonic and sulfuric acid. As the condensate evaporates, these acids get relatively concentrated, causing them to be quite corrosive.

Your "cold end" (after the converter) exhaust system is made from type 409 stainless steel. This is much better than the OEM exhaust systems made decades ago (or the aftermarket exhaust systems) which are made of aluminized carbon steel. But type 409 isn't a very good stainless steel. Over time, temperature cycling and humidity take its toll. I've been invlolved in exhaust surveys that have shown that mileage has little effect on the longevity of an exhaust system, except if the systems have seen very high temps or if they have been driven short distances frequently. IMO, 15 minutes should be long enough to dry out your mufflers.

As far as the effects on the engine, I'll defer to Road Rage's comments.

 

Thanks for the build...I expected that people would infer from my "internal" response that the exhaust had the same issue - corrosoives fromt he action of water and phosporics/sulfurics. The phosphorics are primarily from oil additives, and are much less plentiful than the sulfurics.