straight6pwr said:

personally, i've never run 20w in anything.

i also believe that brand names, additives, blah blah blah is marketing b.s. and the difference in quality doesn't justify the extra costs. get the right weight in whatever fits in your budget.

Ditto.

20w- anything is an archaic spec that belongs back in the 50-60's. Only guys using it are into old muscle cars with sloppy clearances, because some of the oils are blended to protect flat tappet push-rod valvetrain.  Or they like to see 100psi. on the gauge on cold starts and think it's a good thing.  

Most older BMW engine clearances are designed to run a 10-13cSt oil viscosity. Or ~30weight oil running @100c. All oils start much thicker when cold.
Running a thicker oil doesn't make sense unless you run the oil hotter the 100c. A 20w50 will be ~20cSt @100c but it will thin to ~12cSt at 120c. engine thinks it got 0w30 in it. It's happy.
The cold end of the scale looks much worse. A 0w30 is 65cSt @40c while the 20w50 is 180cSt at 40c. It takes that much longer for the oil to warm up and flow throughout the engine.
This is not even looking below freezing. In those temps the extra drag can defeat a good battery and starter. You're trying to pump molasses through a coffee straw.
The 0w40 synthetics are a good compromise of performance and protection. With a 75cSt cold and ~13 cSt hot. It's on the thick side of spec.@100c thinning to ~8cSt @120c still giving you some track protection, without relying on the additive package to keep the bearings from seizing for 2-3 times longer on cold start.

everyone says that most of your wear comes from cold starts, so why use an oil that will take twice as long to warm to running temp.  If you need to run your oil that hot add a oil cooler, or as a last resort run a 5W-50 (115cSt cold, 18.5cSt hot). Not as a first step.

Oil analysis

Oil analysis is a great way to know engine health.  Like a blood test for your car. But, it's meaningless by itself.  You need multiple samples to get a true picture of engine health. If you put on a lot of miles and change the oil on a schedule with the same brand/type of oil,  it can save you allot in showing you true extended drain intervals for your environment/ driving style.

In a garage queen that gets an oil change every year and runs 1k mi. it's pointless unless your looking for a piece of mind. by getting a baseline and getting follow up test you can know nothing changed. on a 1million dollar car it's worth something, on a 200k mi daily, not so much.
 

Jdesign said:

This is over kill but its still cool to do though! I personally have never cared enough to do it. Do you have experience?

I don't, I never cared enough for the e30 to do it. I was also a little scared of what it'd find haha. I might for the e34 though to see what we're working with and whether there's any weird issues.

i recently did the test on 318is that I expect has well over 250k on the m42. Report came back clean which was a nice surprise.

P_Roloff said:

If you’re really worried ever, you can also send an oil sample off to blackstone labs and have them run an analysis on it, they can tell you if there’s anything amiss. 

This is over kill but its still cool to do though! I personally have never cared enough to do it. Do you have experience?

personally, i've never run 20w in anything.

i also believe that brand names, additives, blah blah blah is marketing b.s. and the difference in quality doesn't justify the extra costs. get the right weight in whatever fits in your budget.

vbhargava said:

I have an M20 with ~150,000 miles on it. Wondering what viscosity you guys use and why. In researching this online it seems everyone uses something different and ECS sells a bunch of options even when narrowing the search down to this car. 

Thanks in advance for the assistance. 

I run 20w-50 Castrol GTX, it's the recommended summer weight per the manual and Castrol I believe was BMW's recommended oil at that time. Otherwise, some people say that Valvoline VR1 in the same weight is a good choice due to higher concentration of ZDDP. I don't stress too much about it personally, I can't imagine there would be huge difference in wear whichever way you go as long as you stick to the recommended oil weights and oil change intervals.