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My 2005 Prius is 7 months old and has only 2,500 miles on it. A service employee at a local Toyota Dealership told me that I could drive another 1,500 miles before the car would actually require an oil change, even though the Service Manual says 5,000 miles OR 6 MONTHS MAXIMUM between Oil Changes. Was I given valid advice? Any opinions?
 

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I never understood the concept of changing oil by the months rather than the miles. I mean that oil is several million years old anyway. I think you are overdue for a road trip! :)
 

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Time does not wear out oil, but each night as temps drop, moisture from warmer air condenses in your crankcase, adding water and creating sludge. This is why they recommend you change the oil by the calender if you don't drive much.
 

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KTPhil said:
Time does not wear out oil, but each night as temps drop, moisture from warmer air condenses in your crankcase, adding water and creating sludge. This is why they recommend you change the oil by the calender if you don't drive much.
That depends on several factors:

o Was the car driven long enough for the engine to reach operating temperature and evaporate any residual moisture?
o Do you garage the car (attached garages rarely cool to the dewpoint)?
o Are you running synthetic oil (those don't sludge)?

to name a few.

Mike
 

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Wow.

I'm learning more and more neat stuff every day.

I have a detached garage, uninsulated, but it's San Diego...how cold can it get really?

When I do take the car it it does get a change to warm up so I'm sure any condensation does get cooked away.

I don't drive that much like about 5,000 a year. Really. So I'm looking at the time/distance thing.

I bought my car in April so my first oil change is scheduled for October. However I am bringing my Mobil 1 synthetic oil (three only) with me for them to use to change oil. I'll add another half when I get home. I don't trust them. Right now my oil is overfull and I have to wait until October's oil change for it to be done correctly. If they overfill it again I have no way to get it out.

So if I'm reading this correctly, after I switch to synthetic I can get my oil changed every 5,000 miles rather than every 6 months. Which will be nice since the synthetic is more expensive.

Thanks.
 

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Well, technically, that would be true. However warranty requires 5K/6mo, so if ICE ends up developing a problem, not changing oil at specified intervals could void that. Once the warranty (factory or extended) is up, then you can change oil at intervals you feel apropriate.
 

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It won't get all that cold, but the temp differential that matters isn't ambient air, but the temp in the crankcase. That is still wide enough to get condensation. Say from 300F to 70F, you may hit the dew point by morning given the humid coastal air.
 

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They had a guy call into car talk recently.

He has a big truck that he drives very infrequently (1,00 miles/yr ish). the guy didn't see the use of changing the by time, so he went 3 years to get his 3,000 miles in. The first thing that came out was a gallon of water, then clean oil.

My understanding is that it's not the air temp changes, but more the fact that he didn't drive it far enough each time for enough heat to build up to remove the water from the crankcase. The moisture comes from combustion more than ambient air.

Of course, I'm just another idiot - what do I know?
 

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I bought an attached patio home (one end of a 3-house set) and notice that the cars under carports like mine have little or no condensation on them in the morning, while windows are fogged over on the cars left out in the open.

I'll buy some value in covering the car (even lightly like a carport) overnight, but internal condensation affecting the oil still seems like a stretch...
 

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It's not condensation from the ambient, it's blow-by of water vapor produced in combustion. Burning a gallon of gasoline makes roughly one gallon or 8 pounds (mass) of water (along with about 20 pounds of carbon dioxide). Some of that blows past the rings and into the oil. Regardless of the source, if an engine spends an insufficient fraction of its time running hot then it won't evaporate all the water out of the oil.
 

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I wouldn't gamble the long-term health of my engine by skimping on $20 oil changes every six months. Do it your self for less than $5.
 

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Just checked my service scheduel The first (and repeat interval) here in Europe is 12 months or 15,000Km whichever comes first.

I will be getting my firstg oil change/service next month at circa 12,000 as end of the month we are going on a long 4 week trip with the car to Greece.

How come your interval is so short (other than to allow MRT to make more money from you)?
 

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Victor said:
Just checked my service scheduel The first (and repeat interval) here in Europe is 12 months or 15,000Km whichever comes first.

I will be getting my firstg oil change/service next month at circa 12,000 as end of the month we are going on a long 4 week trip with the car to Greece.

How come your interval is so short (other than to allow MRT to make more money from you)?
In Finland, the first oil change is at 3.000 km, then at 15.000 (or 1 year). The 3.000 km oil change here is optional byt Toyota recommends it.
 

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dontcheff said:
In Finland, the first oil change is at 3.000 km, then at 15.000 (or 1 year). The 3.000 km oil change here is optional byt Toyota recommends it.
Interesting. Thats not in my handbook/schedule. I even asked the dealer about it and he said "not required"
 

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Victor said:
Just checked my service scheduel The first (and repeat interval) here in Europe is 12 months or 15,000Km whichever comes first.

I will be getting my firstg oil change/service next month at circa 12,000 as end of the month we are going on a long 4 week trip with the car to Greece.

How come your interval is so short (other than to allow MRT to make more money from you)?
That's what I have been repeatedly asking. Yes, the oil may be better in Europe, I won't argue that. But we are using the same engine that creates the same contamination. Few have come close to explaining the discrepency. The closest was that the oil and filter can trap or neutralize the contamination better with synthetic, or european oil.
 

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Oil Change Frequency - US versus Europe

There have been several other Oil Change threads on this site.
I recall reading that the longer Oil Change Interval in some European countries has more to do with their traditions and perhaps regulations. People there may not want to waste resources and add waste by changing oil too often.

By the way, another good reason to use synthetic oil, according to a August 2005 Consumer Reports article, is that several modern 4 and 6 cylinder engine designs including those in popular Toyota, Saab, Chrysler and Volkswagen vehicles have had low incidences (0.2% for Toyota's) of catastrophic engine failure due to oil sludge blockage. The synthetic oils may be able to better withstand oil degradation during the high operating temperatures that may be linked to sludge formation and subsequent oil passage blockage. Short trip cycling coupled with high temperature operation seem to be the key risk factors.

'Sludge' Defined: An emulsion of water and combustion byproducts forms during low temperature operation. High Temperatures may then oxidize and/or polymerize this into a hard gelatinous residue (Sludge) that may plug vital oil passages in the engine.

I have read that this sludge problem is virtually impossible to create in the laboratory but that it obviously happens at a significant frequency on the roads.

Finally, when I lived in Minnesota for one winter, I noticed that my Honda Civic's oil formed a gray emulsion during warmup during the colder days. Some days were too cold for the engine temperature to rise sufficiently to completely drive off the water; particularly during short (<30 minute) trips.

The unique Prius 'frequent engine on/off cycling' behavior may add to sludge risk.

Your thoughts?
 

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I would expect less sludge in the Prius; the use of the thermos to retain warm coolant for later startup should result in less cold running, and therefore less sludge.
 

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Re: Oil Change Frequency - US versus Europe

rghadimi said:
Some days were too cold for the engine temperature to rise sufficiently to completely drive off the water; particularly during short (<30 minute) trips.
In live in Minnesota and get heat from the engine in just a few minutes, even in the coldest weeks of the winter.

This misconception is really becoming annoying.
 

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John, can you show data on temperature rise in the oil system and temp rise in the coolant system? I would not assume that they are the same. I would not even assume that the oil was always hotter than the coolant.
 

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Althought the ICE is turned off or run at very low power sometimes, the ICE is running most of the time, usually not long enough to be considered cold after the first 5 minutes. The O2 sensor and calalytic would cool much sooner than the oil would, thus would put the ICE into the less efficient open loop mode. You don't usually see that happen after the 1st 5 minutes of a trip.
 
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