# 1991 735il oil recommendation and door check question



## NC BMW Driver (Feb 1, 2008)

I recently purchased a 1991 735il with 79000 miles on it. Overall condition is very good, but I have a couple of questions regarding the car.

First, what is the recommended oil? I have always used dino oil. Is this engine suitable for synthetic oil? If so, what oil manufacturers are recommended?

Second, the door check strap attachment to the body has ripped out on the drivers side. I understand that there is a kit to fix this situation. How hard it it to install and what is the part number (if available)? 

Thanks in advance.


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## 04SSHD (May 29, 2006)

NC BMW Driver said:


> I recently purchased a 1991 735il with 79000 miles on it. Overall condition is very good, but I have a couple of questions regarding the car.
> 
> First, what is the recommended oil? I have always used dino oil. Is this engine suitable for synthetic oil? If so, what oil manufacturers are recommended?
> 
> ...


Synthetic won't hurt, I personally go with Mobil 1 10w30 in my car.


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## NC BMW Driver (Feb 1, 2008)

04SSHD said:


> Synthetic won't hurt, I personally go with Mobil 1 10w30 in my car.


Thanks for the response.


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## crewdog843 (Mar 15, 2006)

Once you decide to go with synthetic, stay with it. BMW recommends 10W-30 for your temperature range...but during the winter, a 5W-30 would not hurt, just makes it easier for your car to crank on those cold mornings. Once the engine heats up, the consistency goes to that of a 30 weight oil.

Can not offer advice on the door check strap, is any metal work damaged/in need of repair.

jake


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## NC BMW Driver (Feb 1, 2008)

crewdog843 said:


> Once you decide to go with synthetic, stay with it. BMW recommends 10W-30 for your temperature range...but during the winter, a 5W-30 would not hurt, just makes it easier for your car to crank on those cold mornings. Once the engine heats up, the consistency goes to that of a 30 weight oil.


Thanks - Next oil change it will be done. Why do you say that once you change to synthetic to stay with it?



> Can not offer advice on the door check strap, is any metal work damaged/in need of repair.
> 
> jake


Attached is a photo (I hope) of the check strap attachment. It has ripped from the door post. I understand that this is not unknown to have happen and that there is a fix for it that does not involve welding, etc., but I have not been able to get any details on what is involved.


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## crewdog843 (Mar 15, 2006)

Something I have heard from the days when I used dino fluids in my engine, has something to do with holding contaminants in suspension versus letting them sink to the bottom of the sump (or other low spots in the engine), creating 'sludge'. Years ago, there were only single weight oils and they were non-detergent, and shortly after the detergent oils appeared on the scene, synthetic oils also appeared. When I made the decision to go with synthetic, I believe my mechanic advised me not to go back to non-synthetic, and I took his advice seriously.

I can remember engines (first one I ever worked on: '49 Ford flathead) completely glued together by what looked like tar...before you could do anything to them, you had to clean them with gasoline just to get to the part you needed to work on. Messy business. Today, if you look at an engine which has had regular oil changes, it will look a 'golden' color, and all parts will be very clearly defined and visible.

jake


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