what oil?

[jiminEcricket]

#1)i have an 89'525i (grey market) i have been using castrol 20w50 since i replaced the cam,rockers,valve springs, piston rings, all bearings about a year ago. the motor sounds kind of loud compared to other m20 motors i've heard, sounds like lifter tap,but i know there are no lifters. i have adjusted the valves twice as per bentley and it did not help. should i not be using 20w50? btw, i live in tn.
#2) has anyone had the outside temp computer (clock,etc) keep chiming from time to time and the display changing from the clock to the outside temp?(which is incorrect as i know it is not -10 c) i replaced the sensor w/a salvage yard part -no help. is this a common problem?

[632 Regal]

Mobil1 0w-40

might have a bad connection/shorting wire, mine went goofy once from water getting in there from a car wash (my kid and a hose)

[JonE]

#1)i have an 89'525i (grey market) i have been using castrol 20w50 since i replaced the cam,rockers,valve springs, piston rings, all bearings about a year ago. the motor sounds kind of loud compared to other m20 motors i've heard, sounds like lifter tap,but i know there are no lifters. i have adjusted the valves twice as per bentley and it did not help. should i not be using 20w50? btw, i live in tn.
#2) has anyone had the outside temp computer (clock,etc) keep chiming from time to time and the display changing from the clock to the outside temp?(which is incorrect as i know it is not -10 c) i replaced the sensor w/a salvage yard part -no help. is this a common problem?

1. The 20-50 should be fine, many of us have switched to synthetic and when I did, my 535 was a bit quieter and seemed to run smoother. My M20 in the 325iC has that same "valve tap" sound too. Otherwise runs great. Other posts have talked about the tapping noise and other potential causes relating to valve train wear, etc. Others might chime in on this.

2. Had the finicky outside temp sensor issue, too on the E34. It can be wiring, the connector, or the sensor itself. That area sees alot of moisture and crud so it could just be really dirty at the connection. Try cleaning the connections first.
Good luck

[cary]

For synthetics Mobil 1 0w-40 is the best all around choice for all temps and easily available. For Mineral oil 20w-50 is fine down to temps of about 40f. Follow your owners manual for weight guidlines for mineral oils.

I don't know how loud your valvetrain noise is, but on the M20 the valves should tick slightly. If they don't, they are to tight.

[mikedev10]

why 0 instead of 5/10? just got mine haven't changed oil yet :p

[632 Regal]

because its just better!

RYAN!!

Need your expertise here!

[cary]

why 0 instead of 5/10? just got mine haven't changed oil yet :p

I'm not Ryan but I will chime in and answer.

The first number in an multi weight oil (0w, 5w, 10w, 15, 20w, etc) refers to the cold start properties of the oil. The cold start properties are measured by taking the thickness of the oil in centastokes (sp) aka CST at a set tempurature. To qualify for each of the above, the oil must be thinner than certain thickness at a certain temp, as follows:

0w = less than 6200 cst @ -35c
5w = less than 6600 cst @ -30c
10w = less than 7000 cst @ -25c
15w = less than 7000 cst @ -20c
20w = less than 9500 cst @ -15c

For comparison in thickness, the second number in a multi weight oil refers to its thickness in CST at 100c and falls into the following range:

20 weight 5.6-9.3 cst@100c
30 weight 9.3-12.5 cst@100c
40 weight 12.5-16.3 cst@100c
50 weight 16.3-21.9 cst@100c


You question is why a 0w rather than a 5w or 10w? The answer is that a 0w oil flows better at startup tempuratures, including normal room temp (I have verified this from Mobil's own PDF charts that I was lucky enough to get a copy of) and accordingly gets oil to critical engine parts faster.

So the next question that follows is why don't all manufuactures just make 0w-xx oils? The reason is that Group I and II basestocks that mineral oils use, require a great deal of pour point depressants and VI modifiers to make them a wide spread multiweight, and these additives break down over time and can cause sludge and varnish buildup. Note that the quality of the additives have improved greatly over the years, so this isn't nearly the problem that it used to be and generally only an issue in certain motors that have sludge issues (Toyota 3.0L V-6 and I-4 motors from 1999-2002 for example) with low quality oils.

When you look at synthetics (Group III (questionable), Group IV & Group V basestocks), you have a base oil that due to its highly refined and homogenous nature is naturally multiweight. It is commonly agreed that for example that Mobil 1 10w-30 uses no VI or pour point depressants. Redline has publicly stated many times their only oil that uses VI improvers or pour point depresants is their 5w-40. So with a synthetic you start with an oil that is already naturally multiweight, add few high quality pour point depressants and VI improvers (example, Mobil 1's sypersyn VI improver has a VI of approx 3000, compare that to most VI improvers VI of approx 300) and you can easily make a very stable 0w-40 oil with few additives.

Hope this answers your question.

[mikedev10]

so if i'm using synthetic on my car (chicago) 0w40 is pretty much the way to go?

[632 Regal]

used to be mobil1 5w30 was the reccomended but since they came out with the 0w 40 thats the way now. on the bottles it even says recommended for europian vehicles and way surpasses our requirements :)


so if i'm using synthetic on my car (chicago) 0w40 is pretty much the way to go?

[cary]

Personally, I think the 10w-30 recommendation by BMW NA was a bad recommendation. The Mobil 1 10w-30 (all the mobil 1 30 weights in fact) are formulated on the thin side of the 30 weight scale, approx 10 cst @ 100c. BMW NA still recommends this when you call them, yet, it does not have ACEA A3 approval (important for valvtrain protection with an HTHS of 3.5 or higher), nor BMW LL-98 or LL-01 approval. Guess which oil has all three approvals? Mobil 1 0w-40. BMW NA is not with the program. Of course this is the same group that has pushed for 15,000 mile oil changes, which with a top quality synthetic like the Mobil 1, is right at the limit, but from the oil analysis I have seen is about 10-30% to far for the Group III base Castrol Syntec they sell.

Cary

[Hector]

the oil guru here. Him, Bill R and myself have discussed/arguered on this topic more than once in the past. Look in the archives. I'm for 0W-40...

[babalouies]

Any change in recommendation for a slightly more...ah..."heat intensive" environment like Texas? I'm currently running Mobil 1 15w50 synthetic based off of the local shop's recommendation.

[cary]

Hey Hector, I hope I don't step on any toes this time. ;) For the question about Texas, there is no problem with using the 15w-50, it is fine for all use in temps above 40F or so. I will say that even here in sunny CA, that I noticed that the lifters were much quiter at startup and the car burned less oil when I went from the 15w-50 to the 0w-40. However, I don't tend to take long trips in hot temps in the car. If I were doing a lot of driving in 100f+ weather, I would probably use the 15w-50 just because I am anal. The 0w-40 is more than adequate for all temps though. BTW, the 15w-50 while moderately thin 50 weight has a very high HTHS of 5.11, a sign of its very stable basestock.

Cary