Question for fuel dilution

[toyotapriusguy]

So I have a 2007 prius, and usually drive less than 5 miles at a time. When I do park, it's for hours so the engine cools down completely. Obviously my oil NEVER gets very warm in the 10/15 minutes that I'm driving. I've always run M1 at 5k OCI's bur recently decided to run almost 9k because of a 5,500 mile road trip and those highway miles being so easy on oil.

SO my concern was that since I'm sure I get a fair bit of dilution, and I ran it 5.5k already, how long do I need to drive down the interstate to get the oil nice and hot and try to boil off an much of that fuel and water as possible? I did 120 miles of interstate today, 60 miles in the morning and another in the evening. Think that's enough? I don't have an oil temp gauge

 

[Spyder7]

I think you might be misunderstanding the fuel dilution aspect and how it works. Fuel dilution is a contaminant that builds up slowly from mostly, or almost exclusively, short trips, and which is not something you burn off just once and all is well with the oil again. It doesn't really work that way.

If you put say 5k of exclusively short trips on the car, then it doesn't matter how long you run it to burn off the fuel present - the contamination (and resultant oil breakdown) has already occurred and a highway run of any distance to burn the fuel off (and moisture as well, for that matter, since its second to fuel as a common oil contaminant and occurs along a similar process) won't turn back the clock on the oil or in anyway "restore" it.

To effectively deal with moisture buildup and fuel dilution, there are two typical strategies:

1. From the day you have the oil changed, make sure the car is run long enough to get up to operating temp. In your climate, a 15 minute drive once a week on the freeway would suffice as a simple example. This burns the fuel and moisture off before it accumulates, and prevents the oil from becoming fuel diluted and the resultant breakdown and shortening of the useful lifespan of the oil.

2. Simply follow what your owner's manual recommends for severe service oil change schedules and stick to it (typically this is 3k/3 months but varies some). Short trips like you describe is definitive severe service so you follow that schedule if option A isn't appealing or something you can't stick to (or an equivalently regular trip of long enough duration to get the engine to operating temp).

-Spyder

 

[toyotapriusguy]

Well my owners manual says 5k OCI, but the TSB they put out for 0w-20 synthetic on the gen3 with the same power train as my gen2 was 10k OCI

I realize that the fuel itself does it's damage once it's there. However, I was thinking that getting the fuel and water itself out might help. You say to run it once a week down the freeway, well I changed the oil 3 weeks and 5,900 miles ago.

I'm not trying to "restore" the oil, I just wanted to simply get the water and fuel out.

Thanks Spyder

Richard

 

[Spyder7]

If you put 5.9k on in the last 3 weeks then no need to worry about effects of any fuel/moisture buildup as you've put more than enough miles on in a short enough span that its presently a non-issue. In your climate, to keep it that way so as to extend out your OCI effectively, just get it up to operating temp regular. "Regular" in this context typically is once a week; operating temp in your climate would be reached long enough after about a 10 minute freeway run.

The original 5k recommendation and new 10k TSB modification is assuming you are using the vehicle "normally" rather than in "severe service." What you initially describe - trips exclusively that are of 5 miles or less, is severe service because that driving pattern means the oil is never getting up to operating temp, and moisture is accumulating more often and fuel dilution becomes an issue. This gradually contaminates the oil and shortens its useful lifespan. Your owner's manual should list a severe service OCI, and usually it is 3k/3 months.

Note that these are two separate points. The first is avoiding fuel dilution; the second, the relevant OCI to follow if avoiding severe service is not possible or desirable.

-Spyder

 

[demarpaint]

A long run certainly will help, however due to the fuel and water the oil 'wears' for lack of a better word. That's just another way of saying what Spyder already mentioned. The only real way to tell the condition of the oil, and if a weekly freeway run is helping would be to take a sample of the oil, via the dipstick and send it to a lab for sampling. Anything else would be guessing at best.

Is their 0W20 10K mile OCI for severe service use? Your driving habits puts you into SS use category.

 

[toyotapriusguy]

Honestly Spyder I've looked through my Owners Manual, Scheduled Maintenance Guide, and all that other fun stuff and it just flat out says 5K

.

I can make a run down to Santa Monica once a week or over the hill to North Hollywood and back until I change my oil. This is the only oil change I'm extending beyond 5k because I'm still in warranty and don't wanna ruffle to many feathers if I ever have a warranty issue.

As a side note, when we lived in Palm Springs the dealership there set the MFD to alert me every 2.5k for an oil change. They said because of the extreme summer temps that even with M1, it wasn't safe to run it more than 2.5k miles. Wish I knew then what I know now. Would have saved me $1,600 in oil changes!

Richard

 

[chubbs1]

Originally Posted By: toyotapriusguy
As a side note, when we lived in Palm Springs the dealership there set the MFD to alert me every 2.5k for an oil change. They said because of the extreme summer temps that even with M1, it wasn't safe to run it more than 2.5k miles. Wish I knew then what I know now. Would have saved me $1,600 in oil changes!

Richard



What a bunch of @*#&%*&%!!
If you HAVE to get oil changes at 5k anyway, don't worry too much about the fuel dilution and going out of your wat to do extra driving. Just change at 5k. When/if you decide to extend, follow the advice by spyder and Demar and do a UOA at 5k and see where you stand. Extend from there.

 

[goodtimes]

They say 10k on the 2010 models, and a lot of folks don't know one size doesn't fit all. 2010 owners,not folks here. The Prius you have has the thermos bottle for faster warm up, but still, the laws of nature are at work.

It's a good question. Fuel mixes with oil, but when it burns off, is it a separate entity as before, or has it reacted with oil molecules and altered the oil? I would guess to say it has reacted. Water we know doesn't go in solution with motor oil, so when it is burned off, the oil should be the same.