I have been wondering if Oil sludge build up on the Prius is a problem since there is no way to warm up the gas engine. I was always told that you want to warm up the engine before driving away to preven excesive sludge build-up. Also how one drives can effect the build up of sludge (along with weather).

With this in mind and the fact that the engine turns on/off at any given time I am going to switch over to full synthetic oil after my second initial oil change.
However I am not so sure that Synthetic Oil will be any better at reducing sludge .

Does anyone have any information , comments or suggestions ??

When it's cold the ICE starts and runs till the catalytic converter and other emissions systems are up to temperature, so it shouldn't be a problem.

2005 Prius - White, Gray Interior, Option Package 6, Mud Flaps & Auto Door locks from Coastal


2006 Highlander Hybrid - Limited, White, Tan Interior, Nav, 4WD, Trailer Hitch

NOTE: On both the Prius and HH batteries are included with your purchase !

Engine oil in Prius is a major topic in several discussion groups, but I have not heard a report of sludge.

Many fewer are the used oil analyses posted for Prius. As a group, these have all been very clean. Only flagged for high moisture or fuel content when the oil sample has been obtained inappropriately (I did that the first time - rookie error).

DAS

Sludge. There's a term I haven't heard in a loooong time. Normally associated with old engines, old oil, poor maintenance. Not often heard with modern engines, modern oil, and proper maintenance.

Unless you own a Toyota / Lexus with a 1-MZ engine manufactured between 1997-2002

Because they haven't been looking at their transaxle oil. While researching cold weather performance, we changed the transaxle oil in an 03 Prius from Texas with 53k mi. and had a 'Holy ****' moment. Check out the oil analysis, silicon levels.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

where is the analysis?

Either scroll down or search for "Silicon". I need to reorganize the web page from lab format to final report. Thanks.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

You may be on to something there, with dirt entry into the transaxle breather. Will watch what you come up with. Your analytical lab does not mention the possibility that Si could come from gasket seal material, as I might have guessed.

I had this fluid changed at about 60k miles, just so they could tell be if there was any Fe stuck to the magnet (there wasn't). But now I wish I had sprung for a fluid chemical analysis.

The Prius transaxle failures known from the Prius internet groups are few (and there are others of uncertain veracity on the Edmunds forums), but AFAIK no transaxle fluid analyses have been published, other than yours.

DAS

great find! I'm always intrigued about classic priuses because it could be my next car lol... keep up with the great reports and hope that car runs forever!

i got around 20 km a liter when i drove a civic 5 spd using advanced hypermiler techniques
and now I drive a salvage nwh20 prius that gets almost to 25 km/l with 195,000 km to date.