which oil? - BMW Forum

quickmike · 10-05-2003, 09:46 PM

I've had my 1991 325i for about 2 weeks now and am getting the car ready for winter and was wondering which synthetic motor oil to use in it and what weight is best for the 2.5 L engine. It's between the Mobil synthetic and the Castrol synthetic. The winters here in the midwest range on average between 0 F and 40 F.
Any opinions on this would be greatly appreciated.

MrM3 · 10-05-2003, 10:02 PM

I use 10w-40 as do some other E30ers and that seems to work well, although i use castrol gtx high mileage (non-synthetic)

quickmike · 10-05-2003, 10:07 PM

So would the non-synthetic Castrol be better for a high mileage engine? I've got 182,000 miles on it with a slight tapping sound coming from under the valve cover and was thinking a synthetic oil might stop it from tapping (or maybe a valve adjustment?) im not sure.

Thanks for the opinion

MrM3 · 10-05-2003, 10:11 PM

Quote:

Originally posted by quickmike@Oct 5 2003, 10:47 PM
So would the non-synthetic Castrol be better for a high mileage engine? I've got 182,000 miles on it with a slight tapping sound coming from under the valve cover and was thinking a synthetic oil might stop it from tapping (or maybe a valve adjustment?) im not sure.

Thanks for the opinion

i dont know, i guess its worth a shot. non-syn oil is generally better for a higher mileage engine. i would also do a valve adjustment too.

quickmike · 10-05-2003, 10:20 PM

Cool thanks for the info!! As I learn more about this car I hope to help answer other peoples questions as well.

bimmerchic · 10-06-2003, 12:02 AM

Quote:

Originally posted by MrM3@Oct 5 2003, 10:42 PM
I use 10w-40 as do some other E30ers and that seems to work well, although i use castrol gtx high mileage (non-synthetic)

I use castrol gtx too!!!

kali*

m42technic · 10-07-2003, 04:49 AM

Non-synthetic oil isn't necessarily better for higher mileage motors. I run Mobil 1 synthetic in my car with 160k miles and I have no problems whatsoever. Just make sure that your engine seals are in reasonable condition.

Synthetic oil isn't going to solve your tapping noise though. Your M20 has mechanical lifters, so valve lash is only adjustable manually. Adjust your valves.

Pretty much just a matter of weather or not you want to spend the extra money for synthetic oil.

Fox · 10-07-2003, 11:09 AM

synthetic oils eat through old seals. Its incredibly thin and youll most likely have lots of leaks

m42technic · 10-08-2003, 01:17 AM

Quote:

Originally posted by Fox@Oct 7 2003, 09:49 AM
synthetic oils eat through old seals. Its incredibly thin and youll most likely have lots of leaks

Show me how this is true.

Fox · 10-09-2003, 03:13 PM

Go put some in an old chevelle see what happens.

m42technic · 10-09-2003, 03:53 PM

Quote:

Originally posted by m42technic@Oct 7 2003, 03:29 AM
Just make sure that your engine seals are in reasonable condition.

Weeeeeeeeee!!!