OK wHAT HAPPENS IF YOU PUT IN 4 QUARTS OF OIL?

little less MPG. 3.75 would be good.

 

Engine oil capacity w/filter change on a 2010 Prius is 4.4 qts. With 4 qts, you should see the dipstick level about 2/3 from the bottom.

 

Yup, posted in the wrong section of the forum. Perhaps a mod. will move this for you.

Second gen. -may- experience a slight drop in mileage with a bit too much oil, but 4 qts. may be ok for a 3rd gen.

 

I doubt that you will see any change with such a tiny change in oil level.

What might be more interesting is if you were to monitor your mpg with 3 quarts of oil in the crankcase, and see if there's any improvement. That will still give you an oil level above the bottom dimple on the dipstick.

 

You might get a big bill down the road for replacing oil seals. Most dipsticks clearly warn: Do not overfill.

 

3.9 quarts is the dry system capacity. At an oil change 3.5 quarts will fill the system including the filter. Three quarts exactly works just fine. Try it.

It may not damage any seals but even a little overfilling has been found to start fouling the MAF. That can reduce fuel economy drastically.

 

No matter how many fuel tanks you go through, there is enough variability from tank to tank that such a change will ever show up, if it is in fact a real change. You just cannot get a good feel for MPG even if the level, whatever you have it at will remain the same from tank to tank. Urban legends

 

In reality, you wouldn't cause any damage. BUT it'd be a good excuse to refuse any warranty claims, if you have a shady dealer where you live.

After all, even if it was only extremely minimal overfilling, they'd legitimately have a point that it was overfilled.

 

FWIW, my 2008 Prius was overfilled (~3/16" above the full mark) by the factory and again by the dealer at 5,000 miles. This seems to be common practice by many Toyota dealerships.

IMHO, Toyota would be on very shaky ground trying to deny a warranty claim for this reason. They tried this with the engine sludging problem a few years back and lost big time!

 

3 quarts *is* sufficient for a drain/refill and filter change in
a second-gen, placing the level somewhere between the marks on
the stick [duh, like we were taught to check for back in the day]
but on the lower side of that range. The third-gen takes a little
more. Most of my changes are less than 3.5 quarts these days, and
I keep an eye on it for any need of a top-up but it doesn't seem
to lose any at all between changes. Mostly filling the new filter
before putting it on helps re-establish circulation a little
faster at startup.
.
_H*