Now,That the summer is almost here.Should I change from 10/30 to 20/50 ? I've been using Castrol religeously,but if there is a better product (available at my local auto shop)that could be recommended,I would certainly try it.I've also read in these posts that Redline Synthetic,MTL or MT90 are all good for tranny & 75/90 for the differential.Thanks :notify:

 

I would just suggest sticking with the 20/50, its rated up to 120 degrees in the Hayes manual.

Not to sure about tranny, I'm just about to change mine since its to notchy, and the rear end just use whats approved for limited slip diffs and stuff.

 

You'll hear a lot of people recommend 20/50, however, it really depends on you climate. If it's in the 80 to 90 range or hotter thrugh the summer, the heavier oil is OK. If it's a little cooler, like 70's to low 80's most of the time, 10/30 is all you need (remember, mazda actually recommends 10/30) - IMO, cold starts in a cooler climate with heavier oil is not very good for your motor. Castrol seems to be the choice of many but then again, I've read a lot about Havoline being a better oil. I use 10/30 Havoline and the opinion above reflects that - either of the above will do your motor no harm - hjust don'r use 5/30 or 10/40.. too many detergents and they won't burn as clean. MT90 redline is an excellent product for your tranny, especially if you have scratchy synchro's

 

Maybe I should just stick with the 10/30(I change it every 2,000 km), 'cause some mornings it is pretty cold.I also find it sometimes is hard to start after being rained on all night.