Vortec 4.3l v6 oil recommendation

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I have a 2001 GMC Sonoma 4wd with 135,000 miles. The trucks oci has been 3-4 k miles since purchasing with cheapest api Dino 5w-30 oil. I live in the high rocky mountains and I expect temperatures to get well into the negatives this winter. I drive a whole lot. It is common for me to put 3-5k miles in 1-2 months. Often times towing a 1300 pound trailer with about 400 in the bed. I get nervous sometimes as my oil pressure gauge always reads about 40psi no matter the rpm unless idling. But sometimes I have to be WOT for 5-8 minutes going up some mountains, and my oil pressure will drop down to about 35-38.

Im looking to hear what people would recommend for me, as my goals are to extend oci, have good low temperature flow, and make sure my oil pressure is not to low in extreme towing conditions. Thanks
 
I would start at 7,500 miles or 2 years, and if possible a used oil analysis would let you know how much further you could go.

If you are interested in extending drains the Mobil 1 0w40 will go further, but either would work great.

I'd recommend a Fram Tough Guard for up to 10,000 miles or Fram Ultra for up to 15,000 miles. If you change your oil every 7,500 miles you could use the Fram Ultra for 2 oil changes like i do, just leave the filter on and don't touch it. They are one of the best filters you can buy.
 
WOT for 5-8 minutes going up a mountain while towing? 0W-40 M1 might be a great choice. Other than what you're doing, that motor is really easy on oil. With mostly highway driving, even towing, you could probably go 10k OCI easy - keep it topped off. M1 OW-40 is cheap at Walmart - buy 2 jugs - one for top offs.
 
Originally Posted By: bigt61
WOT for 5-8 minutes going up a mountain while towing? 0W-40 M1 might be a great choice. Other than what you're doing, that motor is really easy on oil. With mostly highway driving, even towing, you could probably go 10k OCI easy - keep it topped off. M1 OW-40 is cheap at Walmart - buy 2 jugs - one for top offs.


Agreed with this and the ATF. Have you considered a trans cooler or installing a beefed up version? That kind of extremes can destroy even the highest quality ATFs
 
If the transmission is regularly serviced, every 30,000 miles is good. I recommend Maxlife full synthetic dex/merc.

You can find it at Some Autozones, Walmarts, Meijers in gallon jugs.
 
Hadn't thought about the transmission. I changed filter and fluid on that about 15,000 miles ago and I planned on doing every 30,000. I also am pretty sure I do not have a trans cooler.
 
Synthetic 5w30 at 7500 miles OCI will suffice in Ur truck. I would replace the tranny filter w oem and go with dex VI fluid. Also don't forget the transfer case and differential fluids.
 
U can go at least 4x longer on the differential fluid. It appears u are doing Ur truck a favor with ur maintenance schedule. Should last a very long time
 
Originally Posted By: gmgoodwrencher
Currently my truck came with a OEM oil guage what's one of the easiest ways to make sure that's accurate?


Note that I typically will tee into a sending unit or some other oil gallery fitting and use a real pressure gauge for a day or two just to compare it to the factory readout.

On our GM V8 fleet trucks the gauges are surprisingly accurate until the sending unit starts to fail...
 
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