i use mobil 1 20-50

In the sticky at the top of the page, Mazda reccommends 20-50 for temps between 0 - 80, so thats what I use, cause it never gets below 30* F all year, sometimes we will see a hot day here and there

My owners manual calls for 10w-40 year round and I typically use that in the summer and switch to a 5w-40 in the winter.

Contrary to popular belief ring land wear that was associated with older blends of 10w-40 oil is not an issue for our ringless engines. The ash issue isn't much of a problem either with oils with large vicsocity spreads since EPA and API are heading towards low SAP oils to reduce toxicity to catalytic converters.

I did run 20-50 once in the summer and it cost me about 2 mpg in fuel economy. That doesn't sound like much but is a 10% decline.

I am glad this topic was brought up. Its not one that is mentioned much and is important.

It is interesting you say that homebrewer, since it seems on this message board, in the FAQ and many members, tend to stick to the 10w-40 being bad for the rotary, like gospel. It seems to be stated as a fact by a few resources I have found online, and many times saying the FSM's suggestion of 10w-40 is dated, and inaccurate. Admitedly it scared me away from using it, even though I usually follow FSM's pretty strictly.

Since you have been using it, can I ask how long you have used it? I would assume you have been trouble free?

i live in Ca, bayarea, it stays at about 60-80 most of the year, sometimes it gets up tehre but not often, i use 10w-40 GTX, i havent had any problems

what would you guys recommend for tucson az? its more like... 90-110 (110 being max during summer), but.. 5-6 months of the year its basically 90+

20W50 will work for you year-round.

I've used 10W-30 all year long, the engine in my car has been on 10W-30 all year long and it's at 83,000 miles and doesn't smoke a puff...

Thats fine, and I've read that many people are using 10w-30 as an alternative to 10w-40, which seems to have been shunned. My question is, is 10w-40 really not bad at all, is the whole thing a myth?

Okay we don't need another thread on this... there are at least one a month and it is also covered in the FAQ for FC sticky thread found at the top of this section.

Oil questions other than weight (like the formulations and additives used in high spread visositys) to be used in a FC (which again is covered in the FAQ for FC sticky thread) should be brought up on a Oil board such as Bob the Oil guys board and others.

Thread closed. Covered only about a billion times here, and in the FAQ for FC sticky thread.