ES - Change in Maintenance Schedule from 7,500 to 5,000 Miles

I've used 10w-40 for many many miles back when this weight was most common AND when supposedly these "terrible things" occurred. Never even had a single lubrication problem. Even used this weight in air cooled motorcycles having a common oil sump with the gearbox and wet clutch. Haven't used 10w-40 natural oil since 1990 when I bought a new Geo Prizm and started running Mobil1 10w-30.

Philip:

Even in sub-zero conditions, the oil will get hot enough to boil out any extra humidity, of course assuming that the engine runs long enough to heat the oil to normal operating temp.

I have never found an owners manual that says to change the oil more frequently in rainy conditions. Short trip driving (in any temp) or dirty air or heavy towing call for increased oil changes, but not rain.

SF

Not to mention leather, rubber or PVC. ;-)

John

this is what I would think as well. The only way you are going to get anything to condense inside an engine is if you don't let it warm up and then shut it off. Here in the south, we frequently have 100% humidity at night and early in the morning. The relative humidity is not necessarily higher during rain unless the air temp gets as low as the dew point. For this to be a concern you would have to use the vehicle to just drive to the end of the driveway and back every day. If it warms up at all inside the engine then it would be almost impossible to get condensation inside because the relative humidity would be almost nonexistant at engine temps.

A more probably situation would be a car that is rarely driven and it gets cold at night. Then when the ouside air warms up outside the cold engine could condense vapor inside the engine.

I guess there are many possible ways to get condensation inside an engine but all of them would be negated by driving the vehicle at operating tempeven for a few minutes to boil off any accumulated moisture in the air spaces and therefore in the oil.

So long as you don't shut off the engine and you continuously drive at moderate speeds, then I agree. However, I've seen sludged engines in local delivery trucks (gasoline) that were operated in sub freezing temperatures. Thankfully I didn't live in that particular place (Billings, MT)(visiting friends there). You mention the Owner's Manual list of "severe" conditions. I put this question to you: How often do you see Lexus' driven regularly on dusty dirt roads, or pulling a trailer, or using a roof-top luggage carrier? Virtually none! Makes you wonder what is going on with these qualifiers, doesn't it. So you might think that you're qualified for the 7,500 schedule, maybe a bit longer. Seems V6 Lexus/Camry powerplants are just a bit unforgiving under REAL world conditions ... which include short trips with cool downs between stops, humid driving environments, very cold environments with longer than typical idling time, and prolonged slow speed driving. Each of these dictate shorter oil service intervals because each is conducive to combustion byproducts accumulating in the oil. Take a look in your Owners Manual. There should be a short chapter about "oil consumption." There is in my Corolla book. All this is nothing new to the internal combustion engine so I'm curious why you're fighting the obvious.

Takes quite a bit longer than a few minutes. I worked for a delivery van fleet back in the mid '70's. The contract we had required periodic oil analysis on all vehicles once off warranty. Without going into a bunch of detail, the upshot regarding water condensation and fuel accumulation in the oil came the order that all trucks were to keep the engine running for the first 45 minutes, afterwhich they should be shut down at delivery stops. These were gasoline Chevy and Ford engines with carburetors. After about three months, the test analysis trimmed that back and settled on 30 minutes. This was in the Los Angeles area which can get humid but not like that "southern humidity" of Florida.

Phil, you are talking out both sides of your mouth on this one. I never mentioned combustion byproducts in my replies. They could accumulate in any situation where the engine runs alot without really heating up extensively. Your delivery truck scenario is exactly like one of the situations I described that WOULD allow condensation to accumulate in the oil, cold temps, short operating intervals, and never a good hot engine temp. Aside from that I doubt you could get condensation to form inside an engine and not boil off from heat. Other than that we found common ground if you will just recognize it.

Speaking of obvious, you think it should be obvious to everyone that your corrolla is superior to any of our Lexus models because it has a throttle cable.

Philip:

My post only was in reference to your comments on the need for more frequent oil changes in high humidity. I guess we can agree to disagree on that point!!

I agree with you that a 5k oil change is better than a 7500 mile oil change. I change my oil at 5k miles on all my cars. Oil is cheap, so why push the miles past that is what I think. Plus, the wife only drives 6 miles to work, so I doubt the oil gets all that hot, but without an oil temp gauge, who knows. For what it is worth, my neighbor had an oil temp gauge that he added to his 57 Chevy 283 cubic inch V8. It took just about 10 miles of stop and go traffic for the oil to reach normal operating temp.

I also have had good experience with 10-40 weight oil, before the newer 5-30 stuff came out. I had an 86 VW Jetta that went over 160k miles before I sold it. Only burned 1 quart every 3500 miles. No lube failures whatsoever.

SF

"Combustion byproducts" is an all encompassing label for all substances that contaminate your oil which in turn necessitate periodic oil replacement.

If you will open your Owners Manual, I should imagine the same section titled "Oil Consumption" exists in your Lexus book as exists in my Corolla book. For the most part ... apparently ... we are on the same page if you'll permit me to expand on one or two of your points. :-)

You have my permission and attention.

:^) SF, thank you for making my point. Take your friend's 57 Chevy experience and add continuous cold water spray to the oil pan exterior. What does that do to oil temperature? ;-)

Well okay, this horse is lookin' pretty beat.