Mobil1 0W-40 users: will you be switching your oil to a heavier weight for summer?

No! Why? Protection is required at start and higher numbers do not mean better protection at higher temps. I suggest you read the huge volume of postings on this subject which inlcude some quite learned dissertations on the many misconceptions about the oil numbers. Some guys run 0-20 oil year round.

 

I don't believe that is neccessary, unless maybe if you are planning on tracking the car. The 0W-40 gives you great protection at start up, especially for a 12-cylinder car, thus will be just fine for an 8-cylinder. And the 0W-40 is well within the specification of what the factory recommendations are in the manual. Switching from one grade to another is just a waste of time and money with no real benefits.

PS: Look at Dr.Aheaas' thread below on the different oil's stats, and do a search on his oil threads. Very informative and educational. Then make your own decision.

 

I see no reason to. The factory recommends the 5w-40 as the thickest viscosity the car needs, why would I want to switch to a 50 or 60 weight? What benefit would this give? For now, I see the 0w-40 as covering any forseeable temperature (street driving) situation I will be in. Which varies from winter in Seattle of mid/upper 20's to 100-105 in Eastern Washington State.

 

I'm not going to change. I currently see 6 bars of pressure at around 2,000 RPM with 0w-40 when the engine is warmed up. Oil temp stays below 100 degrees Celcius with the driving I've done, and the outside temp was close to 90 degrees last week.

Pressure is just a little lower at idle than when it had 15w-50 in it, but not enough to cause me any concern.

 

Quite a few of the later cars will peg the oil temp gauge when driven on the track and I have seen street driven 355's on hot summer days get the idle oil pressure so low that the oil pressure warning light comes on. In those sorts of uses Ferrari suggested the use of 10-60 and made the Shell product available to the dealers. If I was using the car in such a way that I was getting oil temps in the 300 degree range I would not be doing it with a 5-40.