300,000mi + 95 Legacy

[88coupe]

My 95 Legacy recently rolled over 300k and im about due for a oil change also trans/diff. I have changed oil with 15-40w last couple times and added some Marvel mystery oil. I went with 15-40w due to the high miles with no issues & before I used 10-40w no problems. My question is should I stick with the 15-40w dino oil or should I change viscosity and/or to a full synthetic/blend? I have read a few guys use the 15-40w in there cars and a shop my friend worked at would use 15-40w in all the older EJ22's & 25's that went thru. But I've recently read that 15-40w doesn't lube as well as thinner oils & that the cleaners in it can be harmful to non-diesel engines.

 

Also what are your idea's about adding a little 80-140w to the 75-90w(80-90w) for the trans/diff to help cushion older parts?Or Is there a good additive to use for this?

[lmdew]

5w-30 is what I use in my 98 Impreza with 320K.  I would stay with regular dino oil.  No need to switch and it will most likely cause problems not prevent them.

 

Quality lube has all the essentials to prevent wear.

[heartless]

there is a lot of controversy over the dino - vs - synthetic thing. doing a search will get you lots of reading material. personally, I would stay with what has been run in the car for the majority of its life - in your case the dino oil.

 

initial start-up is where viscosity plays the biggest role. depending on where you live, and the average temperatures, the 15w40 may be too thick - the colder the temps are, the thicker the oil will be, the less able to flow easily at cold startup when it is most critical.

 

If you still have the owners manual for the car, it will give you recommended oil viscosities for various temperature ranges. Use a good quality oil of the recommended viscosity.

I switched my 95 Legacy with a little over 200K to a "high mileage" version.