"High mileage" oil?

[Ross]

I accidentally bought M1 "high mileage" oil. I understand there is an additional additive package in this stuff intended to preserve seals.
What is the consensus here regarding the use of this in our BMs?
No current leaks, will this stuff swell seals and cause leaks?

[Bill R.]

and no problems so far... the valvoline high mileage one i've seen a few customers use it in old american iron with either a wick type rear main seal or the one piece rubber one and it actually helped to stop some leaks on the rear main on them. On european stuff that has a rear main leak ,usually when you pull the seal out the rubber is hardened enough that it cracks when you flex the seal, so i don't think it will help any on them , but i also don't think it will hurt.



I accidentally bought M1 "high mileage" oil. I understand there is an additional additive package in this stuff intended to preserve seals.
What is the consensus here regarding the use of this in our BMs?
No current leaks, will this stuff swell seals and cause leaks?