Oil for an E30 M3?

[donnymarcos]

Hi all, this question was asked 6 years ago so I thought I'd revisit it.

Trying to choose the best oil for an '88 E30 M3.

For the unfamiliar, it's got a high-strung 4-cyl engine that revs to 8,000 and has a operating oil temp of 180-250*F or so. This is a weekend fun car - not a daily, but I do like to flog it when I do drive it.

My particular engine has about 250k on the clock and runs well, so I'd like to squeeze as much life out of the engine as I can. These engines are notorious for trashing rod bearings and blowing seals. They are also amazingly expensive to rebuild.

Factory recommended weight when the car was new was 15w40 or 15w50. My understanding is that a couple years ago BMW changed the recommended oil weight to a 0w40 for all its older cars.

Among the owners, I see two opinions:

1) Pick a 40-50 weight oil with the lowest cold viscosity, i.e. a 0w40.

2) The high temps of the engine burn off any friction modifiers, so stay with a higher-weight oil, 15w40 to 20w50.

I know that ZDDP is a must, as it's a flat tappet engine.

My instinct is to pick a 0w40 oil like Mobil 1, in order to reduce wear on startup. But being as this is an old engine that is also pretty stressed, I don't want to pick something that's going to inadequately protect the engine.

Should also mention that I live in Los Angeles.

What do you guys think?

 

[JHZR2]

IMO the cold temperature limits have not changed. The quality of the oils at higher temperatures allows creepage of lighter oils into heavier - spec regimes (higher temperature use).

In LA, if you are driving hard, Id still consider M1 15w-50. The climate is right for it, and it will provide very strong performance.

0w-40 is a fairly light 40wt, so despite ACEA A3 rating, youll need to watch closely for consumption.

5w40 HDEOs and maybe M1 10w-40 HM are good options.

 

[d00df00d]

to BITOG!

I'd strongly recommend oil analysis. Get at least a Dyson RAW service or equivalent test package; if the lab uses ICP spectroscopy, order a PQ index test as well.

What oils have you tried thus far? Any reason to suspect they're not doing the job?

Do you have an oil pressure gauge, or just oil temperature?

 

[demarpaint]

A bit OT but.......I always wondered why 5W30 for example on this chart doesn't go up as high in the temp range as the 10W30 does? I realize it is better in the cold than 10W30 but should handle the higher temps just as well as 10W30 does.

I guess in 1988 oil sheared more than it does today, but even the charts I've seen today are similar.

 

[BMWTurboDzl]

Castrol TWS for some reason came to mind. It's 10w-60. I'm not aware of BMW back spec to 0w40 since their relationship is with Castrol and Castrol doesn't make an oil in the US with that weight. Now many BMW dealerships sell a BMW labeled 10w-40 for "older" cars. Try them first?

 

[Rand]

Where did "the high temps burn off Friction modifiers" come from? Some of the lighter oil can burn off.. but not really the additives. You could also consider a specialty oil like redline. It would definitely be superior for app's like yours.

Sticking to oil available at walmart...
I'd say M1 0w40 should work well but I'd stick with m1 15w50 in your location esp if you see anywhere near/above 250F


0w40 is barely a 40wt after a few thousand miles.. perhaps even a high 30wt.. which is great for some engines.. not so sure about yours.

 

[zyxelenator]

For zzdp boost you can try SynMax oils. They have 5w-50 and 5w-40. Search VOA section, I did analysis not so long ago. They have serious load of zinc.
Amsoil have high zinc oils, valvoline...

 

[fxrider]

Mobil-1 15W50 would be my choice.. maybe Shell Rottella T6 5W40 in the winter. Both top Synthetic oils.

 

[Norm Olt]

20W-50 goes from below freezing to +120 degrees f on the chart.

In Socal when do you ever exceed these "limitations"?

A 15W-40 HDEO would be a great choice as well, especially if you anticipated zero anytime soon.

Cheers!

p.s. Seriously, AMSOIL AME or the M1 15W-50 mentioned would be just great. There is also NAPA's Synthetic 15W-50 on sale around here for $3.49 per quart.

I'd stock up.

 

[OVERKILL]

Delvac 1 5w40 is another choice/Mobil 1 TDT 5w40.

 

[donnymarcos]

Thanks for the welcome!

I just got this car so I haven't been using any particular oil. Just want to know what to fill it with for my first oil change. Analysis is definitely going to happen - if only just to see if my rod bearings are coming apart.

Unfortunately, this car only has an oil temp gauge, and not an oil pressure one - just the idiot light.

 

[donnymarcos]

The "friction modifier" thing was something I'd read on the forums for this car. In other words, the idea that a 0w40 oil had "thickeners" that once burned off, would result in a much lighter oil. Which would be a bad idea in a 250k engine designed some 30 years ago.

I've read the hypothesis that lower winter weight = better, because it gets moving in the engine more quickly and reduces startup wear - which, considering this engine's appetite for bearings, seemed like a good thing. Is that even the current thinking anymore? For some reason I thought a synthetic was built to the high-temp rating, then modifiers added to keep it viscous at lower temps...

 

[d00df00d]

Originally Posted By: donnymarcos
The "friction modifier" thing was something I'd read on the forums for this car. In other words, the idea that a 0w40 oil had "thickeners" that once burned off, would result in a much lighter oil. Which would be a bad idea in a 250k engine designed some 30 years ago.

"Thickener" is a simplistic word for a viscosity index improver (a.k.a. VII). That's not at all the same thing as a friction modifier. Just FYI.

VIIs don't really "burn" off except in turbos, which are WAY hotter than anything in your engine. What they can do is shear, either chemically (e.g. if fuel is slipping past your rings into your oil) or by mechanical force. The result would indeed be an oil that is thinner at high temps than it would have been normally.

Yes, Mobil 1 0w-40 has been known to shear in the past, although it's not quite clear whether the shearing most people have observed has been chemical or mechanical. It's still one of their flagship products, still carries more high performance OEM approvals than anything on the shelf (except maybe the new Castrol 5w-40), and is still used in ALL gas-powered cars from Porsche and Mercedes -- from the lowly C-class and Boxster all the way up to the AMG cars and the turbo 911s. Plus, I imagine you're running fairly short oil change intervals (in terms of miles). I wouldn't sweat the shear thing too much.

That said, I can't imagine you could go wrong with many of the other synthetic xw-40 and xw-50 products that have been mentioned so far.

One thing to remember is that VIIs have come quite a long way in recent years. My car fuel dilutes like crazy, and I have used two different 5w-40s in it -- one from Motul, and one from a bunch of very nice people on a farm in Ohio (RLI) -- that have shown no shear at all. Zero.


Originally Posted By: donnymarcos
I've read the hypothesis that lower winter weight = better, because it gets moving in the engine more quickly and reduces startup wear - which, considering this engine's appetite for bearings, seemed like a good thing. Is that even the current thinking anymore?

Yes -- IF the oil still retains enough viscosity and is sufficiently shear-resistant at high temps to do its job.


Originally Posted By: donnymarcos
For some reason I thought a synthetic was built to the high-temp rating, then modifiers added to keep it viscous at lower temps...

You might be thinking of pour point depressants. Those simply lower the temperature at which the oil no longer pours. Pour point is not really a meaningful metric; an oil could have a low pour point and terrible cold viscosity, or it could have a high pour point and excellent cold viscosity.

 

[donnymarcos]

Ok, cool. I had thought that going with a 0w or 5w oil was going to significantly reduce wear on engine startup because it flows better when cold. But it sounds like maybe that's not as big a deal as I thought. Glad I have options! Sounds like a few analyses can go a long way in determining what oil works best for you (that or not worrying about it!).

 

[d00df00d]

Originally Posted By: donnymarcos
Ok, cool. I had thought that going with a 0w or 5w oil was going to significantly reduce wear on engine startup because it flows better when cold. But it sounds like maybe that's not as big a deal as I thought.

Not so fast. 0w and 5w (and 10w, and 15w, etc.) aren't about pour point. They are about cold pumpability, which is a vastly more meaningful measure. It's still reasonable to expect to derive some cold-start benefit from a 0w or 5w vs. a 10w or 15w.

That said, the confusing thing is that the lower W numbers don't necessarily represent lower cold viscosity (although they usually correlate with it). Each one represents a measurement at a different temperature, most of which are below what you'll ever see in Cali.

"Lower is better" is best considered a rule of thumb.


Originally Posted By: donnymarcos
Glad I have options! Sounds like a few analyses can go a long way in determining what oil works best for you (that or not worrying about it!).

Pretty much.

Just remember: if you really want to use oil analysis to pick oils, you need to get a good test package as I mentioned in my previous post. The $20 ones that most people get (from Blackstone etc.) don't give you the info you need to make the call.

 

[Norm Olt]

https://bobistheoilguy.com/forums/graemlins/wink.gif[/IMG]

"...lowly C-Class and Boxter", eh?

How's about a 2011 C63 AMG with 451 hp and/or an old 2006 C55 with a 4.9 sec 0-60 mph time?

Smokin'!!!

Cheers!

p.s. I'm not usually big on Porsches but a 2003 3.2L Boxter S with 258 hp will flat run away from a lot of 911's...