Originally Posted By: PDX2500HD
Correct me if I'm wrong, but synthetics also hold up better under extreme heat (115 degree day in Phoenix, towing 15,000 trailer, and in traffic for example).. Which is very possible. I have a home in phoenix, and have lived there 10 years... I've seen the transmission temps spike past 170 degrees just idling in traffic on a friends 2007 Dmax.. that's without a trailer or high rpm loads.. Why take the risk if for $30 more, the technology is there to get cheap insurance?
Are you wrong? No - you are not. But your perception of what is "hot" is wrong.
Yes, syntheics can protect "better" against heat. But the "heat" at which they succeed where a dino would fail is well above "normal" operation of a vehicle. Further, the range where a synthetic would be safe and a dino would not is a fairly narrow one, and is a passing moment on the way to equipment failure.
If you expernience a cooling system failure, the dino fluid would fail fairly quickly. A synthetic might prolong that occurence by less than a minute. But eventually, even that synthetic is going to get cooked. If your cooling system fails, and you continue to run, NO OIL REGARDLESS OF BASE STOCK will save your engine, regardless how many oils you've seen in a frying pan on TV.
And don't for one second start down the "but it's a turbo diesel and it gets hot in the turbo" alley, either. Turbo cooling is a matter of heat reduction via thermal transfer. As long as the oil is flowing as designed, the rate of transfer, even during a long hard pull, is sufficient to cool the turbo. The OEM engineers designed it as such. The Dmax, in particular, is probably one of the most trouble-free engines in the light duty truck market. You are not going to "cook" your turbo by using dino oil, or save your turbo from demise, should a true failure happen. If you don't understand the concept of thermal transfer as it relates to time, then here's a very simple little experiment for you ...
1) light a candle
2) run your fingers quickly over the candle, and you won't feel much heat, if any (your finger did absorb some heat, but it wasn't much due to the small time exposure)
3) pass your fingers slowly over the candle, and you'll feel some heat; it will be uncomfortble, but managable (your finger absorbed more heat, but not a dangerous amount)
4) hold your fingers over the candle until they burn (here, damage has occured to your flesh because your blood was not able to carry away enough heat to cool the skin to a sufficient level)
Get the point? As long as the oil is moving through a turbo housing, even at full tilt, the OEM design is sufficient to carry away heat without burning the oil. Synthetics cannot carry away more heat than a dino because synthetics can only flow at the very same rate and volume as the dino; oil flow is a matter of design of the lube system, not the base stock of the oil. Thermal transfer is a matter of coefficients of heat rejection and volume and flow rate. Period. NOTE: There is one time when you do need to be concerned about turbo heat soaking into the oil and that is at shutdown. You should NEVER shut down a turbo immediately after a long heat soak, regardless of engine fuel type or oil base stock. ALWAYS allow a turbo engine to idle for a few minutes rather than shut it down after a long hard pull. Normal driving is not an issue, but pulling a long grade uphill for 5 minutes and shutting the engine down at the top of the mountain for a scenic picture is not a good idea. Let the engine idle, and the oil will continue its job of "thermal transfer" safely.
Now, I would agree that synthetics also resist oxidation and evaporation a bit better than dino oils, but this is eaisly negated with (you guessed it!) OCI duration. And since the OP already stated that long OCIs are not his thing, then these two points are moot in his application.
A Dmax is an liquid cooled engine; unless there is a cooling system failure, your temps are regulated to around 210 deg F. That is by design. Believe it or not, oil temps can actually be too cold at times. You want the oil to get up to temp as quickly as possible, and then stay there as long as possible. The heat of AZ is not an issue that most would believe. For an air cooled motor, perhaps. But not a diesel truck with a good towing package. I actually want my engine to to be between 200-210 F all the time; that is the proper operating temp range. I have NEVER seen mine go over 215 F, even when towing.
As for the transmission, 170 deg F is not hot either. Those of us that tow frequently in hot climates and mountainous places, will often see 180-200 deg F as the norm, and it can spike to around 225 deg F in long pulls uphill, and perhaps a bit more. But that is not "too hot" for the fluids. Fluids degrade not just with heat, but the time in combination with heat. Being up to 250 deg F is not even a danger if it is brief. Is it desireable? No, it's not. But it's not a death knell either. I saw my transmission get up to 210 deg F once, pulling across SD in 98 deg F OAT, into a massive headwind at 75 mph travel speed. Considering that the red-line on the transmission gage is 275 def F, I really wasn't anywhere near the danger zone.
So, yes, synthetics can tolerate heat better than dino oils. But no, it really doesn't make much difference in the real world given your conditions and the design of the Dmax vehicle.
Now, once again, I agree that synthetics are good products, but only when used with the understanding of both their benefits and limitations. I use synthetics in my truck; I have Mobil 1 in the diffs, Mobil 1 in the t-case, and AutoTrans-5 in the transmission. But I use those because the OCIs I intend to put them through are long, and the payoff is there; I can get the ROI. The synthetics are not "better"; rather, they last "longer".
