Oil Change Question

I'm not the expert but I don't think you need to worry about the viscosity. However you may want to siphon out enough oil to get it down to the full mark at least. Too much oil will foul a sensor, throw a code, and the computer will shut down the engine. This can be quite a thrill ride if it happens on an interstate.

 

There is a TSB regarding the overfill issue you should talk with the Prius Tech. Your manual also states to use 5w/30 oil.

 

The manual specifies that the oil be changed every 5K miles. How much benefit is there to doing it more often? Sorry if this isn't the place for that question...I'm just curious as to why one would do it at 1K?

 

sure about that?

one ran with 8 qts in it... (double fill by express lube genius) no codes, no shutoff, no lights. just smoke. lots and lots of smoke.
eventually spit out a code for out of range o2 sensor reading... cleared itself after a few starts.

drained the oil, filled it right, ran in forced idle for about 45 min, smoke cleared out, all was ok.

you may be thinking of the classic prius issue where the engine won't start?

 

I wouldn't worry about the 5w20 viscosity at all. As far as the slight overfill over a long period of time several overfills will probably prematurely shorten the life of the O2 sensor, but it sounds like they put a straight 4 quarts in, giving you an overfill of less than half a quart, not much to really worry about.

 

But don't let them make a habit of it. Tell them to put in no more than 3.5 quarts, and that you will check the level on their drive before you leave. And then do it, every time (this is a good idea regardless; someone forgetting to tighten the drain plug or the filter or even merely leaving out the dipstick can ruin your whole day).

For more confidence you can bring your own oil and have them use that. 3 quarts is both convenient and sufficient because some of the old oil remains in the sump and coating the internal surfaces. In my experience three quarts always leaves the level halfway between ADD and FULL, which is plenty.

 

The oil "experts" who have had analysis done have concluded the specified change intervals are about right. So no real benefit to changing more often.

As far as an "overfill", with a full 4 qts, my personal experience shows this is a non-issue. You can get silly if you like, but 1/2 qt isn't going to make any difference, at least that I can measure, see, or experience. You have to put in several qts extra before anything "bad" happens.
I put in 4 litres with no ill effects, including on mileage. I even put in three litres of 5W30 and one of 10W30 (using up the oil I have). Oh My!!

 

My car was slightly overfilled when I purchased it. Keep in mind that the original oil in our cars was put in by the factory, not the dealership. If the dealerships are slightly overfilling, then they are consistent with the amount of oil the factory is using. (At least that was my experience).

 

Galaxee, it happened to the white 2007 Prius at the office. The car was towed to the Toyota dealer. The place that did the oil change paid for the tow, the part & the rental since it wasn't a warranty trip.

 

what part? if a part had to be replaced, it almost certainly couldn't have been the oil. you never know with some places, you know?

DH won't rule out an o2 sensor from the realm of possibilities but that's some pretty hardcore overfill to do THAT. not just 1/2 inch over the full mark.