recommended oil for 75k M42?

[carnurd]

You are mostly correct, except pressing the clutch pedal in causes a forward-pushing force on the crank. But yes, pushing the clutch in when starting the engine puts hundreds of pounds of force on the half-side thrust bearing when there is no oil pressure and minimal residual oil between the crank & thrust surface. Once the car is up & running, you have the oiling system up to its minimum operating pressure and oil is pushed into where it needs to be.

Now, it is a relatively simple matter to fix this whole issue. To the best of my knowledge, you can actually put in a full 360 degree pair of thrust bearings without any mods to the block. Ask around on here and M42Club. A few guys have done this alreadyh. My M42 has this mod as well, but it was done by Metric Mechanic as part of a full engine build, so I am not 100% clear on which parts to use.



Nice. Even modern mineral oils are really good lubricants, compared to stuff 20 years ago. You are probably saving the most on oil out of any of us...it costs me like $47 for 5qts of synthetic!

Just as an aside:
Never, EVER use synthetic oil to break in an engine. The rings will never seat to the cylinder walls, and you will have poopy compression and burn oil forever. Use cheap mineral oil with a label that says it includes detergents. And always get the cylinder bores re-honed when replacing piston rings so that they can wear-in together. I only mention this because I read about a few M20 guys assuming that synthetic oil was "better" in all aspects, and used it for break-in with bad results.

I change my oil a tad more often than 3k miles but then again my car see's majority of its life 4-7500rpm on a racetrack in 100deg heat which is far more demanding than just putt-putting around and I am overly cautious(not a bad thing) when it comes to engine longevity. Also the 360Deg thrust bearing is a FACTORY replacement IE if you go to pelican parts and buy a thrust bearing for a m42 it will ONLY BE a 360deg bearing. No machine is necessary just plop in the new bearing and you are good to go.

When my head cracked due to a broken coolant connection on the plastic coolant tube on the driver side of the block. Pulled the engine and while rebuilding noticed how f#$@ed the thrust surface was on my crank. Ended up having the crank professionally welded and nitrided by a engine builder out of NV that normally builds NASCAR and SCORE/BAJA engines. Nitriding is necessary when any crank welding work is done as it is a forged piece(when you weld on a forged item you decrease the strength of the item which is where nitriding is used to re-harden the surface of the item). On top of that I replaced all the timing components as 190k miles definitely was showing a bit of wear(timing gears were sharp at the peaks where as new they are very much rounded).

Since I am running upgraded cams(279/276deg with 11.5/10.95mm lift) and the pounding that lifters take directly from the camshaft, I have been using 10-40w high zinc Amsoil. At $10.50 a quart it isn't the cheapest thing around, but I don't want to have a bearing failure or flatten out a cam lobe. Especially since this car is just a dedicated track car now.

Also running a synthetic for break-in is a HUGE no no. I have had a few engines rebuilt(american v8's and import 4's) and religiously use the most basic oils with the least amount of anti-wear additives. It allows the rings to seat properly, and with synthetic you have a much higher chance of having long term blow-by.

[Simon S]

good shit in this thread..

[carnurd]

good shit in this thread..

We try...

[Threehz]

I run 10w30 Castrol GTX, it has a good amount of zinc and overall the best characteristics of any mineral oil I've found.

Synthetic is all the better to minimize wear.

One thing to keep in mind when switching oils is how variable they are in their "anti-leaking" properties. All motor oils have a component in them which makes the gaskets and seals in the engine swell. The difference can be drastic enough that switching oils will actually cause leaking.

Just an FYI :D

[Vivek]

For those running less than 20-50, how much do you burn?

[M3Philipp]

For those running less than 20-50, how much do you burn?

I ran 10w40 half synthetic at first, later I switched to 5w40 full synthetic.
The engine took around 0,8litre on 1000 Km.
Then with the full synthetic 5w40, it took less oil.
My personal result then was it also depends on the quality of the oil itself.

Opinions about that?

What are the main reasons especially on the M42 to burn oil?
My guess or thoughts are: Cylinders are worn out in the top end, I mean the diameter becomes to high.
First because of the explosion, second because of the tipping of the piston.
That for example was the case on my M42 when I meansured the cylinders as the engine was taken apart.

And the seals of the valves in the cylinderhead (you guys know what I mean? I dont know the english word, maybe someone can tell) are worn out.
So the piston pulls oil out of the cylinderhead everytime it sucks.
The higher rpm you drive, the oil usage will increase exponentially.

[unevolved]

And the seals of the valves in the cylinderhead (you guys know what I mean? I dont know the english word, maybe someone can tell) are worn out.

You were right, they're called valve stem seals.

[HarukoE30]

The whole "change your oil every 3000 miles" thing is nonsense and has been proven as such many times over the years. Even OEMs are bailing on that nonsense in their service schedules. Many modern synthetic oils say right on the bottle that they are good for 15k miles. You are just throwing money away if you change it every 3k-5k miles. Oil does not break down in that amount of time, it just gets contaminated with cylinder blow-by and whatnot. Unless your rings are completely shot to hell, you will not suffer viscous breakdown from contamination on a street engine. Modern synthetics are really good lubricants and as long as you keep a decent filter in there you will have no issues. Many people change it frequently anyway by assuming, "better safe than sorry" but it is still sort of illogical nonsense to do so.

At this point, a lot of m42's are failing because of the overly complicated timing chain system coming apart, and a head crack between cylinder #2's exhaust valves. I have yet to see one die as a result of not changing the oil often enough or anything remotely related to that. I have owned & modded M42s for 12 years, and founded M42Club, so it isn't like I am puling this out of my ass. Your M42 will die someday from a timing chain failure or a cracked head, most likely. Well, that or a shot thrust bearing. The stock design was weak sauce in that they only put in a half-shell with a thrust surface and a lot of guys are seeing large amounts of end play in their crank. You can mitigate this by NOT pressing the clutch in when starting the car since all that does is put a bunch of force on the thrust shell when there is no oil pressure.

Also, the spec for the M42 is 20W-50. It says so right in the owner's manual.

It's great that you mentioned this, because it's the one thing right now that would destroy my 272K mile engine. Everything else is sound from Ryann (r3v-member) doing a check on the engine. I'm actually going to tear it down to do the 360 thrust bearing either spring or summer.

[djmossm42]

Also, the spec for the M42 is 20W-50. It says so right in the owner's manual.

Yes there is actually a chart in the manual with a number of oil options based on the predominant ambient air temperature. I got the manual with my car including the cassette tape lol.

[roguetoaster]

Yes there is actually a chart in the manual with a number of oil options based on the predominant ambient air temperature. I got the manual with my car including the cassette tape lol.

Doesn't the manual basically spec 20w-50 for the entire set of operating the car is likely to encounter outside of a desert or the arctic circle? Either way I run 10w-40, 20w-50, or sometimes a mix of the two, and really only base my choices on what decent full synthetic oils are on sale.

I have also noticed when I the dipstick shows about ~.4qt low if I add more I just end up not having it at the end of the week. Whereas if I leave it ~.4qt low on the stick I burn essentially none on a 250k+ mile bottom end with a replaced head with 20k on a rebuild, and I don't drive the car gently.

[Dj Buttchug]

rotella brah

[Vivek]

Doesn't the manual basically spec 20w-50 for the entire set of operating the car is likely to encounter outside of a desert or the arctic circle? Either way I run 10w-40, 20w-50, or sometimes a mix of the two, and really only base my choices on what decent full synthetic oils are on sale.

I have also noticed when I the dipstick shows about ~.4qt low if I add more I just end up not having it at the end of the week. Whereas if I leave it ~.4qt low on the stick I burn essentially none on a 250k+ mile bottom end with a replaced head with 20k on a rebuild, and I don't drive the car gently.

I remember reading that if you add any more oil than is necessary you'll likely burn it all up quickly.

[lolcantturn]

I am running 5w-20 in my M42, and in 7000 miles i only burnt less than half a pint of oil and that's because I was hauling cargo up a steep ass hill at 5000rpm for two miles.

[roguetoaster]

I remember reading that if you add any more oil than is necessary you'll likely burn it all up quickly.

Agreed, was just suggesting that maybe there is some inherent dipstick inaccuracy.

I suppose the best advice on oil is get a full synthetic that is on sale and if the car burns it up just go to a heavier grade (within reason) until it stops consuming oil.

[jntar]

Mobil 1 High Mileage 10-40 motor @ 209k. I burn/leak around 1/2 a quart every 6-7k miles so I change it around that time.