Break in period - cruise control

[adgjqetuo]

Taking a 12 hour trip tomorrow, she currently has 1,800 miles, anyone think using cruise control will be a problem or should I be past that point by now?

[Aorys]

I never saw anything in the owners manual about not using the cruise control. It says not to run the same speed "for a long period of time" during the first 1000 miles.

I used the cruise control during the first 1000 miles, adjusting the speed occasionally (every 15 minutes or so).

You are definitely fine now at your mileage.

[JAvendan]

agreed... you should be good to go!

joel

[JustMatt]

Not keeping the same speed in a vehicle for the first 1000 miles is an excellent idea ... for your carbureted vehicle. According to my "other" boxer engine dealer, this had less to do with maintaining the same speed, and more to do with breaking in the spring(s) and mechanics associated with the carburetor; generating a "flat spot" half way through the throttle opening (from closed to WOT). Drive-by-wire (throttle, at least) as pretty much done away with this.

I think a lot of legacy information has been passed down from generation to generation without substantiating whether or not it is actually necessary... sort of like changing your oil every 3,000 miles.

Besides, unless you live in Texas or some other incredibly flat state, you're probably going to be varying engine speeds @70MPH on a 12hr trip as you ascend/descend hills, go through stoplights for pee breaks, etc.

[G-Omaha]

Issue is probably more centered on the rings than on the fuel delivery system. You do know that these are fuel injected?

[Tom28]

Book said something about 500 miles. Dealer said 1000.

Either way, you should be good to go at 1800.

[AO River]

^^ Owner's manual also says 1,000 miles. OP should be good to go at his current mileage.

[JustMatt]

Originally Posted by G-Omaha

Issue is probably more centered on the rings than on the fuel delivery system. You do know that these are fuel injected?

Yes, perhaps I didn't make it clear. This advice was great advice to give when you had a carbureted vehicle. Having not seen one of those since the 80s, it's legacy advice; it is outdated and should not be offered anymore.

IDK about Subaru engines specifically, however many others are "broken in" at the factory; some prior to mating with their chassis.

Here's an article from the late 90s discussing the piston ring theory. It seems more related to higher engine speeds vs. cruise control.

[Healey3000]

Originally Posted by JustMatt

Not keeping the same speed in a vehicle for the first 1000 miles is an excellent idea ... for your carbureted vehicle. According to my "other" boxer engine dealer, this had less to do with maintaining the same speed, and more to do with breaking in the spring(s) and mechanics associated with the carburetor; generating a "flat spot" half way through the throttle opening (from closed to WOT). Drive-by-wire (throttle, at least) as pretty much done away with this.

I think a lot of legacy information has been passed down from generation to generation without substantiating whether or not it is actually necessary... sort of like changing your oil every 3,000 miles.

Besides, unless you live in Texas or some other incredibly flat state, you're probably going to be varying engine speeds @70MPH on a 12hr trip as you ascend/descend hills, go through stoplights for pee breaks, etc.

I suppose the carb flat spot theory is valid but there are still reasons for not driving at a constant speed.

Regardless of the fueling method, varying the load while driving causes thrust loading on the crankshaft and pistons. Allowing new rings to thrust forwards and backwards causes them to "seat" in the bores. Driving at constant speed generates little thrust loading and cylinder bore glazing can take place as a result. Once glazed, it causes poor oil sealing and the engine wil be prone to burn oil from then on.

Modern engines are built to much tighter tolerances and don't need as much break-in but they do need some. As to changing oil early after break-in, I agree that finding metal shavings in the oil is a thing of the past but manufacturers still use assembly lube when they build the engine. I prefer to remove this lube once it mixes in with the oil. Call me old fashioned, or legacy-minded but I go by the simple maximm that an early oil change doesn't hurt and since I keep my cars for a very long time, I'll do whatever it takes to extend the engine's life.

While the OP is past the break-in mileage, it wouldn't hurt to now and then disengage cruise, apply a healthy does of accelerator for a bit and back off, doing this three or four times. I remember an engine builder I spoke with who elieved that the best way to break-in a new engine was to put it in second gear, go full throttle and back off to low RPM, followed by another run. Five or six such runs produced engines that burnt no oil.

[mcbrew]

I have found metal shavings in EVERY break in oil filter I have opened. This includes VW, Mercedes, Toyota, and Subaru. Still happens... Every time.