Oil Question!

Yes, I have searched the forums and have also read the LNE Oil Memo. However, my 03 C2 Cab is a daily driver and I live in AZ where our ambient temps are much higher than most. Currently using Mobil 1 15w 50. I really don't need to get into the "Which brand is better" conversation , but from what I have ready, the 15w is probably the best choice for my specific situation considering both the heat and the fact I drive the car alot. Thoughts?

5W50

I can tell you from trying everything use only Mobile 1 0w40. My coolant temp is at its lowest with 0W40. My temp gauge sat on the right side of the 0 in 180 with 15w50. It sits in the middle of the 8 and the 0 with 0w40. Change your oil every 5k miles or 6 months, whichever comes first. I live in the valley too and it gets hotter than the hinges of hell here! It was a balmy 105 today.

I only drive my car in the summer when it's warmer, so I use 15w50, which I believe protects the bearings better. Just my 2 cents.

May sound silly but I'd call these folks. See what they use. Dabbab Street Al Sulaimania Area Near Altamimi Safeway PO Box 58295 Riyadh 11594 Kingdom of Saudi Arabia Telephone: +966 1 466 7788 Fax: +966 1 466 6911 Telephone: +966 1 466 6647 Fax: +966 1 416 3067 Opening hours: Saturday - Thursday 9:00 am - 12:30 pm 4:30 pm - 9:00 pm Saturday - Wednesday 7.30 am - 12.00 pm 1.00 pm - 5.00 pm Thursday 7.30 am - 1.30 pm E-mail address: [email removed] Postal address: SAMACO Group P.O. Box 11931 Jeddah 21463 Kingdom of Saudi Arabia

Quotes source post: 9537707

Interesting. Just sent them an email. Will let you know if I hear back.

A Shell rep gave a presentation one time and made the point that thicker oils don't give more protection...it's the flow of oil that protects. He suggested always using the thinnest oil, recommended by your auto manufacturer, that would give you adequate oil pressure. He said their tests show that gives you the best oil protection & lubrication. So... I'd go 0W40 or 5W40.

Quotes source post: 9537756

Bingo. Oil viscosity that is appropriate for an engine is based on the engine's clearances. Generally engines built to larger clearances require a heavier oil to provide a safe oil pressure. A heavier oil in an engine built to tighter clerances -- and most street engines are built to fairly tight clearances because engines with tighter clearances are quieter and last longer (a looser engine will often emit a deep bass knock when first started and until oil flows and pressure builds) -- can raise engine oil temps due to the friction of the thicker oil adding to the temp of the oil. Sincerely, Macster.

We don't need another oil thread, that's for sure, but since you asked... Macster is right on. One of the first things that come up in a basic tribology course is that viscosity has NOTHING to do with film shear strength or protection. Using that same logic, why not just use straight 50 weight oil. Thicker is better, isn't it?. Sounds stupid, right? I mean, that's obviously, too thick, right? Well, so is 15w-50, for our particular engine. Your engine oil, unlike the air cooled engines, really doesnt care much about the 20 degree difference between 90 and 110F, your cooling system does. It does care if you run at 2k RPM or 6kRPM all the time, where oil FLOW is critical. Getting the heat away from that shear location is far more important than the hypothetical differences between certain oils. When the oil is 70 or 80F and starts at 15W, it ain't flowing like it should in the spaces that need it most. So until the engine comes up to temp, you've got more wear than you should going on. The general charts that show what oil ranges are used in what temperatures, always show just that, ranges. There is no consideration given to the particular engine in question. In fact, there is always some sort of reference like "Use the oil weight recommended by the manufacturer" or some such. If Porsche prints that 15W-50 is fine for the 996, when ambient temps are 70 to 110, then fine, use it. But AFAIK, they still only show around 0W-40 or 5W-40 for the commonly found oils, here in the US. If I lived in heat like yours, I'd be looking at a lower temp T-stat or a 3rd radiator install, not using thicker oils in an engine not designed for that weight. While not a Tribologist, I took 2 Masters courses in Tribology, and talked to lubrication experts. Just sharing what I was taught, long before the 996 came out.

+1 to the Macster and perryinva. Forgive us...those with l-o-n-g auto histories have trouble abandoning our earlier lessons; i.e., high viscosity is always better. Today's engines AND advanced synthetic oils require new attitudes. And ignoring the manu.'s current recommendations is a risky strategy. relinuca