"no" oil pressure on cold starts

The m10 powered e30 I daily drive is showing the dummy light for about 3-4 seconds after a cold start. After the first start, it's not an issue.

I have 20w-50 in there at the moment, non synthetic. I haven't changed the oil since I got the car, just been keeping track of it's look and feel via dipstick.

In a few days I will be on winter break and will change the oil. Any suggestions on weight/type etc given what I know?

Make sure the battery's in good shape, then pull the fuel pump fuse / ignition / both so it won't start, and give it a good long crank (like close to 30s). Does the light flicker or go off?

20W-50 is too heavy for Maine winter temps.

Oil weight aside, seeing the oil light for 3-5 seconds is very common on high mileage m10's and m30's.

I was gonna say the oil weight is much to heavy as well. should it be running like 5w40 or 10w40 or so? maybe 10w30?

I can't think of an M10 or M30 I've seen in the last 15 or so years that didn't keep the oil light on for a few seconds in cold temps. My 533i did that for all the years I DD'd it and ran to 238k miles with no oil-related problems.

Do not use oil lighter than 15w40 (5w40 synthetic is OK) in an M10 or M30 under any circumstances (at least below the Arctic Circle). 20w50 is good to around 0degF IIRC. What you really need to be careful about is that the oil filter seal and the filter itself can take the high start-up pressures; I've seen them blow and dump all the oil in seconds on cold mornings. Use ONLY factory, Mann, Mahle, or Hengst filters.

I've been topping it off with 15w50. I just remembered because I couldn't find 20w50 at my local autoparts place.

This is from the bentley manual.

First, get some 10-30 or 5-30 in that thing. 20-50 is way too thick for this time of year! YOul'll have about 10% less pressure when hot, but it won't hurt anything on the street.

I run an accusump in my expensive motors - so that I have oil pressure when I start. The other car has no choke and I can spin it a little before I pump the gas to start it, that way I have pressure.

MOST of the wear that little motor gets is during the time it runs with the oil light on, NOT GOOD (you know that, right?).

So, do your oil and filter - that should help. Good luck.

I have found that most older cars have the light on for a few seconds after starting. I have always wondered if it was the same thing as the temps.. that modern cars have their lights and gages "dummied" not to show things that look like problems until there really is a problem

mad_machine wrote: I have found that most older cars have the light on for a few seconds after starting. I have always wondered if it was the same thing as the temps.. that modern cars have their lights and gages "dummied" not to show things that look like problems until there really is a problem

The factory oil pressure switch on the M10 is set at the same level as more modern BMWs, at least up to the early 2000s - 7psi. Way too low IMHO, and in the opinion of many classic BMW owners, which is why many install a proper gauge.

The coolant temp gauges are buffered in more modern cars, however, which means things can go from fine to very expensive in very little time.

Taiden wrote: I've been topping it off with 15w50. I just remembered because I couldn't find 20w50 at my local autoparts place. This is from the bentley manual.

Is it 15w50 conventional or synthetic (I think Mobil1 makes a syn in that grade)? If the latter, you're absolutely fine, and if it's dino oil, you're still good unless you see really cold temps.

That chart is taken directly from BMW manuals of the era. Live by it; many, many BMW engines of that era have gone multiple hundreds of thousands of miles using those specs.

You realize he's in Maine, right?

Looks to me like the Bentley chart recommends 15w50 for ambient temps between 0F and 100F.

Last time I checked, 100F doesn't happen too often in Maine in Dec., and it is not unrealistic to expect temps lower than 0F.

If you're gonna live by the chart, I'm thinking 10w40 is better.

First off, relying on dummy lights is not a good thing. Spend a bit of cash and put in a nice mechanical guage. And yeah, 20w50 in really cold weather flows like molasses. Put a quart in your freezer for a while and try to pour it out. I'd switch to something thinner in winter.

SVreX wrote: You realize he's in Maine, right? Looks to me like the Bentley chart recommends 15w50 for ambient temps between 0F and 100F. Last time I checked, 100F doesn't happen too often in Maine in Dec., and it is not unrealistic to expect temps lower than 0F. If you're gonna live by the chart, I'm thinking 10w40 is better.

Depends where in Maine; coastal Maine doesn't get nearly as cold as inland.

Also bear in mind that "Special Oils" refers to synthetics; all the specific grade listings refer strictly to conventional oils. Hence my differentiation between the two.

Winter around here can be from 50f to -10f. That would put me at 10w-40 to 10w-30.

I've just always heard that the m10s love thicker oils.

Taiden wrote: Winter around here can be from 50f to -10f. That would put me at 10w-40 to 10w-30. I've just always heard that the m10s love thicker oils.

I ran 15w40 in my 533i (M30 - same oil specs as the M10) in only slightly warmer NY winters with absolutely no problems. If you want to be really totally completely safe, use a 5w40 synthetic (Rotella T6 is quite good and very popular with the BMW crowd), but IME 15w40 was perfectly fine for winter in the Northeast. Just make sure you don't cheap out on the filter.

What about something like a Mobil 1 High Mileage 10w-40?

Taiden wrote: What about something like a Mobil 1 High Mileage 10w-40?

The full synthetic version? Should be just fine; that's a very high viscosity 10w40, meets A3/B3, A3/B4. Pour point is -33F.

I think it's the synthetic blend

On my mercedes it takes about 5 seconds with the car running to show oil pressure on the mechanical gauge. I figure when the car sits the oil bleeds down from the gauge into the pan so it really isn't a "true" reading of oil pressure at startup since there is a lag.

The closer the sensor is to the pump the sooner the light should go off.

The point of the heavier oil is to lubricate rotating and sliding parts. If you are sucking an air pocket in the pan full of molasses, you are not providing any lubrication. Unless you plan on going to a track day at -10, I'd drop a couple of grades at least- synthetic 10w30 will work for daily driving. I have a few liters of Elf 5W50 synthetic at the shop for those track days, if need be.

that's one of the reasons I prefer electric gages.

That and they show immediate changes that the tube can't... and having had a gage leak, you do not have a source of hot oil inside the car with you

The M30 in my car will show the light for a second or two. As the oil gets older, it seems like the light will stay on a little longer. Change the oil and filter and see what happens.