15,000 mile oil change interval

IMHO waiting 15,000 miles before changing your oil is a very bad idea and represents sheer laziness. So is not changing your oil filter and drain plug compression gasket every time you change your oil. Sure you can spend extra on some oils like Amsoil which has a 15,000 mile recommended change interval, but I'd take a clean conventional oil over a dirty synthetic any day. I stick to the regular 5w30 Castrol that the dealer puts in the Prius when they do oil changes. Mobil 1 is an excellent synthetic that personally I don't use in the Prius. I reserve that for the vettes and camaros in the driveway. Even then with a good synthetic like that I personally change it every 5-7k miles.

 

Well, having the dealer change the oil could be considered lazy. (Just kidding, I realize you didn't say that you let the dealer change your oil though.) And with the time involved taking it to dealer, it is less disruptive/quicker to do it oneself.

Since the Prius engine frequently stops and starts I would be inclined to use a better quality oil in it first.

Thinking back, I don't recall of any reported Prius ICE failure/problems due to extended oil change intervals, but I do recall a couple related to problems due to the oil changes (overfills, leaving the plug out, etc.) I wouldn't be surprised if over the average vehicle lifetime in otherwise identically maintained vehicles if there was a greater chance of damage from more frequent oil changes than extending the interval within reason--perhaps 10,000 rather than 5,000 miles. 5,000 is definitely much shorter than what the oil is good for unless one has it firewalled most of the time.

 

My bad. To clarify, I do take the Prius to the dealer to get the oil changed. I would change the oil on it myself like with my other cars and probably use a synthetic blend instead, but I usually get coupons in the mail where I can get a conventional oil change that costs about as much as the materials required ($15 when I got it changed on Mon.)

You do make a good point in the second part of your post Shawn, vehicle maintenance is susceptible to human error just as much as the next thing. However when I have the dealer change the oil they are responsible for the work that they do on the vehicle. From personal experience when I change the oil on my other vehicles I don't make mistakes as decribed because I tend to be through with the work I do, and will check the filter and drain plug for leaks for the first 100 miles or so. Nonetheless, your point is valid, and those that attempt to change their oil on their own and aren't as mechanically inclined and seasoned at performing basic maintenance, and dealers with lazy technicians can make those mistakes.

Most will consider a 5000-7000 or 7500 mile interval to be a little short for Mobil 1. Even though there are bigger purists than me. I tend to be anal when it comes to preventative maintenance with the cars I use it in... you may even say that I enjoy changing the oil in those cars And at roughly $30 for 5 qts of M1, an AC Delco filter, and a comp. washer I don't mind.

 

There are quite a few cars in the EU that have an 18-24 month, 18,000-30,000 mile oil change interval. That is using a high quality ACEA A3/B3 rated oil, along with specific manufacturer long life oil ratings

Here in North America, we can't do that. Under the eyes of the API, all oil is exactly the same. It only has to be "good" for 3,000-5,000 miles, doesn't have to prevent cold black sludge, etc

If used oil analysis confirms it, its fine to go longer with oil changes. The Prius in the EU has a 12 month or 10,000 mile interval running ACEA spec oils, when I ran my Prius that long on Mobil 1 0W-20 the lab report came back fine

In the end, it's not about being "cheap" using a quality synthetic and running longer intervals. It's cheaper to get bargain basement generic oil and change it twice a year or every 5,000.

But you can usually get *better* protection, and generate a lot less used oil stream, by running a quality synthetic and extending intervals

 

Not true, Amsoil Signature 0W-30 is ACEA rated and is intended to be used up to 25000 miles with their filter.

I have been using 0W-20 in my 04 group 9 Prius for winter and just switched over to the 0W-30 because I was smelling fuel in the oil at 8800 miles. Analysis confirmed 2.8% fuel. I noticed the fuel in the oil when the weather turned VERY hot. The Amsoil filter is an EAO-09 if you want the higher capacity filter you can use the EAO-10.

 

That is 8800 miles on the oil. My Prius has 42k miles on it.

 

Not true.

AMSOIL - Signature Series 0W-30 100% Synthetic Motor Oil (SSO)

Amsoil is *very* careful to say their oil is "recommended" for such service. They do not appear to have the API "starburst" or ACEA certification on the can, indicating the oil is API or ACEA approved

Now, personally, I think Amsoil makes some very impressive oils, especially the 10W-40 AMO for classic cars with solid lifter pushrod driven valves, the oil has very high ZDDP to prevent cam lobe wear. Their diesel engine oils are also very high quality

API "starburst" certification is expensive, and fairly worthless. The Europeans had thermal oxidation guidelines over a decade ago that are barely being met now with the TEOST (Thermal oxidation Engine Oil Simulator Test) standard

You will probably be fine putting on the recommended oil change interval running Amsoil 0W-30 SSO. But that oil is *not* API certified. In the event of a problem, Toyota would have an easy out by claiming you'd voided the warranty, running an non-API oil.

Amsoil does have their own warranty. What happens if its a hidden manufacturing defect? Say a defect in the crank or con rod? It suddenly lets go, and the rod pokes out the bottom of the oil pan.

You could have changed the oil and filter daily, and it would not prevent such a failure. Amsoil may very well say "it's a manufacturing defect, go to Toyota," and Toyota would say "TFB you didn't use an API oil, so KMA you're SOL"

It could turn into a real pissing contest

That said, I wouldn't be afraid of Amsoil. I'm put off by their Multi Level Marketing approach to sales, but I do feel they offer good oils

 

Odd how with my Prius, even going 12 months and up to 10,000 miles, 0.5% fuel. So not all Prius load up the oil with fuel

 

2.8% is the highest fuel load I've seen reported so far for the Prius and is starting to hit levels that suggest something is not right. At that level its going to begin thinning out the oil noticeably.

So the question that I have is the high fuel reading the result of the oil viscosity selection, some other problem with the vehicle (e.g. blowby, injector leak, PCV blockage), both, or something coincidental?

 

Good question. There doesn't appear to be any rhyme or reason. The Prius with higher fuel in oil are relatively new, blowby shouldn't be an issue. There would be obvious signs (Blue exhaust smoke, oil consumption, etc)

PCV block might be a factor, but if that Prius was from a warm climate, sort of iffy.

Most Prius appear to have the "puddle" in the intake manifold. At first I assumed it was oil. Dipped a very long swab into the puddle and sampled the old fashioned way, with my nose. Seemed to be how gasoline would smell if allowed to evaporate and heat up, eg put some gasoline in a bowl, leave outside (But out of the rain) for a week or so. The brownish glop that eventually remains reminded me of what I found in the intake

Also interesting how despite most Prius having the puddle, only a few of them have excessive fuel in oil. We need to do a more controlled examination of those Prius cars that have fuel in oil

 

OK I see right where you are coming from. I have been an Amsoil dealer since 1997 and never noticed that. Looks like their marketing works, on dealers too. I will check into this Monday and get back.

 

I am concerned. At 6000 miles (Use) I showed less than .1% at 8000 miles I showed 2.2% a re-check at 8800 miles showed 2.8% at which time I switched to 0W-30. While I hope it was JUST the oil I have concerns it might be something more serious. I am at 500 miles on the 0W-30, have taken a sample and will send it out today. I'll let the group know results, hopefully wed or thur.

 

That's why I like used oil analysis, otherwise you'd never know what was going on. Say a very slow coolant leak that if caught early, doesn't do any damage

 

I strongly recommend against waiting 15K miles to do an oil/filter change on a Prius. I just think it's penny-wise, pound-foolish - regarding money, environment and your time. As noted, the dollar and eco cost of replacing an engine or car, or the emissions of a motor that has worn rings and cylinder liners is significant.
Surprisingly, modern Porsche engines specify 20K miles for oil changes BUT they burn a touch of oil at startup, and you'll probably add a few quarts in that 20K period. Thus you end up with a significant amount of fresh oil over the period. That said, I change the oil every 5-8K on the Porsche. Just makes good sense.
The 'problem' with the Prius is that it just doesn't burn much oil. Only a problem in that whatever you put in there on day 1 of your oil change stays in there, undiluted, for the entire oil change interval.
And as another post mentioned, Mobil 1 is incredibly good - as are a number of lower volume oils. It's not an issue of oil breakdown. Rather there are quite a lot of chemicals and particles that will build up, albeit in suspension, over a long oil change period. Though the Prius motor is the most unstressed motor I've ever seen (managed by the CVT) 15K is a very long time.
I also am not a fan of paying for an oil analysis. Unless you have a very high performance car your money is better spent doing a more frequent change. I understand it might be a thoughtful eco-technique, but I guess I'm not that far over. In order of better to worse maintenance:
1. Mobil 1 (or equivalent) and K&N filter every 5-8K miles;
2. Non-synthetic and basic filter every 5-8 miles;
3. Mobil 1 and K&N filter for 10-12K miles - with a filter change at 5-6K miles
4. Walk or bike. But don't drive.
Oh, and a drive in oil change place? Just say no.

 

The Prius in the EU has a 12 month or 10,000 mile oil change interval. Toyota vehicles here are half that

What I like about used oil analysis is that you have a very good snapshot of what is happening internally. I had no issues going 16,000 km with M1 0W-20

But say you develop a very slow coolant leak. UOA will pick that up, before the engine sludges up

 

All good points. No doubt that the analysis is a value add. Just seems a bit over the top for me. FWIW (though I doubt this would catch the slow leak you cite) I do spend a few moments examining the waste oil before putting it in the recycle container. The top layer after it's drained and cooled, and the residue after I've poured it from the catch pan in to the container can tell a story or two. Coolant separating out, excessive metal shavings, bad color. Again, not as good as a professional test, but still worth doing.
OBTW, I always use latex gloves when doing any work on the car, including waxing. Most chemicals that are good for the car can be tough (or worse) on your skin. But it sure looks goofy to people driving by my house...

 

All oil gets dirty. I have changed mine for 40 years every 2K and 3-5K for synthetic (probably too often for you guys). Before oil filters my dad changed it every 1K. Also he always ran straight antifreeze in the radiator. He managed 300K on the cars he owned/ what a record! As long as you use distilled water with straight antifreeze (most antifreeze has a large percentage of water in it anyway) you should be ok. But I still prefer mine straight up with no ice and water.

 

everyone has interesting points. ive owned a lot of performance cars and just fairly high end cars. one of the reasons i use good oil after break in is peace of mind. im not using the cheap stuff. nowadays,though, even the non synthetic oils are pretty good. remember this is an extremely high performance engine what???? well remember when it starts its at about 3 to 4 times faster than most engines instantly. also note that the prius has a 13 to 1 compression ratio!!!!. thats much higher than my boxster and even my v rod. anyway ill just continue to do 5ooo mile changes and use a good synthetic like mobil 1. i also will use the dealer since they will back up any mistakes. i remember when some independents would not even chang prius oil because they were afraid of them. not kidding.

 

Ditto on the Mobil 1 0W30. Good stuff so far and available at your local Wal-mart.

13 to 1. Makes you wonder about blow-by with very thin oil.

 

Antifreeze diluted 50% with water has greater capacity to absorb heat than undiluted antifreeze.

Note that the pink Toyota Super Long Life Coolant is already premixed with 50% distilled water. Although a gallon of SLLC contains 50% inexpensive distilled water, it still costs >$20 per gallon...