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What is GM's LT4 break-in oil - First oil change miles?
I know what the manual says, but on other cars I have had good luck with the escalated break in procedure. Getting the motor well loaded within the first 100 miles. Then changing the oil. I am not wanting to start a debate on that subject.
What I want to know is if anyone knows for sure what oil or additives GM uses for the first fill? Is it a special break in oil or just regular Mobil 1? Maybe some of you that have done the motor build program know.
I remember reading back in '15 that no special additives were added for break-in. It might have changed since then, but I know that most manufactures have stop using break-in additives years ago.
No special break in oil. The 500 mile oil change isn't about the type of oil. They had some oil filter issues with the first C7s and that is how they resolve it.
The main reason for the break in period is the rest of the drive train. The transmission and rear axle need to be broken in as well. The engine is broken in during production and there isn't any need for special break in oil like they had 60 years ago.
No special break in oil. The 500 mile oil change isn't about the type of oil. They had some oil filter issues with the first C7s and that is how they resolve it.
Actually Bill, that's not correct. The issue with the 500 mile oil change is that silicone from the RTV they use in the engine assembly leeches into the oil and froths up. So take it easy for the first 500 miles (to avoid the frothing) and then change that oil as quickly as you can.
No special break in oil. The 500 mile oil change isn't about the type of oil. They had some oil filter issues with the first C7s and that is how they resolve it.
The main reason for the break in period is the rest of the drive train. The transmission and rear axle need to be broken in as well. The engine is broken in during production and there isn't any need for special break in oil like they had 60 years ago.
Bill
How do you know the engine is broken in during production? What I remember seeing, but I could be wrong, is they have a machine that turns the engine over with spark plugs out. It's not run on combustion so there is no cylinder pressure to seat the rings. Has anyone seen what they do during production to break in the engine?
How do you know the engine is broken in during production? What I remember seeing, but I could be wrong, is they have a machine that turns the engine over with spark plugs out. It's not run on combustion so there is no cylinder pressure to seat the rings. Has anyone seen what they do during production to break in the engine?
Every car is fired up at the end of the line and run up and down through the rev range (not aggressively) while running diagnostics on the computers to make sure everything is running right.
Aside from that, not much, except for the cars that get randomly pulled for additional QC checks and get 10 - 20 miles put on them.
How do you know the engine is broken in during production? What I remember seeing, but I could be wrong, is they have a machine that turns the engine over with spark plugs out. It's not run on combustion so there is no cylinder pressure to seat the rings. Has anyone seen what they do during production to break in the engine?
The LT4 uses moly faced rings as most all GM engines have used for over 30 years. GM also uses a plateau honing process on the cylinder bores which nearly mimics the surface finish of a broken in cylinder wall. The soft moly coating on the rings in conjunction with the plateau honing process means the rings are seated literally within about 10 engine revolutions and no cylinder pressure is required, it can happen right on the engine stand. As Bill stated, there is no need to break in the engine today, it happens during production as they turn the engine over.
Your "escalated break in procedure" works for the engine but only because ANY procedure will work. You will however run the risk of damaging other components in the drivetrain so it's highly recommended you follow the break-in procedure in the owner's manual or you may end up with a case of the "howling" rear end. The brakes take about 200 miles to seat, the tires take about 200 miles for the "mold release" to wear off, the transmission needs about 500 miles for the gears to lap in, but the ring and pinion take the longest to lap in and are the most sensitive. But for the engine, you could do anything to it within design limitations starting from the first mile and you won't hurt it...as Bill stated, the break-in isn't for the engine. In the end, it's your car and you can do whatever you want to it...good luck and enjoy!
Edit: Here's a link that speaks to the plateau cylinder honing process.
I don't recall the manual saying anything about heat cycling during the first 500 miles. What is really the best for ring and pinion? Is it best to run about 50 miles and let things cool down overnight?
What is the best for trans gears? Does the manual limit top speed? It seems like exceeding some max speed could be an issue.
I don't recall the manual saying anything about heat cycling during the first 500 miles. What is really the best for ring and pinion? Is it best to run about 50 miles and let things cool down overnight?
What is the best for trans gears? Does the manual limit top speed? It seems like exceeding some max speed could be an issue.
I don't remember the manual saying anything about "heat cycling" either but I think that term is used improperly with respect to cars. The link is a little more restrictive than the manual as it calls for stopping after 15-20 minutes of driving and allowing the differential to cool...there's nothing that says you aren't allowed to do more than the minimum. Other than that, the link follows the owner's manual closely including continued but less restrictive limitations after 500 miles...heat is the enemy. Remember, you'll have 650 HP/650 LB-FT to play with so it relates very well to the towing conditions he cites.
The manual transmission gears could be lapped in by 200 miles if you use different gears in city driving. If you do most of your break-in miles in 7th gear, it'll take longer to lap in the lower gears...and remember there are no gears associated with 4th gear as the synchro/shifting ring just locks the input and output shafts together so no need to waste any time in 4th. All gears are constantly in mesh but the lapping process only occurs with load. Varying the speed means using different gears.
And yes, speed is an issue...more speed means more load/HP which means more heat, follow the speed restrictions as best as you can. As HP levels continue to increase, the break-in for the drivetrain becomes more and more important.
I think glass_slipper has the right info on breakin. He's correct that the 500 mile oil change is not about wear (and that breakin on the cylinders is largely done before that anyway).
The factory fill (while not special) needs to be replaced by about 500 miles as the anti-foaming agents in that initial fill will have been depleted by then. Without that change you're susceptible to an oil leak.
When I built my engine we wheeled it into a room where it was loaded on to a stand. They plug an electric motor that spins the engine up tp about 2,000 rpm if I remember right. The measure all harmonics looking for issues with the assembly. Then its moved into another room where it is fully connected, air, plug wires, fuel, oil, and it is fired up, it runs for about 3 minutes, I believe it ran up to 3500 rpm, then they unplugged the exhaust for me, man did that sound good! After the car rolls off the end of the assembly line they drive it into a room and run it up through the gears, taking it up to 73 miles an hour, which is what I saw, again checking it all out. There is a long straight-away out back and I believe they drive the cars up and back before parking them for loading.
Sarah points out to me the electric motor that provides power to spin engine
Loading engine into non firing test stand
Everything connected full run up to speed, see dry sump tank on right
06-30-2017, 01:41 PM
What is GM's LT4 break-in oil - First oil change miles?
