blend M1 0w40 & M1 15w50?

[Russell]

What do you think of a blend of three quarts each of M1 0w40 & M1 15w50? in a 1995 BMW 2.5 liter M50 engine with 122,000 miles? I think this would be 7.5w45 oil.

Older BMWs tend to like heavier oil,yet the hydralic lifers on the M50 engines likes lower weight oil on a cold weather first start. BTW, I use no oil.

Just a thought at this point

 

[racer12306]

since you want a thick oil with good cold flow, what about castrol syntec 5w50.

i have heard others mention that when mixing you should stay with similar oils, like supersyn with supersyn and ep with ep. and since 15w50 is only available in ep now it may not be favorable to some but it may be fine.

i know there is a viscosity calulator around here, ill look for it and report back with actual viscosities at 40* and 100*

 

[racer12306]

i found the calculator, with a 50/50 mix of M1 EP 15w50 and M1 0w40. the oil will have a viscosity of 102.5 cSt @ 40*C and 16.1 cSt @ 100*C.

according to the BITOG viscosity chart that viscosity is a thick 40 weight oil when up to temp. but i dont know how the cold flow stacks up. it is thicker than M1 10w30 at 40*C.

 

[Russell]

Racer,
I may very well go with castrol 5w50 or the castrol 5w40 after I finish my second Auto-RX rinse.

FYI, valves really rattle (for a few seconds) on cold start with even a 10 weight oil

 

[racer12306]

wow, sounds like a pretty picky engine.

 

[Russell]

I tend to agree when it comes to oil. It also likes 93 octane Chevron gas since I installed a performance chip.

FYI,it has 10.5 compression with two knock sensors with individual coils for each cylinder. However, 30,000 miles on last set of plugs revealed very little wear with minimal tan deposits and does not use any oil at 122,000 miles.