5w40 synthetic oil is an approved oil to use in my engine; it can be used year round. FYI, 5w40 is listed in the owner’s manual as safe to use and is also recommended for use when the temps go below zero. My self I think it should be used anytime the temps go below 10 above zero. On my next oil change I will be switching to Amsoil 5w30 HDD for year round use. BTW, I is my understanding that synthetic blend 5w40 is not an approved oil to use year round.

 

Salute!

Dunno?... while driving on an "ice road" using hand held GPS and also using cruise control set using tach rather then speedo( using speedo was out as I have both kph and mph which makes it harder to determine speed in mph as kph is the dominate)I found the following:

1600 rpm 57mph
170060
180063
190067
2000 70
seems at every 100rpm increase I'm consistantly getting another 3mphincrease (goes other way as well)

at 2500rpmmy speed was 87mph. I have been running amsoil synthetic oil for some time now. Oh and reason why I did this...
was racing co-workers 05 oh no (which was chipped with "hypertech" and lots of bragging!!) I let him get ahead of me (real cofindent ) any ways got er upover 110mph and blew his doors off... his passenger later told me... "he was cussin and slammin his fist into the dash and I was holdin on to the holy sheit handle the truck was rattlin so much!!" Cummins made me proud!!

One other thing had my OEM tires and rims on (265/70/17 cooper STT) as some punk kid had gone around the "hood" and slashed a bunch of tires mine as well!!![>:]