I just purchased a Old 1985 BMW 318i. It's got 230,000 miles on it but it's still a really tight car and well maintained. I purchased the car from a private seller and He had been running 20w50 motor oil in the car. I found that quite strange. I took it to get the Oil changed and the place only had 20w50 in synthetic and I didn't want synthetic so he offered to put in 15w45.

I asked them why such a heavy oil was being used in my car and they told me that some people think it makes the cars last longer but it's actually worse for them because the oil is so heavy it doesn't splash around on start up and doesn't provide enough lubercation. He convinced me to go with 5w30 Because it's getting to be winter here in Minnesota and we do have problems with starting vehicles in the cold.

There will be times where I will have to keep the car outdoors in the winter for 8 to 9 hours at a time while i'm at work and I'm worried that the heavy oil will prevent my car from starting. I don't have a second car so I have to use it all year round. I know in my company Trucks we can have troubles with even 10w30 motor oil starting in the winter.

I just wanted to ask around and find out if this 20w50 oil is a myth or if I should change my oil with it everytime. Any advice would be appreciated. I plan on restoring the car in the next couple years but i want the current engine and transmission to be good until then.

Actually people put heavyer oil into their cars so it doesnt get past the blow out valve seats and/or piston rings. One thing you might wana check is, take the spark plugs out and see if their coated in oil. If they are then you got some problems. I would suggest 15/30 for you. I use it in all my cars.

Yeah, I think it's probably the Oil now. I went to start it and it ran alright for a bit then boged down and stoped on the side of the road. I couldn't get it started again for about 15 minutes and when I got it going again it wouldn't stay running for very long. At first I thought it was flooded but it will turn over sometimes. Even if I keep the gas on it and hold it at 1500 RPMs the engine eventually cuts out anytime from the moment it starts to a couple minutes. I haven't checked the spark plugs just yet. I'm about to go do that now. Looks like i'm going to have to get some of that heavyer oil and and rechange the oil and get new spark plugs. I guess that's the last time I trust the people at the oil change place.

The oil weight will not affect the engines operation.

Not now, not ever.

The issues is a temperature range that the ECU is not getting the signal it expects.

I would be suspect of the engine ECU temperature sensor.

BMW did a coolant recall where they added a small valve in the system.

It is powered by the wire to the ECU temperature sensor so as this added valve gets older it affects the signal from the sensor.

If it is the added valve a green 30amp bladed fuse fits the connector to bypass this valve.

Ether way you need to take this car to a real deal mechanic.

Guessing can cost alot of money in parts and tow bills.

Later,

That's interesting. I didn't think of that. THe Radator has been replaced recently but I'll have to look through the records and see if This has ever been replaced. It's kind of strange that it started happening so suddenly.

When I turn on the Car is there something I should look for? like a Certain temp that causes the car to shut off?

Well I checked the Spark Plugs and no signs of oil So i'm ruling out the oil doing it. The Car starts fine and drives fine. I drove it around the block for about 30 minutes with no problems. I parked it in my driveway and let it idle it quit out after about 2 minutes of idling there. SO the problem has something to do with it idling. I also noticed that is Idles Irratically. Bounces between 1000 and 700 RPMs. I'm going to replace the fuel filter because that's cheap and I can do my self but not convinced that's the problem.