Break in speed for new Prius

[blackprius2007]

Can someone tell me if I am suppose to maintain or stay below certain speed/RPM for new Prius for certain number of miles in order to break in the engine? I know for regular (non-hybrid) cars (like camry, accord, etc) one should not exceed over 55 mph for the first few thousand ( 1,000 to 2,000) miles. Wondering if there are any restrictions as such for Prius hybrid vehicles.

[Bill Merchant]

I think it's in the front of the Passport maintenance manual, not sure. In essence, don't drive like a jerk for at least 600 miles, no jackrabbit starts, no testing the ABS unless you need to. Since the computer controls when and how fast the Internal Combustion Engine runs, you don't have to baby your new baby, just treat her nice. Try to stay under 70 mph for the first 600 miles. Your MPG will be better that way too, but don't worry about getting super MPG for a while. Just drive and enjoy, learn your car.

And welcome to PriusChat, GB!

[acdii]

Take it from me, I was an ASE certified mechanic, and have tons of experience working on engines. The break-in period for a new engine is 500 miles, that is to seat the rings to the cylinder walls, and nothing else. From what I have gathered so far with the Prius is the break in period is just a bit longer, 600 is correct, but the engine doesnt rev as high as a normal engine, so driving up to 70 is OK, dont exceed it for at least 1000 miles. DO NOT under ANY circumstances maintain a steady speed, vary it a LOT. THis is what helps seat the rings. Basically, when I rebuilt an engine, (Havent touched one in years, bad back) after it was installed and tuned up, pressure checked and OK for the road, I would take it out on a long strecth of empty road, gun it to 50-60 MPH then coast. I would do that 10 times to seat the rings. Once that is done, then no heavy accelerations for the first 500 miles and alway vary the speed. I am not sure how the factory does it, but they seat the rings in a similiar fashion. After the initial 600-1000 miles, drive it like you stole it. Unlike engines of yesteryear, todays engines have very high tolerences, machining is damn near perfect, and variances are practically nil. This is mainly why you no longer need to change out the oil after break-in like with a rebuild, or earlier cars. Alos, factory oil tends to have special modifiers in them to help ensure a clean break-in period, not neccesarily the oil itself, but the lubricants that were used during the build of the engine, like moly prelube, graphite, lubes of that nature.

If you ever have a chance to see a brand new engine being made, do it, it is interesting to see how they are made, majority of it is done by robotics now.

[donee]

Hi All,

The Prius HSD will vary the engine RPM, and use electric assist automatically, even at a constant speed, as long as there is some variablity in the driving conditions. All this variability needs to be is a slight upgrade, or downgrade, passing trucks , shifting winds, overpasses blocking, or aiding the wind.

So, unless your in a windless salt-pan deasert, or eastern Oklahoma (dead flat!), your probably OK to run at a constant speed (NOT Constant RPM) with the Prius during break-in.

[Bill Merchant]

<div class='quotetop'>QUOTE(Bill Merchant @ Apr 22 2007, 11:56 PM) [snapback]428213[/snapback]</div>

Since the computer controls when and how fast the Internal Combustion Engine runs, you don't have to baby your new baby, just treat her nice.[/b]

[alexstarfire]

Not to sound like a newb or anything, but what'll happen if you break it in wrong?

[acdii]

<div class='quotetop'>QUOTE(Alexstarfire @ Apr 24 2007, 01:51 AM) [snapback]428886[/snapback]</div>

Not to sound like a newb or anything, but what'll happen if you break it in wrong?
[/b]

It is a bit difficult to improperly breakin a new engine in todays cars, but what can happen is if you over rev the engine, you can cause the rings to break, sieze, score the cylinder walls, crack a piston, etc. The engine will not seal properly and it will burn oil. Bearings, guides, seals etc dont need a break in period, camshafts/lifters OTOH do. The area that the lifter rides against the cam will need to wear in a bit, but the main item that requires break in are the rings, it takes a while for them to wear sufficiently to the point where they sit against the cylinder walls and give the strongest seal. Rings flex with the up down motion of the piston and need to wear the edges smooth so they seat. Those are really the only engine parts that move in such a manner, the rest basically dont move, but have a thin layer of oil seperating them from each other.

BTW, one other poster mentioned the PCM controls the engine speed, this may be true, but not enough to properly break in the engine. Variance in speed means good acceleration/deceleration, which the Prius wont do by itself, the variance is not enough. varying speed between 45-55 Mph is what will do it properly.

[richard schumacher]

Stomping on the brakes before they are worn in might cause the disks to warp. Drive easy the first 600 miles, just like it says in the owner's manual, and you'll be fine.

[daniel]

Bill Merchant is correct. ACD is talking about conventional cars, where there is a fixed ratio, for any given gear, between engine RPM and vehicle speed. There is no such fixed ratio in the Prius. Richard is correct about the brakes.

Read the owner's manual and do as it says.

[Charles Suitt]

Former comments are right. Look at page 318 Owner's Manual.