15,000 mile oil change interval

If you start using Mobil 1 0W-20 - or any synthetic - in a Prius with under 10,000 miles on it, you will have good results. If you run that motor on a coventional oil for a long time, say in excess of 50,000 miles, do NOT try using a light synthetic like a 0W-20

FWIW my 2004 Prius I ran synthetic starting at around 10,000 miles. Running Mobil 1 0W-20 up to 16,000 km oil change intervals, the level went down maybe halfway between the full dot and the add dot

The made in Germany Castrol Syntec 0W-30 is a good oil, it's considered a "thick" 30 at operating temps, and may control oil consumption.

If I were you, given the age and miles on that motor, I'd go back to conventional 5W-30. It's possible the use of Mobil 1 cleaned up deposits on seals, rings, etc, and now your motor will always consume a bit of oil

I would like to see a used oil sample done on that oil. You're just guessing if you go by smell, feel, color, etc

 

Did your oil consumption settle down, or is it still using unusual amounts of oil??

 

Hi Jay,

Oil consumption is back to normal now, using 5W-30. Looks like 1/4 quart was used in 6,500 miles.

I am going to change the engine oil/filter tomorrow because I have to take the Prius to the bodyshop on Monday, it will be in the "hospital" for at least 10 days, and I won't have time to change the oil later in the month prior to our move to AZ.

CC&Rs at my new home prohibit "car repair" so I will have to be low-key in the future, can't get an air compressor with impact tools or anything obvious like that... Too bad, because the garage has a dedicated 240VAC outlet that has no current purpose.

 

Fuel dilution of the engine oil is a known phenomenon with Prius engines. My UOA results were starting to get a little high for my taste at 8k miles so I decided on 7500mi changes on M1 as a nice round number. (Even 9k miles might have been fine but I like a little conservatism.)

That said, I think your 15 to 20k "experiment" without sampling is a little silly. Especially considering how ridiculously easy it is to do an oil change on a Prius compared to some other vehicles I've had. If you don't like your car, then fine. If you hate changing oil, pay someone else to do it.

1 quart in 5k isn't so bad. When I met my wife she was driving a car that needed a quart at every other fillup.

 

I used Mobil 1 5W 20 on all my cars for the last 20 years. I've changed the oil and filter every 15K miles (once a year) and never had a problem. The cars all got to over 100K miles before I sold them, and they never used any oil. When Mobil first introduced Mobil 1, they claimed 25K miles between oil changes. Synthetic oils don't break down like hydrocarbon oils.

 

False. Synthetic oils are hydrocarbons just like any other. The major difference is simply that the molecular chain lengths are more consistent than what you get from the typical refining process. They take longer to break down, but they still shear just like any other.

That said, breakdown of the oil due to heat and shearing is only part of what makes an oil useless. Oils also contain detergents to remove contaminants from the engine and hold them in suspension. These detergents lose effectiveness over time, and when that happens the engine will start to collect deposits. The total base number (TBN) is a measure of active detergent, and based on my own results the oil would be done in this respect by ~10k.

Also, the crud and wear particles that build up in the oil have to go somewhere. Yes, the larger particles get caught in the filter. But filters aren't 100% effective. And as others have already pointed out, filters can get clogged and quit operating. When that happens, oil bypasses the filter element. You would have no way of knowing that this happened without sampling.

Don't get me wrong, I'm all for using less oil and motor oil is included. But you also have to remember how much energy it takes to build a new car. It's tremendous! Modern cars, and particularly Toyotas, should be able to last 300k miles or more if they are well maintained. Even if the engine lasts 150k miles before the cams get torn up or it throws a rod due to inadequate maintenance, that's still half of what we absolutely know these engines can do.

 

I switched to Castrol Syntec 5W30 at 15,000 miles. My plan is to change the filter only every 5,000 miles and then top off the oil level. I will do this twice so I will have 15,000 miles on the oil and use 3 filters.

 

I agree. A $20 oil sample vs a +$4,000 engine.

No contest

 

I think that works if you do so from new, or under 10,000 original miles. If you wait until the engine has +50,000 miles, the higher detergency of the synthetic oil, the natural "laxative" action of the esters (Auto RX is in fact a highly concentrated ester additive), will cause problems with deposits

Run on conventional oils, by the time a motor has over 10,000-20,000 miles on it, you can expect deposits on the seal rotating surfaces, ring land area of the piston, crown land area underneath the piston dome, etc. Those deposits on the seal rotating surfaces can erode the seals

Switch over to a synthetic oil with high detergents and esters, expect that trash to be put into suspension, and leaks to start. I would never even *think* of switching a high mileage motor over to synthetic oils

I've had similar problems switching an axle in a early 1990's Chevy Caprice (Ex Utah Highway Patrol car picked up at auction) to synthetic gear oil. Within a couple of months the pinion seal and both rear axle seals sprung leaks. Maybe coincidence, probably not

 

I would strongly advise you sample the oil if doing that.

Most full-flow oil filters only catch +30 micron trash. You could change the filter as often as possible, it wouldn't do anything about the <30 micron trash that is proven to cause most engine wear

If you add on a bypass oil filter system, with <10 micron filtering, then your plan would work fine

 

From Mobil's web site:
What is the difference between Mobil 1® Extended Performance and Mobil 1? Mobil 1 Extended Performance formulas are designed specifically for today's longer service intervals and are guaranteed to protect for up to 15,000 miles or one year.

Mobil 1 Extended Performance has a unique formulation with a boosted level of protection and performance. Mobil 1 Extended Performance, with the Advanced SuperSyn System, contains 50 percent more SuperSyn than Mobil 1.
If I go longer between oil change intervals, do I need to change my oil filter more frequently? Or do I need a special filter? Continue to change your oil filter when you change your engine oil. Special filters, or more frequent oil filter changes are not required.
I can't find the reference now, but I remember reading a study done on NYC taxi cabs. They were run on Mobil 1 with 10K miles between oil changes for 100K miles. Then the engines were torn down. Wear was minimal, with another 100K+ miles projected life. Up here in NY it is rare to find a car with more then 150K miles. The roads, and the salt kill them. Everything else in the car starts wearing out, and the maintenance and inconvenience of fixing them all the time makes it impractical. Maybe a shorter change interval will give the engine another 100K miles, but from a practical point of view, if the engine is running, and the car falls apart around it, it is pointless to keep it going.

 

Lots of superstition in this thread... data, not so much

Reminds me of the classic discussion over "best method to break in a new engine". Everyone has their own opinion, no one has ever done a controlled experiment

 

There are UOA data on Priuschat but they have not been linked to this discussion. I will hazard to summarize that we have not seen growth in wear metals in Prius with III or IV synthetics in the 10,000 to 12,000 mile range. TBN gets low and this of course is one strong indicator of oil-change time. In this regard there is nothing better than knowing your own engine/oil combo, in other words, get the UOA.

I have not seen that fuel dilution increases over time in that data. Has anyone else?

 

If someone would provide the funds, I will go buy 10 of 2010 Prius and do the controlled experiment for you.

 

I can't tell you what to do. At the end of the day, we do what we feel is right for ourselves. For me, the 15000 mile Mobil 1 change works, and I have been using it that way on all my cars since Mobil came out with it. If you are not comfortable with the risk, follow the manufacturers recommendations, at least that is safe. I've only had an engine sieze once, and that was because it lost all the oil and my wife ingnored the warning light and kept on driving. I generaly keep my cars until they get too expensive to fix, 100,000+ miles and sell them. I never had one that burned oil (several leaked oil). Being near NYC, all the cars end up with lots of dents, so they are not worth too much.

 

I'm not too impressed with Mobil's Extended line of synthetic oils. In the teeny fine print, the caveat "while under warranty, follow manufacturer recommended blah blah blah"

Mobil does sell an oil that specifically meets the EU ACEA definition for extended oil changes up to 18,000 miles: Mobil 1 European Car Formula 0W-40

Since 10,000 miles or 12 months is the normal interval in the EU for Toyota cars, running ACEA spec oils, there shouldn't be any concern with high quality oils here. If the motor already has a lot of use with conventional oils, I would NOT switch to a synthetic.

Using a lighter oil, like a xW-20, is ok with a new motor. Not with a used motor

 

I'm getting the best mileage I've gotten so far using the Mobil1 5W-30 Extended Range (store didn't have the standard stuff.) Can't say that it is the oil because I went from 3.5 to 3.0 quarts for the fill too.

 

Related to this was a recent experience with a national oil change chain.

The shop manager refused to warrantee the oil change, unless I used a synthetic oil.

Claimed that all Toyotas would suffer engine damage from convential oil.

I complained to the "home office" and they supported their guy.

This happen to anybody else?

 

That may have been related to the oil sludge issue Toyota had with some of their engines. One consequence of that class action lawsuit was that Toyota universally lowered - in North America - their oil change interval down to 6 months or 5,000 miles

That said, there are Toyota's out there with +200,000 miles, run on cheap oil

 

Iffy Lube? One of the Clones? They have a great reputation:

What's Wrong At Jiffy Lube? Learn remedies. Add your experience.

How convenient for them, I bet they charge more for syn oil too.

I would have asked for something in writing to this effect.

Sure, they are just as clueless as their guy.

No, because I would never take my car to one of those places. They don't care about your car, they only care about your money. If I couldn't do the work myself, I would try to find a competent independent shop to do the work.